Patchworkβ [1/2] IPMI/ACPI: Locate the IPMI system interface in ACPI namespace

From: Zhao Yakui <yakui.zhao@intel.com>

According to the IPMI 2.0 spec the IPMI system interface can be located with
ACPI. One is located in SPMI table(Service Processor Management Interface
table). Another is located in ACPI namespace.
This patch is to locate the IPMI system interface in ACPI namespace and
register it.
It includes the following two steps:
   1. enumerate the ACPI device tree to find the IPMI system interface
	The IPMI device type is IPI0001. When the device is found, it
will continue to parse the corresponding resources.
        For example:
		interface type (KCS, BT, SMIC) (SSIF is not supported)
		interrupt number and type (_GPE or GSI)
		Memory or IO base address
    2. register the IPMI system interface.

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
---
 drivers/char/ipmi/ipmi_si_intf.c |  394 ++++++++++++++++++++++++++++++++++++++
 1 files changed, 394 insertions(+), 0 deletions(-)

On Monday 26 October 2009 07:33:45 am yakui.zhao@intel.com wrote:
> From: Zhao Yakui <yakui.zhao@intel.com>
> 
> According to the IPMI 2.0 spec the IPMI system interface can be located with
> ACPI. One is located in SPMI table(Service Processor Management Interface
> table). Another is located in ACPI namespace.
> This patch is to locate the IPMI system interface in ACPI namespace and
> register it.
> It includes the following two steps:
>    1. enumerate the ACPI device tree to find the IPMI system interface
> 	The IPMI device type is IPI0001. When the device is found, it
> will continue to parse the corresponding resources.
>         For example:
> 		interface type (KCS, BT, SMIC) (SSIF is not supported)
> 		interrupt number and type (_GPE or GSI)
> 		Memory or IO base address
>     2. register the IPMI system interface.

As far as I can tell, these patches are unchanged from the original
ones you posted here:
  http://marc.info/?l=linux-acpi&m=125420227326811&w=2
  http://marc.info/?l=linux-acpi&m=125420227426814&w=2

Either you mistakenly posted the original patches again, or you
didn't address a single piece of the feedback we gave you.

Please don't waste my time asking for comments if you're just going
to ignore them.

It's OK if you think my suggestions are incorrect, but I expect you
to at least acknowledge them and explain why you disagree with me, so
we can have a discussion about it.

Bjorn

> Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
> ---
>  drivers/char/ipmi/ipmi_si_intf.c |  394 ++++++++++++++++++++++++++++++++++++++
>  1 files changed, 394 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
> index d2e6980..94d14bc 100644
> --- a/drivers/char/ipmi/ipmi_si_intf.c
> +++ b/drivers/char/ipmi/ipmi_si_intf.c
> @@ -1813,6 +1813,35 @@ static __devinit void hardcode_find_bmc(void)
>   * are no more.
>   */
>  static int acpi_failure;
> +static LIST_HEAD(acpi_ipmi);
> +
> +struct acpi_device_ipmi {
> +	struct list_head link;
> +	u8 interfacetype;
> +	/*
> +	 * Bit 0 - SCI interrupt supported
> +	 * Bit 1 - I/O APIC/SAPIC
> +	 */
> +	u8	interrupttype;
> +	/*
> +	 * If bit 0 of InterruptType is set, then this is the SCI
> +	 * interrupt in the GPEx_STS register.
> +	 */
> +	u8	gpe;
> +	/*
> +	 * If bit 1 of InterruptType is set, then this is the I/O
> +	 * APIC/SAPIC interrupt.
> +	 */
> +	u32	global_interrupt;
> +
> +	/* The actual register address. */
> +	struct acpi_generic_address addr;
> +	struct acpi_generic_address sm_addr;
> +
> +	u16 ipmi_revision;
> +	u8 resource_count;
> +	struct device *dev;
> +};
>  
>  /* For GPE-type interrupts. */
>  static u32 ipmi_acpi_gpe(void *context)
> @@ -2002,6 +2031,367 @@ static __devinit int try_init_acpi(struct SPMITable *spmi)
>  	return 0;
>  }
>  
> +static __devinit int try_init_acpi_device(struct acpi_device_ipmi *spmi)
> +{
> +	struct smi_info  *info;
> +	u8 		 addr_space;
> +
> +	if (spmi->addr.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
> +		addr_space = IPMI_MEM_ADDR_SPACE;
> +	else
> +		addr_space = IPMI_IO_ADDR_SPACE;
> +
> +	info = kzalloc(sizeof(*info), GFP_KERNEL);
> +	if (!info) {
> +		printk(KERN_ERR "ipmi_si: Could not allocate SI data (3)\n");
> +		return -ENOMEM;
> +	}
> +
> +	info->addr_source = "ACPI";
> +
> +	/* Figure out the interface type. */
> +	switch (spmi->interfacetype) {
> +	case 1:	/* KCS */
> +		info->si_type = SI_KCS;
> +		break;
> +	case 2:	/* SMIC */
> +		info->si_type = SI_SMIC;
> +		break;
> +	case 3:	/* BT */
> +		info->si_type = SI_BT;
> +		break;
> +	default:
> +		printk(KERN_INFO "ipmi_si: Unknown ACPI/SPMI SI type %d\n",
> +			spmi->interfacetype);
> +		kfree(info);
> +		return -EIO;
> +	}
> +
> +	if (spmi->interrupttype & 1) {
> +		/* We've got a GPE interrupt. */
> +		info->irq = spmi->gpe;
> +		info->irq_setup = acpi_gpe_irq_setup;
> +	} else if (spmi->interrupttype & 2) {
> +		/* We've got an APIC/SAPIC interrupt. */
> +		info->irq = spmi->global_interrupt;
> +		info->irq_setup = std_irq_setup;
> +	} else {
> +		/* Use the default interrupt setting. */
> +		info->irq = 0;
> +		info->irq_setup = NULL;
> +	}
> +
> +	if (spmi->addr.bit_width) {
> +		/* A (hopefully) properly formed register bit width. */
> +		info->io.regspacing = spmi->addr.bit_width / 8;
> +	} else {
> +		info->io.regspacing = DEFAULT_REGSPACING;
> +	}
> +	info->io.regsize = info->io.regspacing;
> +	info->io.regshift = spmi->addr.bit_offset;
> +
> +	if (spmi->addr.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
> +		info->io_setup = mem_setup;
> +		info->io.addr_type = IPMI_MEM_ADDR_SPACE;
> +	} else if (spmi->addr.space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
> +		info->io_setup = port_setup;
> +		info->io.addr_type = IPMI_IO_ADDR_SPACE;
> +	} else {
> +		kfree(info);
> +		printk(KERN_WARNING
> +		       "ipmi_si: Unknown ACPI I/O Address type\n");
> +		return -EIO;
> +	}
> +	info->io.addr_data = spmi->addr.address;
> +	info->dev = spmi->dev;
> +
> +	try_smi_init(info);
> +
> +	return 0;
> +}
> +
> +static acpi_status
> +acpi_parse_io_ports(struct acpi_resource *resource, void *context)
> +{
> +	struct acpi_device_ipmi *p_ipmi = context;
> +
> +	if (resource->type == ACPI_RESOURCE_TYPE_EXTENDED_IRQ ||
> +		resource->type == ACPI_RESOURCE_TYPE_IRQ) {
> +		unsigned int irq_number;
> +		if (p_ipmi->interrupttype) {
> +			/*
> +			 * If it already support the interrupt through GPE,
> +			 * it is unnecessary to get this interrupt again.
> +			 */
> +			printk(KERN_WARNING "Interrupt through GPE is already"
> +				" supported.\n");
> +			return AE_OK;
> +		}
> +		if (resource->type == ACPI_RESOURCE_TYPE_IRQ) {
> +			struct acpi_resource_irq *irq;
> +			irq = &resource->data.irq;
> +			if (irq->interrupt_count != 1) {
> +				printk(KERN_WARNING "incorrect IRQ is "
> +					"defined in _CRS\n");
> +				return AE_OK;
> +			}
> +			irq_number = irq->interrupts[0];
> +		} else {
> +			struct acpi_resource_extended_irq *extended_irq;
> +			extended_irq = &resource->data.extended_irq;
> +			if (extended_irq->interrupt_count != 1) {
> +				printk(KERN_WARNING "incorrect IRQ is "
> +					"defined in _CRS\n");
> +				return AE_OK;
> +			}
> +			irq_number = extended_irq->interrupts[0];
> +		}
> +		p_ipmi->global_interrupt = irq_number;
> +		if (p_ipmi->global_interrupt) {
> +			/* GSI interrupt type */
> +			p_ipmi->interrupttype |= 0x02;
> +		}
> +		return AE_OK;
> +	}
> +	if (resource->type == ACPI_RESOURCE_TYPE_IO ||
> +		resource->type == ACPI_RESOURCE_TYPE_FIXED_IO) {
> +		u16 address;
> +		struct acpi_resource_io *io;
> +		struct acpi_resource_fixed_io *fixed_io;
> +
> +		fixed_io = &resource->data.fixed_io;
> +		if (p_ipmi->resource_count) {
> +			/*
> +			 * Multiply definitions of IO/memory address are
> +			 * obtained. It is incorrect. We will continue
> +			 * to use the first IO/memory definition.
> +			 * If not correct, please fix me.
> +			 */
> +			return AE_OK;
> +		}
> +		if (resource->type == ACPI_RESOURCE_TYPE_IO) {
> +			io = &resource->data.io;
> +			if (!io->minimum) {
> +				/* when IO address is zero, return */
> +				return AE_OK;
> +			}
> +			address = io->minimum;
> +		} else {
> +			fixed_io = &resource->data.fixed_io;
> +			if (!fixed_io->address)
> +				return AE_OK;
> +			address = fixed_io->address;
> +		}
> +		p_ipmi->resource_count++;
> +		p_ipmi->addr.space_id = ACPI_ADR_SPACE_SYSTEM_IO;
> +		p_ipmi->addr.address = address;
> +		return AE_OK;
> +	}
> +
> +	if (resource->type == ACPI_RESOURCE_TYPE_MEMORY32 ||
> +		resource->type == ACPI_RESOURCE_TYPE_MEMORY24 ||
> +		resource->type == ACPI_RESOURCE_TYPE_FIXED_MEMORY32) {
> +		u32 address;
> +		if (p_ipmi->resource_count) {
> +			/*
> +			 * Multiply definitions of IO/memory address are
> +			 * obtained. It is incorrect. We will continue
> +			 * to use the first IO/memory definition.
> +			 * If not correct, please fix me.
> +			 */
> +			return AE_OK;
> +		}
> +		if (resource->type == ACPI_RESOURCE_TYPE_MEMORY32) {
> +			struct acpi_resource_memory32 *memory32;
> +			memory32 = &resource->data.memory32;
> +			address = memory32->minimum;
> +		} else if (resource->type == ACPI_RESOURCE_TYPE_MEMORY24) {
> +			struct acpi_resource_memory24 *memory24;
> +			memory24 = &resource->data.memory24;
> +			address = memory24->minimum;
> +		} else {
> +			struct acpi_resource_fixed_memory32 *fixed_memory32;
> +			fixed_memory32 = &resource->data.fixed_memory32;
> +			address = fixed_memory32->address;
> +		}
> +		p_ipmi->resource_count++;
> +		p_ipmi->addr.address = (u64) address;
> +		p_ipmi->addr.space_id = ACPI_ADR_SPACE_SYSTEM_MEMORY;
> +		return AE_OK;
> +	}
> +	if (resource->type == ACPI_RESOURCE_TYPE_ADDRESS16 ||
> +		resource->type == ACPI_RESOURCE_TYPE_ADDRESS32 ||
> +		resource->type == ACPI_RESOURCE_TYPE_ADDRESS64) {
> +		struct acpi_resource_address64 address64;
> +		acpi_resource_to_address64(resource, &address64);
> +		if (p_ipmi->resource_count) {
> +			/*
> +			 * Multiply definitions of IO/memory address are
> +			 * obtained. It is incorrect. We will continue
> +			 * to use the first IO/memory definition.
> +			 * If not correct, please fix me.
> +			 */
> +			return AE_OK;
> +		}
> +		if (address64.resource_type != ACPI_MEMORY_RANGE &&
> +			address64.resource_type != ACPI_IO_RANGE) {
> +			/* ignore the incorrect resource type */
> +			return AE_OK;
> +		}
> +		p_ipmi->addr.address = address64.minimum;
> +		p_ipmi->resource_count++;
> +		if (address64.resource_type == ACPI_MEMORY_RANGE)
> +			p_ipmi->addr.space_id = ACPI_ADR_SPACE_SYSTEM_MEMORY;
> +		else
> +			p_ipmi->addr.space_id = ACPI_ADR_SPACE_SYSTEM_IO;
> +
> +		return AE_OK;
> +	}
> +
> +	return AE_OK;
> +}
> +
> +/*
> + *  acpi_parse_bmc_resource -- parse the BMC resources from ACPI
> + *  @p_ipmi: the memory to store the BCM resource
> + *  @handle: ACPI device handle
> + */
> +static int acpi_parse_bmc_resource(struct acpi_device_ipmi *p_ipmi,
> +			acpi_handle handle)
> +{
> +	int parse_ok = false;
> +	unsigned long long	temp_data;
> +	acpi_status status;
> +
> +	/* According to IPMI spec there should exist the _IFT method
> +	 * for the IPMI device. So when there is no _IFT, it is regarded
> +	 * as the incorrect BMC device and won't parse the resource again.
> +	 */
> +	status = acpi_evaluate_integer(handle, "_IFT", NULL, &temp_data);
> +	if (ACPI_FAILURE(status))
> +		return parse_ok;
> +
> +	p_ipmi->interfacetype = temp_data;
> +	/* Figure out the interface type. If the interface type is not
> +	 * KCS/SMIC/BT, it is regared as the incorrect IPMI device.
> +	 * Of course the SSIF interface type is also defined, but we
> +	 * can't handle it. So it is not supported */
> +	switch (temp_data) {
> +	case 1:	/* KCS */
> +	case 2:	/* SMIC */
> +	case 3:	/* BT */
> +		break;
> +	default:
> +		printk(KERN_INFO "ipmi_si: Unknown ACPI/SPMI SI type %d\n",
> +			p_ipmi->interfacetype);
> +		return parse_ok;
> +	}
> +	/* check whether there exists the _GPE method. If it exists, it
> +	 * means that interrupt through GPE is supported.
> +	 */
> +	temp_data = 0;
> +	status = acpi_evaluate_integer(handle, "_GPE", NULL, &temp_data);
> +	if (ACPI_SUCCESS(status)) {
> +		p_ipmi->gpe = temp_data;
> +		/* set the GPE interrupt type */
> +		p_ipmi->interrupttype |= 0x01;
> +	}
> +	/* get the IPMI revision */
> +	temp_data = 0;
> +	status = acpi_evaluate_integer(handle, "_SRV", NULL,  &temp_data);
> +	if (ACPI_SUCCESS(status))
> +		p_ipmi->ipmi_revision = temp_data;
> +
> +	status = acpi_walk_resources(handle, METHOD_NAME__CRS,
> +				acpi_parse_io_ports, p_ipmi);
> +	if (ACPI_FAILURE(status)) {
> +		printk(KERN_WARNING "Can't parse the _CRS object \n");
> +		return parse_ok;
> +	}
> +	if (!p_ipmi->resource_count) {
> +		/* The incorrect IO/Memory address is parsed */
> +		printk(KERN_ERR "Incorrect IO/Memory address is parsed\n");
> +		return parse_ok;
> +	}
> +	parse_ok = true;
> +
> +	return parse_ok;
> +}
> +
> +const struct acpi_device_id ipmi_ids[] = {
> +	{"IPI0001", 0},
> +	{"", 0},
> +};
> +
> +/*
> + * acpi_check_bmc_device -- check whether @handle is a BMC device and then
> + *		get its corresponding resource. For example: IO/Mem
> + *		address, interface type
> + * @handle: ACPI device handle
> + * @level : depth in the ACPI namespace tree
> + * @context: the number of bmc device. In theory there is not more than
> + * 	one ACPI BMC device.
> + * @rv: a return value to fill if desired (Not use)
> + */
> +static acpi_status
> +acpi_check_bmc_device(acpi_handle handle, u32 level, void *context,
> +			void **return_value)
> +{
> +	struct acpi_device *acpi_dev;
> +	struct acpi_device_ipmi *p_ipmi = NULL;
> +	int *count = (int *)context;
> +
> +	acpi_dev = NULL;
> +	/* Get the acpi device for device handle */
> +	if (acpi_bus_get_device(handle, &acpi_dev) || !acpi_dev) {
> +		/* If there is no ACPI device for handle, return */
> +		return AE_OK;
> +	}
> +
> +	if (acpi_match_device_ids(acpi_dev, ipmi_ids))
> +		return AE_OK;
> +
> +	p_ipmi = kzalloc(sizeof(*p_ipmi), GFP_KERNEL);
> +	if (!p_ipmi) {
> +		printk(KERN_ERR "Can't allocate memory for IPMI device\n");
> +		return AE_OK;
> +	}
> +	p_ipmi->dev = &acpi_dev->dev;
> +	if (!acpi_parse_bmc_resource(p_ipmi, handle)) {
> +		kfree(p_ipmi);
> +	} else {
> +		list_add_tail(&p_ipmi->link, &acpi_ipmi);
> +		*count = *count + 1;
> +	}
> +
> +	return AE_OK;
> +}
> +
> +static __devinit void acpi_device_find_bmc(void)
> +{
> +	acpi_status      status;
> +	int              device_count = 0;
> +	struct acpi_device_ipmi *p_ipmi, *p_ipmi2;
> +
> +	if (acpi_disabled)
> +		return;
> +
> +	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
> +				ACPI_UINT32_MAX,
> +				acpi_check_bmc_device, &device_count, NULL);
> +	if (!device_count) {
> +		/* when no IPMI device is found in ACPI namespace, return */
> +		return;
> +	}
> +	list_for_each_entry_safe(p_ipmi, p_ipmi2, &acpi_ipmi, link) {
> +		try_init_acpi_device(p_ipmi);
> +		list_del(&p_ipmi->link);
> +		kfree(p_ipmi);
> +	}
> +
> +	return;
> +}
> +
>  static __devinit void acpi_find_bmc(void)
>  {
>  	acpi_status      status;
> @@ -2014,6 +2404,7 @@ static __devinit void acpi_find_bmc(void)
>  	if (acpi_failure)
>  		return;
>  
> +	/* locate the IPMI system interface in ACPI SPMI table */
>  	for (i = 0; ; i++) {
>  		status = acpi_get_table(ACPI_SIG_SPMI, i+1,
>  					(struct acpi_table_header **)&spmi);
> @@ -2022,6 +2413,9 @@ static __devinit void acpi_find_bmc(void)
>  
>  		try_init_acpi(spmi);
>  	}
> +
> +	/* locate the IPMI system interface in ACPI device */
> +	acpi_device_find_bmc();
>  }
>  #endif
>  


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On Mon, 2009-10-26 at 23:20 +0800, Bjorn Helgaas wrote:
> On Monday 26 October 2009 07:33:45 am yakui.zhao@intel.com wrote:
> > From: Zhao Yakui <yakui.zhao@intel.com>
> >
> > According to the IPMI 2.0 spec the IPMI system interface can be located with
> > ACPI. One is located in SPMI table(Service Processor Management Interface
> > table). Another is located in ACPI namespace.
> > This patch is to locate the IPMI system interface in ACPI namespace and
> > register it.
> > It includes the following two steps:
> >    1. enumerate the ACPI device tree to find the IPMI system interface
> >       The IPMI device type is IPI0001. When the device is found, it
> > will continue to parse the corresponding resources.
> >         For example:
> >               interface type (KCS, BT, SMIC) (SSIF is not supported)
> >               interrupt number and type (_GPE or GSI)
> >               Memory or IO base address
> >     2. register the IPMI system interface

> As far as I can tell, these patches are unchanged from the original
> ones you posted here:
>   http://marc.info/?l=linux-acpi&m=125420227326811&w=2
>   http://marc.info/?l=linux-acpi&m=125420227426814&w=2
I refresh them based on the latest upstream branch. Of course I do the
small change about the second patch. It is mainly about the coding
style.

In fact you mention two issues about the two patches:
   1: Load a PNP driver for it to register the IPMI system interface.
This is about the first patch.
   2. coding style( for example: comments, the definition about some
variables).

For the first issue: Before I start the first patch, I consider using
the PNP device driver. But I find that it is so complex because of the
following two points:
    1. One is that we can't register the IPMI system interface if the
boot option of "pnpacpi=off" is added. This will also depend on the PNP
module.
    2. The second is that there exist so many cases about the IPMI
IO/memory resource definition. Maybe there exist both IO/memory resource
definition for one IPMI device. In such case we can't know which should
be selected. At the same time we have similar issues about the interrupt
type. So I decide to parse the IO/memory/interrupt resource
independently.
Very sorry that I don't reply the above points in the discussion.

For the second patch: 
   I update the coding style about the comments. But I don't change the
coding style about the variable definition as it doesn't matter. At the
same time it is easy to understand by using the explicit definition.
   For example: 
      if (acpi_disabled)
               return;

thanks.
   yakui

> Either you mistakenly posted the original patches again, or you
> didn't address a single piece of the feedback we gave you.
> 
> Please don't waste my time asking for comments if you're just going
> to ignore them.
> 
> It's OK if you think my suggestions are incorrect, but I expect you
> to at least acknowledge them and explain why you disagree with me, so
> we can have a discussion about it.
> 
> Bjorn
> 
> > Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
> > ---
> >  drivers/char/ipmi/ipmi_si_intf.c |  394 ++++++++++++++++++++++++++++++++++++++
> >  1 files changed, 394 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
> > index d2e6980..94d14bc 100644
> > --- a/drivers/char/ipmi/ipmi_si_intf.c
> > +++ b/drivers/char/ipmi/ipmi_si_intf.c
> > @@ -1813,6 +1813,35 @@ static __devinit void hardcode_find_bmc(void)
> >   * are no more.
> >   */
> >  static int acpi_failure;
> > +static LIST_HEAD(acpi_ipmi);
> > +
> > +struct acpi_device_ipmi {
> > +     struct list_head link;
> > +     u8 interfacetype;
> > +     /*
> > +      * Bit 0 - SCI interrupt supported
> > +      * Bit 1 - I/O APIC/SAPIC
> > +      */
> > +     u8      interrupttype;
> > +     /*
> > +      * If bit 0 of InterruptType is set, then this is the SCI
> > +      * interrupt in the GPEx_STS register.
> > +      */
> > +     u8      gpe;
> > +     /*
> > +      * If bit 1 of InterruptType is set, then this is the I/O
> > +      * APIC/SAPIC interrupt.
> > +      */
> > +     u32     global_interrupt;
> > +
> > +     /* The actual register address. */
> > +     struct acpi_generic_address addr;
> > +     struct acpi_generic_address sm_addr;
> > +
> > +     u16 ipmi_revision;
> > +     u8 resource_count;
> > +     struct device *dev;
> > +};
> >
> >  /* For GPE-type interrupts. */
> >  static u32 ipmi_acpi_gpe(void *context)
> > @@ -2002,6 +2031,367 @@ static __devinit int try_init_acpi(struct SPMITable *spmi)
> >       return 0;
> >  }
> >
> > +static __devinit int try_init_acpi_device(struct acpi_device_ipmi *spmi)
> > +{
> > +     struct smi_info  *info;
> > +     u8               addr_space;
> > +
> > +     if (spmi->addr.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY)
> > +             addr_space = IPMI_MEM_ADDR_SPACE;
> > +     else
> > +             addr_space = IPMI_IO_ADDR_SPACE;
> > +
> > +     info = kzalloc(sizeof(*info), GFP_KERNEL);
> > +     if (!info) {
> > +             printk(KERN_ERR "ipmi_si: Could not allocate SI data (3)\n");
> > +             return -ENOMEM;
> > +     }
> > +
> > +     info->addr_source = "ACPI";
> > +
> > +     /* Figure out the interface type. */
> > +     switch (spmi->interfacetype) {
> > +     case 1: /* KCS */
> > +             info->si_type = SI_KCS;
> > +             break;
> > +     case 2: /* SMIC */
> > +             info->si_type = SI_SMIC;
> > +             break;
> > +     case 3: /* BT */
> > +             info->si_type = SI_BT;
> > +             break;
> > +     default:
> > +             printk(KERN_INFO "ipmi_si: Unknown ACPI/SPMI SI type %d\n",
> > +                     spmi->interfacetype);
> > +             kfree(info);
> > +             return -EIO;
> > +     }
> > +
> > +     if (spmi->interrupttype & 1) {
> > +             /* We've got a GPE interrupt. */
> > +             info->irq = spmi->gpe;
> > +             info->irq_setup = acpi_gpe_irq_setup;
> > +     } else if (spmi->interrupttype & 2) {
> > +             /* We've got an APIC/SAPIC interrupt. */
> > +             info->irq = spmi->global_interrupt;
> > +             info->irq_setup = std_irq_setup;
> > +     } else {
> > +             /* Use the default interrupt setting. */
> > +             info->irq = 0;
> > +             info->irq_setup = NULL;
> > +     }
> > +
> > +     if (spmi->addr.bit_width) {
> > +             /* A (hopefully) properly formed register bit width. */
> > +             info->io.regspacing = spmi->addr.bit_width / 8;
> > +     } else {
> > +             info->io.regspacing = DEFAULT_REGSPACING;
> > +     }
> > +     info->io.regsize = info->io.regspacing;
> > +     info->io.regshift = spmi->addr.bit_offset;
> > +
> > +     if (spmi->addr.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY) {
> > +             info->io_setup = mem_setup;
> > +             info->io.addr_type = IPMI_MEM_ADDR_SPACE;
> > +     } else if (spmi->addr.space_id == ACPI_ADR_SPACE_SYSTEM_IO) {
> > +             info->io_setup = port_setup;
> > +             info->io.addr_type = IPMI_IO_ADDR_SPACE;
> > +     } else {
> > +             kfree(info);
> > +             printk(KERN_WARNING
> > +                    "ipmi_si: Unknown ACPI I/O Address type\n");
> > +             return -EIO;
> > +     }
> > +     info->io.addr_data = spmi->addr.address;
> > +     info->dev = spmi->dev;
> > +
> > +     try_smi_init(info);
> > +
> > +     return 0;
> > +}
> > +
> > +static acpi_status
> > +acpi_parse_io_ports(struct acpi_resource *resource, void *context)
> > +{
> > +     struct acpi_device_ipmi *p_ipmi = context;
> > +
> > +     if (resource->type == ACPI_RESOURCE_TYPE_EXTENDED_IRQ ||
> > +             resource->type == ACPI_RESOURCE_TYPE_IRQ) {
> > +             unsigned int irq_number;
> > +             if (p_ipmi->interrupttype) {
> > +                     /*
> > +                      * If it already support the interrupt through GPE,
> > +                      * it is unnecessary to get this interrupt again.
> > +                      */
> > +                     printk(KERN_WARNING "Interrupt through GPE is already"
> > +                             " supported.\n");
> > +                     return AE_OK;
> > +             }
> > +             if (resource->type == ACPI_RESOURCE_TYPE_IRQ) {
> > +                     struct acpi_resource_irq *irq;
> > +                     irq = &resource->data.irq;
> > +                     if (irq->interrupt_count != 1) {
> > +                             printk(KERN_WARNING "incorrect IRQ is "
> > +                                     "defined in _CRS\n");
> > +                             return AE_OK;
> > +                     }
> > +                     irq_number = irq->interrupts[0];
> > +             } else {
> > +                     struct acpi_resource_extended_irq *extended_irq;
> > +                     extended_irq = &resource->data.extended_irq;
> > +                     if (extended_irq->interrupt_count != 1) {
> > +                             printk(KERN_WARNING "incorrect IRQ is "
> > +                                     "defined in _CRS\n");
> > +                             return AE_OK;
> > +                     }
> > +                     irq_number = extended_irq->interrupts[0];
> > +             }
> > +             p_ipmi->global_interrupt = irq_number;
> > +             if (p_ipmi->global_interrupt) {
> > +                     /* GSI interrupt type */
> > +                     p_ipmi->interrupttype |= 0x02;
> > +             }
> > +             return AE_OK;
> > +     }
> > +     if (resource->type == ACPI_RESOURCE_TYPE_IO ||
> > +             resource->type == ACPI_RESOURCE_TYPE_FIXED_IO) {
> > +             u16 address;
> > +             struct acpi_resource_io *io;
> > +             struct acpi_resource_fixed_io *fixed_io;
> > +
> > +             fixed_io = &resource->data.fixed_io;
> > +             if (p_ipmi->resource_count) {
> > +                     /*
> > +                      * Multiply definitions of IO/memory address are
> > +                      * obtained. It is incorrect. We will continue
> > +                      * to use the first IO/memory definition.
> > +                      * If not correct, please fix me.
> > +                      */
> > +                     return AE_OK;
> > +             }
> > +             if (resource->type == ACPI_RESOURCE_TYPE_IO) {
> > +                     io = &resource->data.io;
> > +                     if (!io->minimum) {
> > +                             /* when IO address is zero, return */
> > +                             return AE_OK;
> > +                     }
> > +                     address = io->minimum;
> > +             } else {
> > +                     fixed_io = &resource->data.fixed_io;
> > +                     if (!fixed_io->address)
> > +                             return AE_OK;
> > +                     address = fixed_io->address;
> > +             }
> > +             p_ipmi->resource_count++;
> > +             p_ipmi->addr.space_id = ACPI_ADR_SPACE_SYSTEM_IO;
> > +             p_ipmi->addr.address = address;
> > +             return AE_OK;
> > +     }
> > +
> > +     if (resource->type == ACPI_RESOURCE_TYPE_MEMORY32 ||
> > +             resource->type == ACPI_RESOURCE_TYPE_MEMORY24 ||
> > +             resource->type == ACPI_RESOURCE_TYPE_FIXED_MEMORY32) {
> > +             u32 address;
> > +             if (p_ipmi->resource_count) {
> > +                     /*
> > +                      * Multiply definitions of IO/memory address are
> > +                      * obtained. It is incorrect. We will continue
> > +                      * to use the first IO/memory definition.
> > +                      * If not correct, please fix me.
> > +                      */
> > +                     return AE_OK;
> > +             }
> > +             if (resource->type == ACPI_RESOURCE_TYPE_MEMORY32) {
> > +                     struct acpi_resource_memory32 *memory32;
> > +                     memory32 = &resource->data.memory32;
> > +                     address = memory32->minimum;
> > +             } else if (resource->type == ACPI_RESOURCE_TYPE_MEMORY24) {
> > +                     struct acpi_resource_memory24 *memory24;
> > +                     memory24 = &resource->data.memory24;
> > +                     address = memory24->minimum;
> > +             } else {
> > +                     struct acpi_resource_fixed_memory32 *fixed_memory32;
> > +                     fixed_memory32 = &resource->data.fixed_memory32;
> > +                     address = fixed_memory32->address;
> > +             }
> > +             p_ipmi->resource_count++;
> > +             p_ipmi->addr.address = (u64) address;
> > +             p_ipmi->addr.space_id = ACPI_ADR_SPACE_SYSTEM_MEMORY;
> > +             return AE_OK;
> > +     }
> > +     if (resource->type == ACPI_RESOURCE_TYPE_ADDRESS16 ||
> > +             resource->type == ACPI_RESOURCE_TYPE_ADDRESS32 ||
> > +             resource->type == ACPI_RESOURCE_TYPE_ADDRESS64) {
> > +             struct acpi_resource_address64 address64;
> > +             acpi_resource_to_address64(resource, &address64);
> > +             if (p_ipmi->resource_count) {
> > +                     /*
> > +                      * Multiply definitions of IO/memory address are
> > +                      * obtained. It is incorrect. We will continue
> > +                      * to use the first IO/memory definition.
> > +                      * If not correct, please fix me.
> > +                      */
> > +                     return AE_OK;
> > +             }
> > +             if (address64.resource_type != ACPI_MEMORY_RANGE &&
> > +                     address64.resource_type != ACPI_IO_RANGE) {
> > +                     /* ignore the incorrect resource type */
> > +                     return AE_OK;
> > +             }
> > +             p_ipmi->addr.address = address64.minimum;
> > +             p_ipmi->resource_count++;
> > +             if (address64.resource_type == ACPI_MEMORY_RANGE)
> > +                     p_ipmi->addr.space_id = ACPI_ADR_SPACE_SYSTEM_MEMORY;
> > +             else
> > +                     p_ipmi->addr.space_id = ACPI_ADR_SPACE_SYSTEM_IO;
> > +
> > +             return AE_OK;
> > +     }
> > +
> > +     return AE_OK;
> > +}
> > +
> > +/*
> > + *  acpi_parse_bmc_resource -- parse the BMC resources from ACPI
> > + *  @p_ipmi: the memory to store the BCM resource
> > + *  @handle: ACPI device handle
> > + */
> > +static int acpi_parse_bmc_resource(struct acpi_device_ipmi *p_ipmi,
> > +                     acpi_handle handle)
> > +{
> > +     int parse_ok = false;
> > +     unsigned long long      temp_data;
> > +     acpi_status status;
> > +
> > +     /* According to IPMI spec there should exist the _IFT method
> > +      * for the IPMI device. So when there is no _IFT, it is regarded
> > +      * as the incorrect BMC device and won't parse the resource again.
> > +      */
> > +     status = acpi_evaluate_integer(handle, "_IFT", NULL, &temp_data);
> > +     if (ACPI_FAILURE(status))
> > +             return parse_ok;
> > +
> > +     p_ipmi->interfacetype = temp_data;
> > +     /* Figure out the interface type. If the interface type is not
> > +      * KCS/SMIC/BT, it is regared as the incorrect IPMI device.
> > +      * Of course the SSIF interface type is also defined, but we
> > +      * can't handle it. So it is not supported */
> > +     switch (temp_data) {
> > +     case 1: /* KCS */
> > +     case 2: /* SMIC */
> > +     case 3: /* BT */
> > +             break;
> > +     default:
> > +             printk(KERN_INFO "ipmi_si: Unknown ACPI/SPMI SI type %d\n",
> > +                     p_ipmi->interfacetype);
> > +             return parse_ok;
> > +     }
> > +     /* check whether there exists the _GPE method. If it exists, it
> > +      * means that interrupt through GPE is supported.
> > +      */
> > +     temp_data = 0;
> > +     status = acpi_evaluate_integer(handle, "_GPE", NULL, &temp_data);
> > +     if (ACPI_SUCCESS(status)) {
> > +             p_ipmi->gpe = temp_data;
> > +             /* set the GPE interrupt type */
> > +             p_ipmi->interrupttype |= 0x01;
> > +     }
> > +     /* get the IPMI revision */
> > +     temp_data = 0;
> > +     status = acpi_evaluate_integer(handle, "_SRV", NULL,  &temp_data);
> > +     if (ACPI_SUCCESS(status))
> > +             p_ipmi->ipmi_revision = temp_data;
> > +
> > +     status = acpi_walk_resources(handle, METHOD_NAME__CRS,
> > +                             acpi_parse_io_ports, p_ipmi);
> > +     if (ACPI_FAILURE(status)) {
> > +             printk(KERN_WARNING "Can't parse the _CRS object \n");
> > +             return parse_ok;
> > +     }
> > +     if (!p_ipmi->resource_count) {
> > +             /* The incorrect IO/Memory address is parsed */
> > +             printk(KERN_ERR "Incorrect IO/Memory address is parsed\n");
> > +             return parse_ok;
> > +     }
> > +     parse_ok = true;
> > +
> > +     return parse_ok;
> > +}
> > +
> > +const struct acpi_device_id ipmi_ids[] = {
> > +     {"IPI0001", 0},
> > +     {"", 0},
> > +};
> > +
> > +/*
> > + * acpi_check_bmc_device -- check whether @handle is a BMC device and then
> > + *           get its corresponding resource. For example: IO/Mem
> > + *           address, interface type
> > + * @handle: ACPI device handle
> > + * @level : depth in the ACPI namespace tree
> > + * @context: the number of bmc device. In theory there is not more than
> > + *   one ACPI BMC device.
> > + * @rv: a return value to fill if desired (Not use)
> > + */
> > +static acpi_status
> > +acpi_check_bmc_device(acpi_handle handle, u32 level, void *context,
> > +                     void **return_value)
> > +{
> > +     struct acpi_device *acpi_dev;
> > +     struct acpi_device_ipmi *p_ipmi = NULL;
> > +     int *count = (int *)context;
> > +
> > +     acpi_dev = NULL;
> > +     /* Get the acpi device for device handle */
> > +     if (acpi_bus_get_device(handle, &acpi_dev) || !acpi_dev) {
> > +             /* If there is no ACPI device for handle, return */
> > +             return AE_OK;
> > +     }
> > +
> > +     if (acpi_match_device_ids(acpi_dev, ipmi_ids))
> > +             return AE_OK;
> > +
> > +     p_ipmi = kzalloc(sizeof(*p_ipmi), GFP_KERNEL);
> > +     if (!p_ipmi) {
> > +             printk(KERN_ERR "Can't allocate memory for IPMI device\n");
> > +             return AE_OK;
> > +     }
> > +     p_ipmi->dev = &acpi_dev->dev;
> > +     if (!acpi_parse_bmc_resource(p_ipmi, handle)) {
> > +             kfree(p_ipmi);
> > +     } else {
> > +             list_add_tail(&p_ipmi->link, &acpi_ipmi);
> > +             *count = *count + 1;
> > +     }
> > +
> > +     return AE_OK;
> > +}
> > +
> > +static __devinit void acpi_device_find_bmc(void)
> > +{
> > +     acpi_status      status;
> > +     int              device_count = 0;
> > +     struct acpi_device_ipmi *p_ipmi, *p_ipmi2;
> > +
> > +     if (acpi_disabled)
> > +             return;
> > +
> > +     status = acpi_walk_namespace(ACPI_TYPE_DEVICE, ACPI_ROOT_OBJECT,
> > +                             ACPI_UINT32_MAX,
> > +                             acpi_check_bmc_device, &device_count, NULL);
> > +     if (!device_count) {
> > +             /* when no IPMI device is found in ACPI namespace, return */
> > +             return;
> > +     }
> > +     list_for_each_entry_safe(p_ipmi, p_ipmi2, &acpi_ipmi, link) {
> > +             try_init_acpi_device(p_ipmi);
> > +             list_del(&p_ipmi->link);
> > +             kfree(p_ipmi);
> > +     }
> > +
> > +     return;
> > +}
> > +
> >  static __devinit void acpi_find_bmc(void)
> >  {
> >       acpi_status      status;
> > @@ -2014,6 +2404,7 @@ static __devinit void acpi_find_bmc(void)
> >       if (acpi_failure)
> >               return;
> >
> > +     /* locate the IPMI system interface in ACPI SPMI table */
> >       for (i = 0; ; i++) {
> >               status = acpi_get_table(ACPI_SIG_SPMI, i+1,
> >                                       (struct acpi_table_header **)&spmi);
> > @@ -2022,6 +2413,9 @@ static __devinit void acpi_find_bmc(void)
> >
> >               try_init_acpi(spmi);
> >       }
> > +
> > +     /* locate the IPMI system interface in ACPI device */
> > +     acpi_device_find_bmc();
> >  }
> >  #endif
> >
> 
> 

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On Monday 26 October 2009 07:02:55 pm ykzhao wrote:
> In fact you mention two issues about the two patches:
>    1: Load a PNP driver for it to register the IPMI system interface.
> This is about the first patch.
>    2. coding style( for example: comments, the definition about some
> variables).
> 
> For the first issue: Before I start the first patch, I consider using
> the PNP device driver. But I find that it is so complex because of the
> following two points:
>     1. One is that we can't register the IPMI system interface if the
> boot option of "pnpacpi=off" is added. This will also depend on the PNP
> module.

This is not a problem.  It is perfectly acceptable for the IPMI driver
to depend on PNP and PNPACPI in order to claim an ACPI device.  If the
users boots with "pnpacpi=off", we just won't find an IPMI device.
That is the way it works for TPM devices and serial devices described
by ACPI, and IPMI should work the same way.

>     2. The second is that there exist so many cases about the IPMI
> IO/memory resource definition. Maybe there exist both IO/memory resource
> definition for one IPMI device. In such case we can't know which should
> be selected. At the same time we have similar issues about the interrupt
> type. So I decide to parse the IO/memory/interrupt resource
> independently.

This doesn't make any sense.  The fact that an IPMI device might have
a variety of IO/memory/IRQ resources is orthogonal to the question of
whether you should use pnp_register_driver() or acpi_walk_namespace().

PNPACPI parses the IPMI device resources for every ACPI device,
including the IPMI device, before we even know whether there will be
a PNP driver for the device.  It's much easier to look at the PNP
resources and figure out which to use than it is to use
acpi_walk_resources() manually.

The main point is that ipmi_si_intf.c is a device driver, and it should
use the normal driver registration mechanisms.  I think it would be
simplest and clearest to make a few PNP enhancements so it could use
pnp_register_driver(), but even using acpi_bus_register_driver() would
be fine.  Using acpi_walk_namespace() to do everything by hand is just
completely wrong.

Bjorn


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On Tuesday 27 October 2009 09:38:41 am Bjorn Helgaas wrote:
> On Monday 26 October 2009 07:02:55 pm ykzhao wrote:
> > In fact you mention two issues about the two patches:
> >    1: Load a PNP driver for it to register the IPMI system interface.
> > This is about the first patch.
> >    2. coding style( for example: comments, the definition about some
> > variables).
> > 
> > For the first issue: Before I start the first patch, I consider using
> > the PNP device driver. But I find that it is so complex because of the
> > following two points:
> >     1. One is that we can't register the IPMI system interface if the
> > boot option of "pnpacpi=off" is added. This will also depend on the PNP
> > module.
> 
> This is not a problem.  It is perfectly acceptable for the IPMI driver
> to depend on PNP and PNPACPI in order to claim an ACPI device.  If the
> users boots with "pnpacpi=off", we just won't find an IPMI device.
> That is the way it works for TPM devices and serial devices described
> by ACPI, and IPMI should work the same way.
> 
> >     2. The second is that there exist so many cases about the IPMI
> > IO/memory resource definition. Maybe there exist both IO/memory resource
> > definition for one IPMI device. In such case we can't know which should
> > be selected. At the same time we have similar issues about the interrupt
> > type. So I decide to parse the IO/memory/interrupt resource
> > independently.
> 
> This doesn't make any sense.  The fact that an IPMI device might have
> a variety of IO/memory/IRQ resources is orthogonal to the question of
> whether you should use pnp_register_driver() or acpi_walk_namespace().
> 
> PNPACPI parses the IPMI device resources for every ACPI device,
> including the IPMI device, before we even know whether there will be
> a PNP driver for the device.  It's much easier to look at the PNP
> resources and figure out which to use than it is to use
> acpi_walk_resources() manually.
> 
> The main point is that ipmi_si_intf.c is a device driver, and it should
> use the normal driver registration mechanisms.  I think it would be
> simplest and clearest to make a few PNP enhancements so it could use
> pnp_register_driver(), but even using acpi_bus_register_driver() would
> be fine.  Using acpi_walk_namespace() to do everything by hand is just
> completely wrong.

Somebody asked me to clarify this, so here's some explanation that
might make this more clear.

He pointed out:
> The IPMI driver "stack" is split into three levels.  The middle
> layer, ipmi_msghandler, routes commands/responses/etc between
> upper and lower levels.  It has no clue about hardware OR device
> files.  It must be loaded first.
> 
> Lowest level is ipmi_si_intf, and talks directly to hardware, and
> it cares about memory/ports/IRQs/etc.  It only talks to ipmi_msghandler.
> Embedded in it are the three subdrivers (BT, KCS, SMIC) that
> do actual bit twiddling.
> 
> The top layer presents a character device file.  It connects only
> to ipmi_msghandler.
> 
> So device file registration stuff occurs in an entirely different
> source module than ACPI/PNP lookup.

I'm not concerned with the top or middle layers or the device file
registration.  The bottom layer talks directly to hardware, and that
makes it a Linux driver.  It has to use the right I/O ports, MMIO
regions, IRQs, etc., so it avoids conflicts with other devices in
the system.

The fact that your patch uses acpi_walk_namespace() to find the
device means that ipmi_si_intf.c can be talking to a device, but the
rest of the system doesn't know ipmi_si_intf.c "owns" it.  So another
driver B could come along and correctly use acpi_bus_register_driver()
with the IPMI IDs.  The Linux ACPI core knows nothing about the fact
that ipmi_si_intf.c thinks it "owns" the IPMI device, so it will call
the driver B "add" method.  Now we have two drivers that both think
they own the device.  This leads to chaos.

Bjorn
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Hi Bjorn,

Currently EC driver work by doing either ECDT parse or acpi_walk_namespace,
Do you think it will be appropriate to change it to use PNP layer?

Thanks in advance,
Alex.

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On Tuesday 27 October 2009 12:02:01 pm Alexey Starikovskiy wrote:
> Currently EC driver work by doing either ECDT parse or acpi_walk_namespace,
> Do you think it will be appropriate to change it to use PNP layer?

I don't see this.  In acpi_ec_init(), there's an acpi_bus_register_driver().
There's also the ECDT parsing in acpi_ec_ecdt_probe().  There's a comment
near the acpi_ec_ecdt_probe() call that says it must happen before the EC
is found in the namespace.

There is an acpi_walk_namespace() inside acpi_ec_add(), but that's only
to find _Qx methods under an EC device we've already found.

It's conceivable that the EC driver could use PNP registration rather
than ACPI registration -- that would let you get rid of the
acpi_walk_resources() in ec_parse_device().  But I don't know that
it's worth it right now.

For IPMI, we're adding a bunch of new code and there are structural
problems that EC doesn't have.  So IPMI feels more urgent to me.

Bjorn
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On Tue, 2009-10-27 at 23:38 +0800, Bjorn Helgaas wrote:
> On Monday 26 October 2009 07:02:55 pm ykzhao wrote:
> > In fact you mention two issues about the two patches:
> >    1: Load a PNP driver for it to register the IPMI system interface.
> > This is about the first patch.
> >    2. coding style( for example: comments, the definition about some
> > variables).
> > 
> > For the first issue: Before I start the first patch, I consider using
> > the PNP device driver. But I find that it is so complex because of the
> > following two points:
> >     1. One is that we can't register the IPMI system interface if the
> > boot option of "pnpacpi=off" is added. This will also depend on the PNP
> > module.
> 
> This is not a problem.  It is perfectly acceptable for the IPMI driver
> to depend on PNP and PNPACPI in order to claim an ACPI device.  If the
> users boots with "pnpacpi=off", we just won't find an IPMI device.
> That is the way it works for TPM devices and serial devices described
> by ACPI, and IPMI should work the same way.
Yes. Several methods can be used to detect the IPMI system interface.
In such case it still can be detected by using other method when the
ACPI detection mechanism is disabled. But the acpi detection mechanism
will depend on the ACPI and PNP subsystem if we detect the IMPI system
interface defined in ACPI table by using PNP device driver. 

At the same time there exist two ACPI detection mechanisms. One is
defined in SPMI table. The other is defined in ACPI table. We expect
that the two ACPI detection mechanisms depend on the same judgement
condition. 
So I prefer to detect the IPMI system interface when ACPI enabled
regardless of the boot option of "pnpacpi=off".
> 
> >     2. The second is that there exist so many cases about the IPMI
> > IO/memory resource definition. Maybe there exist both IO/memory resource
> > definition for one IPMI device. In such case we can't know which should
> > be selected. At the same time we have similar issues about the interrupt
> > type. So I decide to parse the IO/memory/interrupt resource
> > independently.
> 
> This doesn't make any sense.  The fact that an IPMI device might have
> a variety of IO/memory/IRQ resources is orthogonal to the question of
> whether you should use pnp_register_driver() or acpi_walk_namespace().
When we detect the IPMI system interface by loading PNP device driver,
the advantage is that it can re-use the parse mechanism of
IO/memory/interrupt. Right?
In fact we will have to evaluate the following ACPI object:
	>_IFT, _GPE, _SRV

If there exists the _GPE object, it is unnecessary to parse the resource
related with the interrupt.

At the same time as I mentioned in the previous email, sometimes we will
get the two different IO address definitions after evaluating the _CRS
object. Which should be selected?
If there exist both IO and memory address definition in _CRS object,
which should be selected?

> PNPACPI parses the IPMI device resources for every ACPI device,
> including the IPMI device, before we even know whether there will be
> a PNP driver for the device.  It's much easier to look at the PNP
> resources and figure out which to use than it is to use
> acpi_walk_resources() manually.
> 
> The main point is that ipmi_si_intf.c is a device driver, and it should
> use the normal driver registration mechanisms.  I think it would be
> simplest and clearest to make a few PNP enhancements so it could use
> pnp_register_driver(), but even using acpi_bus_register_driver() would
> be fine.  Using acpi_walk_namespace() to do everything by hand is just
> completely wrong.
The main purpose is to detect the IPMI system interface defined in ACPI
table.  If the device can be detected correctly, IMO it will be OK.

Why do think that it is wrong to use the acpi_walk_namespace to parse
the resource?

In the second patch it will register an ACPI device driver, which is
used to install the IPMI opregion space handler. After doing so, the
ACPI AML code can communicate with the IPMI system interface.

> 
> Bjorn
> 
> 

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On Wed, 2009-10-28 at 10:50 +0800, ykzhao wrote:
> On Tue, 2009-10-27 at 23:38 +0800, Bjorn Helgaas wrote:
> > On Monday 26 October 2009 07:02:55 pm ykzhao wrote:
> > > In fact you mention two issues about the two patches:
> > >    1: Load a PNP driver for it to register the IPMI system interface.
> > > This is about the first patch.
> > >    2. coding style( for example: comments, the definition about some
> > > variables).
> > > 
> > > For the first issue: Before I start the first patch, I consider using
> > > the PNP device driver. But I find that it is so complex because of the
> > > following two points:
> > >     1. One is that we can't register the IPMI system interface if the
> > > boot option of "pnpacpi=off" is added. This will also depend on the PNP
> > > module.
> > 
> > This is not a problem.  It is perfectly acceptable for the IPMI driver
> > to depend on PNP and PNPACPI in order to claim an ACPI device.  If the
> > users boots with "pnpacpi=off", we just won't find an IPMI device.
> > That is the way it works for TPM devices and serial devices described
> > by ACPI, and IPMI should work the same way.
> Yes. Several methods can be used to detect the IPMI system interface.
> In such case it still can be detected by using other method when the
> ACPI detection mechanism is disabled. But the acpi detection mechanism
> will depend on the ACPI and PNP subsystem if we detect the IMPI system
> interface defined in ACPI table by using PNP device driver. 
> 
> At the same time there exist two ACPI detection mechanisms. One is
> defined in SPMI table. The other is defined in ACPI table. We expect
> that the two ACPI detection mechanisms depend on the same judgement
> condition. 
> So I prefer to detect the IPMI system interface when ACPI enabled
> regardless of the boot option of "pnpacpi=off".

The IPMI driver is not special.  It should behave like all other
drivers.  There is no reason it should handle the "pnpacpi=off" case
differently than other drivers.

But if you change this to use acpi_bus_register_driver(), there will be
no PNP dependency, "pnpacpi=off" will have no effect either way, and
I'll be happy.  I don't think it's the cleanest solution, but it at
least gives us a chance to properly bind the driver to the device.

> > >     2. The second is that there exist so many cases about the IPMI
> > > IO/memory resource definition. Maybe there exist both IO/memory resource
> > > definition for one IPMI device. In such case we can't know which should
> > > be selected. At the same time we have similar issues about the interrupt
> > > type. So I decide to parse the IO/memory/interrupt resource
> > > independently.
> > 
> > This doesn't make any sense.  The fact that an IPMI device might have
> > a variety of IO/memory/IRQ resources is orthogonal to the question of
> > whether you should use pnp_register_driver() or acpi_walk_namespace().
> When we detect the IPMI system interface by loading PNP device driver,
> the advantage is that it can re-use the parse mechanism of
> IO/memory/interrupt. Right?
> In fact we will have to evaluate the following ACPI object:
> 	>_IFT, _GPE, _SRV
> 
> If there exists the _GPE object, it is unnecessary to parse the resource
> related with the interrupt.
> 
> At the same time as I mentioned in the previous email, sometimes we will
> get the two different IO address definitions after evaluating the _CRS
> object. Which should be selected?
> If there exist both IO and memory address definition in _CRS object,
> which should be selected?

You have to decide which address to use whether you learn the addresses
by using acpi_walk_resources() or by looking through the resources
decoded by PNPACPI.  Using acpi_walk_resources() doesn't make that
choice any easier.

> > PNPACPI parses the IPMI device resources for every ACPI device,
> > including the IPMI device, before we even know whether there will be
> > a PNP driver for the device.  It's much easier to look at the PNP
> > resources and figure out which to use than it is to use
> > acpi_walk_resources() manually.
> > 
> > The main point is that ipmi_si_intf.c is a device driver, and it should
> > use the normal driver registration mechanisms.  I think it would be
> > simplest and clearest to make a few PNP enhancements so it could use
> > pnp_register_driver(), but even using acpi_bus_register_driver() would
> > be fine.  Using acpi_walk_namespace() to do everything by hand is just
> > completely wrong.
> The main purpose is to detect the IPMI system interface defined in ACPI
> table.  If the device can be detected correctly, IMO it will be OK.

It is important to detect the device.  It is also important to have a
mechanism to prevent two drivers from thinking they own the same device.

> Why do think that it is wrong to use the acpi_walk_namespace to parse
> the resource?

You're using acpi_walk_namespace() to locate the device, not to parse
the resources.  You use acpi_walk_resources() to parse the resources.

The fact that your patch uses acpi_walk_namespace() to find the
device means that ipmi_si_intf.c can be talking to a device, but the
rest of the system doesn't know ipmi_si_intf.c "owns" it.  So another
driver B could come along and correctly use acpi_bus_register_driver()
with the IPMI IDs.  The Linux ACPI core knows nothing about the fact
that ipmi_si_intf.c thinks it "owns" the IPMI device, so it will call
the driver B "add" method.  Now we have two drivers that both think
they own the device.  This leads to chaos.

Bjorn


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On Wed, 2009-10-28 at 13:11 +0800, Bjorn Helgaas wrote:
> On Wed, 2009-10-28 at 10:50 +0800, ykzhao wrote:
> > On Tue, 2009-10-27 at 23:38 +0800, Bjorn Helgaas wrote:
> > > On Monday 26 October 2009 07:02:55 pm ykzhao wrote:
> > > > In fact you mention two issues about the two patches:
> > > >    1: Load a PNP driver for it to register the IPMI system interface.
> > > > This is about the first patch.
> > > >    2. coding style( for example: comments, the definition about some
> > > > variables).
> > > > 
> > > > For the first issue: Before I start the first patch, I consider using
> > > > the PNP device driver. But I find that it is so complex because of the
> > > > following two points:
> > > >     1. One is that we can't register the IPMI system interface if the
> > > > boot option of "pnpacpi=off" is added. This will also depend on the PNP
> > > > module.
> > > 
> > > This is not a problem.  It is perfectly acceptable for the IPMI driver
> > > to depend on PNP and PNPACPI in order to claim an ACPI device.  If the
> > > users boots with "pnpacpi=off", we just won't find an IPMI device.
> > > That is the way it works for TPM devices and serial devices described
> > > by ACPI, and IPMI should work the same way.
> > Yes. Several methods can be used to detect the IPMI system interface.
> > In such case it still can be detected by using other method when the
> > ACPI detection mechanism is disabled. But the acpi detection mechanism
> > will depend on the ACPI and PNP subsystem if we detect the IMPI system
> > interface defined in ACPI table by using PNP device driver. 
> > 
> > At the same time there exist two ACPI detection mechanisms. One is
> > defined in SPMI table. The other is defined in ACPI table. We expect
> > that the two ACPI detection mechanisms depend on the same judgement
> > condition. 
> > So I prefer to detect the IPMI system interface when ACPI enabled
> > regardless of the boot option of "pnpacpi=off".
> 
> The IPMI driver is not special.  It should behave like all other
> drivers.  There is no reason it should handle the "pnpacpi=off" case
> differently than other drivers.
> 
> But if you change this to use acpi_bus_register_driver(), there will be
> no PNP dependency, "pnpacpi=off" will have no effect either way, and
> I'll be happy.  I don't think it's the cleanest solution, but it at
> least gives us a chance to properly bind the driver to the device.
This patch set includes two parts. One is to detect the IPMI system
interface defined in ACPI table and register it. The other is to allow
the ACPI AML code to communicate with the IPMI system interface. 

As an device driver is already bound to the device in the second patch,
it is impossible that we load another device driver for the same IPMI
device.
> > > >     2. The second is that there exist so many cases about the IPMI
> > > > IO/memory resource definition. Maybe there exist both IO/memory resource
> > > > definition for one IPMI device. In such case we can't know which should
> > > > be selected. At the same time we have similar issues about the interrupt
> > > > type. So I decide to parse the IO/memory/interrupt resource
> > > > independently.
> > > 
> > > This doesn't make any sense.  The fact that an IPMI device might have
> > > a variety of IO/memory/IRQ resources is orthogonal to the question of
> > > whether you should use pnp_register_driver() or acpi_walk_namespace().
> > When we detect the IPMI system interface by loading PNP device driver,
> > the advantage is that it can re-use the parse mechanism of
> > IO/memory/interrupt. Right?
> > In fact we will have to evaluate the following ACPI object:
> > 	>_IFT, _GPE, _SRV
> > 
> > If there exists the _GPE object, it is unnecessary to parse the resource
> > related with the interrupt.
> > 
> > At the same time as I mentioned in the previous email, sometimes we will
> > get the two different IO address definitions after evaluating the _CRS
> > object. Which should be selected?
> > If there exist both IO and memory address definition in _CRS object,
> > which should be selected?
> 
> You have to decide which address to use whether you learn the addresses
> by using acpi_walk_resources() or by looking through the resources
> decoded by PNPACPI.  Using acpi_walk_resources() doesn't make that
> choice any easier.
> 
> > > PNPACPI parses the IPMI device resources for every ACPI device,
> > > including the IPMI device, before we even know whether there will be
> > > a PNP driver for the device.  It's much easier to look at the PNP
> > > resources and figure out which to use than it is to use
> > > acpi_walk_resources() manually.
> > > 
> > > The main point is that ipmi_si_intf.c is a device driver, and it should
> > > use the normal driver registration mechanisms.  I think it would be
> > > simplest and clearest to make a few PNP enhancements so it could use
> > > pnp_register_driver(), but even using acpi_bus_register_driver() would
> > > be fine.  Using acpi_walk_namespace() to do everything by hand is just
> > > completely wrong.
> > The main purpose is to detect the IPMI system interface defined in ACPI
> > table.  If the device can be detected correctly, IMO it will be OK.
> 
> It is important to detect the device.  It is also important to have a
> mechanism to prevent two drivers from thinking they own the same device.
> 
> > Why do think that it is wrong to use the acpi_walk_namespace to parse
> > the resource?
> 
> You're using acpi_walk_namespace() to locate the device, not to parse
> the resources.  You use acpi_walk_resources() to parse the resources.
Is it wrong to use acpi_walk_namespace to locate the device?
Why we can't use the acpi_walk_resources directly to parse the
corresponding resource? 
> The fact that your patch uses acpi_walk_namespace() to find the
> device means that ipmi_si_intf.c can be talking to a device, but the
> rest of the system doesn't know ipmi_si_intf.c "owns" it.  So another
> driver B could come along and correctly use acpi_bus_register_driver()
> with the IPMI IDs.  The Linux ACPI core knows nothing about the fact
> that ipmi_si_intf.c thinks it "owns" the IPMI device, so it will call
> the driver B "add" method.  Now we have two drivers that both think
> they own the device.  This leads to chaos.
Why is it necessary that the reset of the system doesn't know
ipmi_si_intf.c "owns" the IPMI system interface?
In fact the main purpose of ipmi_si_intf.c is to detect the available
IPMI system interface on a system. And then this interface can be used
by system management software.


> Bjorn
> 
> 

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On Wed, 2009-10-28 at 17:51 +0800, ykzhao wrote:
> On Wed, 2009-10-28 at 13:11 +0800, Bjorn Helgaas wrote:
> > On Wed, 2009-10-28 at 10:50 +0800, ykzhao wrote:
> > > On Tue, 2009-10-27 at 23:38 +0800, Bjorn Helgaas wrote:
> > > > On Monday 26 October 2009 07:02:55 pm ykzhao wrote:
> > > > > In fact you mention two issues about the two patches:
> > > > >    1: Load a PNP driver for it to register the IPMI system interface.
> > > > > This is about the first patch.
> > > > >    2. coding style( for example: comments, the definition about some
> > > > > variables).
> > > > > 
> > > > > For the first issue: Before I start the first patch, I consider using
> > > > > the PNP device driver. But I find that it is so complex because of the
> > > > > following two points:
> > > > >     1. One is that we can't register the IPMI system interface if the
> > > > > boot option of "pnpacpi=off" is added. This will also depend on the PNP
> > > > > module.
> > > > 
> > > > This is not a problem.  It is perfectly acceptable for the IPMI driver
> > > > to depend on PNP and PNPACPI in order to claim an ACPI device.  If the
> > > > users boots with "pnpacpi=off", we just won't find an IPMI device.
> > > > That is the way it works for TPM devices and serial devices described
> > > > by ACPI, and IPMI should work the same way.
> > > Yes. Several methods can be used to detect the IPMI system interface.
> > > In such case it still can be detected by using other method when the
> > > ACPI detection mechanism is disabled. But the acpi detection mechanism
> > > will depend on the ACPI and PNP subsystem if we detect the IMPI system
> > > interface defined in ACPI table by using PNP device driver. 
> > > 
> > > At the same time there exist two ACPI detection mechanisms. One is
> > > defined in SPMI table. The other is defined in ACPI table. We expect
> > > that the two ACPI detection mechanisms depend on the same judgement
> > > condition. 
> > > So I prefer to detect the IPMI system interface when ACPI enabled
> > > regardless of the boot option of "pnpacpi=off".
> > 
> > The IPMI driver is not special.  It should behave like all other
> > drivers.  There is no reason it should handle the "pnpacpi=off" case
> > differently than other drivers.
> > 
> > But if you change this to use acpi_bus_register_driver(), there will be
> > no PNP dependency, "pnpacpi=off" will have no effect either way, and
> > I'll be happy.  I don't think it's the cleanest solution, but it at
> > least gives us a chance to properly bind the driver to the device.
> This patch set includes two parts. One is to detect the IPMI system
> interface defined in ACPI table and register it. The other is to allow
> the ACPI AML code to communicate with the IPMI system interface. 
> 
> As an device driver is already bound to the device in the second patch,
> it is impossible that we load another device driver for the same IPMI
> device.

I know.  That's why in my original responses a month ago, I suggested
that you integrate these two parts.  From the Linux point of view, one
piece of hardware gets one driver.  If you need two parts internally,
that's an implementation concern of the driver.  From the point of view
of the Linux/ACPI and PNP code, there must be a single driver.

> > > > >     2. The second is that there exist so many cases about the IPMI
> > > > > IO/memory resource definition. Maybe there exist both IO/memory resource
> > > > > definition for one IPMI device. In such case we can't know which should
> > > > > be selected. At the same time we have similar issues about the interrupt
> > > > > type. So I decide to parse the IO/memory/interrupt resource
> > > > > independently.
> > > > 
> > > > This doesn't make any sense.  The fact that an IPMI device might have
> > > > a variety of IO/memory/IRQ resources is orthogonal to the question of
> > > > whether you should use pnp_register_driver() or acpi_walk_namespace().
> > > When we detect the IPMI system interface by loading PNP device driver,
> > > the advantage is that it can re-use the parse mechanism of
> > > IO/memory/interrupt. Right?
> > > In fact we will have to evaluate the following ACPI object:
> > > 	>_IFT, _GPE, _SRV
> > > 
> > > If there exists the _GPE object, it is unnecessary to parse the resource
> > > related with the interrupt.
> > > 
> > > At the same time as I mentioned in the previous email, sometimes we will
> > > get the two different IO address definitions after evaluating the _CRS
> > > object. Which should be selected?
> > > If there exist both IO and memory address definition in _CRS object,
> > > which should be selected?
> > 
> > You have to decide which address to use whether you learn the addresses
> > by using acpi_walk_resources() or by looking through the resources
> > decoded by PNPACPI.  Using acpi_walk_resources() doesn't make that
> > choice any easier.
> > 
> > > > PNPACPI parses the IPMI device resources for every ACPI device,
> > > > including the IPMI device, before we even know whether there will be
> > > > a PNP driver for the device.  It's much easier to look at the PNP
> > > > resources and figure out which to use than it is to use
> > > > acpi_walk_resources() manually.
> > > > 
> > > > The main point is that ipmi_si_intf.c is a device driver, and it should
> > > > use the normal driver registration mechanisms.  I think it would be
> > > > simplest and clearest to make a few PNP enhancements so it could use
> > > > pnp_register_driver(), but even using acpi_bus_register_driver() would
> > > > be fine.  Using acpi_walk_namespace() to do everything by hand is just
> > > > completely wrong.
> > > The main purpose is to detect the IPMI system interface defined in ACPI
> > > table.  If the device can be detected correctly, IMO it will be OK.
> > 
> > It is important to detect the device.  It is also important to have a
> > mechanism to prevent two drivers from thinking they own the same device.
> > 
> > > Why do think that it is wrong to use the acpi_walk_namespace to parse
> > > the resource?
> > 
> > You're using acpi_walk_namespace() to locate the device, not to parse
> > the resources.  You use acpi_walk_resources() to parse the resources.
> Is it wrong to use acpi_walk_namespace to locate the device?

Yes, for the reason I explained below.  To repeat myself, you must use
acpi_bus_register_driver() (or pnp_register_driver()) so we can prevent
multiple drivers from claiming the same piece of hardware.

[There is an existing PNPACPI problem in that I think we currently allow
a driver using acpi_bus_register_driver() and a driver using
pnp_register_driver() to both claim the same device.  But this is an
existing issue with the Linux/ACPI and PNPACPI core, not with the
drivers themselves.]

> Why we can't use the acpi_walk_resources directly to parse the
> corresponding resource?

You can.  I think it would be easier in the long run to rely on the
resource parsing done by PNPACPI, but you can use acpi_walk_resources()
if you want to.

> > The fact that your patch uses acpi_walk_namespace() to find the
> > device means that ipmi_si_intf.c can be talking to a device, but the
> > rest of the system doesn't know ipmi_si_intf.c "owns" it.  So another
> > driver B could come along and correctly use acpi_bus_register_driver()
> > with the IPMI IDs.  The Linux ACPI core knows nothing about the fact
> > that ipmi_si_intf.c thinks it "owns" the IPMI device, so it will call
> > the driver B "add" method.  Now we have two drivers that both think
> > they own the device.  This leads to chaos.
> Why is it necessary that the reset of the system doesn't know
> ipmi_si_intf.c "owns" the IPMI system interface?

Using acpi_bus_register_driver() lets the Linux/ACPI core make sure that
only a single driver is bound to the device.  If two drivers bind to it,
they will interfere with each other.

Bjorn


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On Thu, 2009-10-29 at 00:49 +0800, Bjorn Helgaas wrote:
> On Wed, 2009-10-28 at 17:51 +0800, ykzhao wrote:
> > On Wed, 2009-10-28 at 13:11 +0800, Bjorn Helgaas wrote:
> > > On Wed, 2009-10-28 at 10:50 +0800, ykzhao wrote:
> > > > On Tue, 2009-10-27 at 23:38 +0800, Bjorn Helgaas wrote:
> > > > > On Monday 26 October 2009 07:02:55 pm ykzhao wrote:
> > > > > > In fact you mention two issues about the two patches:
> > > > > >    1: Load a PNP driver for it to register the IPMI system interface.
> > > > > > This is about the first patch.
> > > > > >    2. coding style( for example: comments, the definition about some
> > > > > > variables).
> > > > > > 
> > > > > > For the first issue: Before I start the first patch, I consider using
> > > > > > the PNP device driver. But I find that it is so complex because of the
> > > > > > following two points:
> > > > > >     1. One is that we can't register the IPMI system interface if the
> > > > > > boot option of "pnpacpi=off" is added. This will also depend on the PNP
> > > > > > module.
> > > > > 
> > > > > This is not a problem.  It is perfectly acceptable for the IPMI driver
> > > > > to depend on PNP and PNPACPI in order to claim an ACPI device.  If the
> > > > > users boots with "pnpacpi=off", we just won't find an IPMI device.
> > > > > That is the way it works for TPM devices and serial devices described
> > > > > by ACPI, and IPMI should work the same way.
> > > > Yes. Several methods can be used to detect the IPMI system interface.
> > > > In such case it still can be detected by using other method when the
> > > > ACPI detection mechanism is disabled. But the acpi detection mechanism
> > > > will depend on the ACPI and PNP subsystem if we detect the IMPI system
> > > > interface defined in ACPI table by using PNP device driver. 
> > > > 
> > > > At the same time there exist two ACPI detection mechanisms. One is
> > > > defined in SPMI table. The other is defined in ACPI table. We expect
> > > > that the two ACPI detection mechanisms depend on the same judgement
> > > > condition. 
> > > > So I prefer to detect the IPMI system interface when ACPI enabled
> > > > regardless of the boot option of "pnpacpi=off".
> > > 
> > > The IPMI driver is not special.  It should behave like all other
> > > drivers.  There is no reason it should handle the "pnpacpi=off" case
> > > differently than other drivers.
> > > 
> > > But if you change this to use acpi_bus_register_driver(), there will be
> > > no PNP dependency, "pnpacpi=off" will have no effect either way, and
> > > I'll be happy.  I don't think it's the cleanest solution, but it at
> > > least gives us a chance to properly bind the driver to the device.
> > This patch set includes two parts. One is to detect the IPMI system
> > interface defined in ACPI table and register it. The other is to allow
> > the ACPI AML code to communicate with the IPMI system interface. 
> > 
> > As an device driver is already bound to the device in the second patch,
> > it is impossible that we load another device driver for the same IPMI
> > device.
> 
> I know.  That's why in my original responses a month ago, I suggested
> that you integrate these two parts.  From the Linux point of view, one
> piece of hardware gets one driver.  If you need two parts internally,
> that's an implementation concern of the driver.  From the point of view
> of the Linux/ACPI and PNP code, there must be a single driver.
Two patches can work independently. One it to detect and register the
IPMI system interface. Then the interface can be used by system
management software. Of course the ACPI AML code can create a channel to
communicate with the system interface.
The second is to create the relationship between ACPI AML code and IPMI
system interface(BMC). If the same IPMI system interface can be
registered by several methods(DMI, hardcode, default . etc). This patch
can work even without the first patch.

At the same time we will have to consider another issue. As we know, the
IPMI system interface is registered by using the function of
try_smi_init. But this function is defined as static function and we
can't call it out of ipmi_si_intf.c.
If we add the corresponding ACPI driver in the file of ipmi_si_intf.c,
it will be OK to merge them into one part. But this is a bad idea. The
acpi driver is located in the IPMI subsystem. Confusing?
> 
> > > > > >     2. The second is that there exist so many cases about the IPMI
> > > > > > IO/memory resource definition. Maybe there exist both IO/memory resource
> > > > > > definition for one IPMI device. In such case we can't know which should
> > > > > > be selected. At the same time we have similar issues about the interrupt
> > > > > > type. So I decide to parse the IO/memory/interrupt resource
> > > > > > independently.
> > > > > 
> > > > > This doesn't make any sense.  The fact that an IPMI device might have
> > > > > a variety of IO/memory/IRQ resources is orthogonal to the question of
> > > > > whether you should use pnp_register_driver() or acpi_walk_namespace().
> > > > When we detect the IPMI system interface by loading PNP device driver,
> > > > the advantage is that it can re-use the parse mechanism of
> > > > IO/memory/interrupt. Right?
> > > > In fact we will have to evaluate the following ACPI object:
> > > > 	>_IFT, _GPE, _SRV
> > > > 
> > > > If there exists the _GPE object, it is unnecessary to parse the resource
> > > > related with the interrupt.
> > > > 
> > > > At the same time as I mentioned in the previous email, sometimes we will
> > > > get the two different IO address definitions after evaluating the _CRS
> > > > object. Which should be selected?
> > > > If there exist both IO and memory address definition in _CRS object,
> > > > which should be selected?
> > > 
> > > You have to decide which address to use whether you learn the addresses
> > > by using acpi_walk_resources() or by looking through the resources
> > > decoded by PNPACPI.  Using acpi_walk_resources() doesn't make that
> > > choice any easier.
> > > 
> > > > > PNPACPI parses the IPMI device resources for every ACPI device,
> > > > > including the IPMI device, before we even know whether there will be
> > > > > a PNP driver for the device.  It's much easier to look at the PNP
> > > > > resources and figure out which to use than it is to use
> > > > > acpi_walk_resources() manually.
> > > > > 
> > > > > The main point is that ipmi_si_intf.c is a device driver, and it should
> > > > > use the normal driver registration mechanisms.  I think it would be
> > > > > simplest and clearest to make a few PNP enhancements so it could use
> > > > > pnp_register_driver(), but even using acpi_bus_register_driver() would
> > > > > be fine.  Using acpi_walk_namespace() to do everything by hand is just
> > > > > completely wrong.
> > > > The main purpose is to detect the IPMI system interface defined in ACPI
> > > > table.  If the device can be detected correctly, IMO it will be OK.
> > > 
> > > It is important to detect the device.  It is also important to have a
> > > mechanism to prevent two drivers from thinking they own the same device.
> > > 
> > > > Why do think that it is wrong to use the acpi_walk_namespace to parse
> > > > the resource?
> > > 
> > > You're using acpi_walk_namespace() to locate the device, not to parse
> > > the resources.  You use acpi_walk_resources() to parse the resources.
> > Is it wrong to use acpi_walk_namespace to locate the device?
> 
> Yes, for the reason I explained below.  To repeat myself, you must use
> acpi_bus_register_driver() (or pnp_register_driver()) so we can prevent
> multiple drivers from claiming the same piece of hardware.
> 
> [There is an existing PNPACPI problem in that I think we currently allow
> a driver using acpi_bus_register_driver() and a driver using
> pnp_register_driver() to both claim the same device.  But this is an
> existing issue with the Linux/ACPI and PNPACPI core, not with the
> drivers themselves.]
> 
> > Why we can't use the acpi_walk_resources directly to parse the
> > corresponding resource?
> 
> You can.  I think it would be easier in the long run to rely on the
> resource parsing done by PNPACPI, but you can use acpi_walk_resources()
> if you want to.
> 
> > > The fact that your patch uses acpi_walk_namespace() to find the
> > > device means that ipmi_si_intf.c can be talking to a device, but the
> > > rest of the system doesn't know ipmi_si_intf.c "owns" it.  So another
> > > driver B could come along and correctly use acpi_bus_register_driver()
> > > with the IPMI IDs.  The Linux ACPI core knows nothing about the fact
> > > that ipmi_si_intf.c thinks it "owns" the IPMI device, so it will call
> > > the driver B "add" method.  Now we have two drivers that both think
> > > they own the device.  This leads to chaos.
> > Why is it necessary that the reset of the system doesn't know
> > ipmi_si_intf.c "owns" the IPMI system interface?
> 
> Using acpi_bus_register_driver() lets the Linux/ACPI core make sure that
> only a single driver is bound to the device.  If two drivers bind to it,
> they will interfere with each other.
> 
> Bjorn
> 
> 

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