[v3,05/40] misc/mei/hdcp: Notifier chain for mei cldev state change

Commit Message

Ramalingam C April 3, 2018, 1:57 p.m. UTC

Notifier Chain is defined to inform all its clients about the mei
client device state change. Routine is defined for the clients to
register and unregister for the notification on state change.

v2:
  Rebased.
v3:
  Notifier chain is adopted for cldev state update [Tomas]

Signed-off-by: Ramalingam C <[e-mail]>
---
 drivers/misc/mei/hdcp/mei_hdcp.c | 36 +++++++++++++++++++++++++++---
 include/linux/mei_hdcp.h         | 48 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 81 insertions(+), 3 deletions(-)
 create mode 100644 include/linux/mei_hdcp.h

Comments

Daniel Vetter April 3, 2018, 3:30 p.m. UTC | #1

On Tue, Apr 03, 2018 at 07:27:18PM +0530, Ramalingam C wrote:
> Notifier Chain is defined to inform all its clients about the mei
> client device state change. Routine is defined for the clients to
> register and unregister for the notification on state change.
> 
> v2:
>   Rebased.
> v3:
>   Notifier chain is adopted for cldev state update [Tomas]
> 
> Signed-off-by: Ramalingam C <[e-mail]>

For managing interactions between multiple drivers notifier chains are
fairly problematic. The main reason is the locking embedded in the
notifier chain. To make things safe, that lock must be held everytime we
add/remove any part of the link, and when calling any callback. Usually
that means you get a neat deadlock sooner or later, because the
load/unload code has inverse paths compared to normal operation.

Notifiers also not not provide a clean way to handle suspend/resume
ordering.

There's two parts to do this properly.

1. Finding the other driver. Multi-part drivers are assembled nowadays
using the component framework. We're using that already to manage the
interaction between drm/i915 and snd-hda. If not all components are ready
yet, then the driver load sequence must be aborted by returning
-EPROBE_DEFER. That's going to be lots of fun, since for the mei/i915
interaction it's probably going to be i915 that needs to abort and retry
the driver load. But we do CI test all the abort points in our driver
load, so should work well.

2. Handling the ordering restrictions for suspend/resume. For i915/snd-hda
we used a early_resume/late_suspend callback trickery, but that doesn't
really scale to multiple levels. Since we've done that device_link has
been added. As a bonus device_link can also ensure that not only
suspend/resume (including runtime suspend/resume) is ordered correctly,
but also that driver bind/unbind works correctly. Still needs the
component stuff and initial -EPROBE_DEFER, but will all least make sure
we' only reprobe once more. See device_link_add + docs in device_link.rst.

One thing I didn't check is whether we want the device linke to also
manage runtime pm for us. It would mean that we keep the ME awake as long
as anything is using the gpu (any display on or any rendering happening).
That might be too much, but could also be that it won't matter (and then
using DL_FLAG_PM_RUNTIME would simply our code).

We might also need to convert the i915/snd-hda interactions to device_link
first, since the early/late_resume/suspend hack probably doesn't interact
too well with proper device_links.

Cheers, Daniel

> ---
>  drivers/misc/mei/hdcp/mei_hdcp.c | 36 +++++++++++++++++++++++++++---
>  include/linux/mei_hdcp.h         | 48 ++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 81 insertions(+), 3 deletions(-)
>  create mode 100644 include/linux/mei_hdcp.h
> 
> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c b/drivers/misc/mei/hdcp/mei_hdcp.c
> index b334615728a7..2811a25f8c57 100644
> --- a/drivers/misc/mei/hdcp/mei_hdcp.c
> +++ b/drivers/misc/mei/hdcp/mei_hdcp.c
> @@ -31,6 +31,32 @@
>  #include <linux/slab.h>
>  #include <linux/uuid.h>
>  #include <linux/mei_cl_bus.h>
> +#include <linux/notifier.h>
> +#include <linux/mei_hdcp.h>
> +
> +static BLOCKING_NOTIFIER_HEAD(mei_cldev_notifier_list);
> +
> +void mei_cldev_state_notify_clients(struct mei_cl_device *cldev, bool enabled)
> +{
> +	if (enabled)
> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,
> +					     MEI_CLDEV_ENABLED, cldev);
> +	else
> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,
> +					     MEI_CLDEV_DISABLED, NULL);
> +}
> +
> +int mei_cldev_register_notify(struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_register(&mei_cldev_notifier_list, nb);
> +}
> +EXPORT_SYMBOL_GPL(mei_cldev_register_notify);
> +
> +int mei_cldev_unregister_notify(struct notifier_block *nb)
> +{
> +	return blocking_notifier_chain_unregister(&mei_cldev_notifier_list, nb);
> +}
> +EXPORT_SYMBOL_GPL(mei_cldev_unregister_notify);
>  
>  static int mei_hdcp_probe(struct mei_cl_device *cldev,
>  			  const struct mei_cl_device_id *id)
> @@ -38,14 +64,18 @@ static int mei_hdcp_probe(struct mei_cl_device *cldev,
>  	int ret;
>  
>  	ret = mei_cldev_enable(cldev);
> -	if (ret < 0)
> +	if (ret < 0) {
>  		dev_err(&cldev->dev, "mei_cldev_enable Failed. %d\n", ret);
> +		return ret;
> +	}
>  
> -	return ret;
> +	mei_cldev_state_notify_clients(cldev, true);
> +	return 0;
>  }
>  
>  static int mei_hdcp_remove(struct mei_cl_device *cldev)
>  {
> +	mei_cldev_state_notify_clients(cldev, false);
>  	mei_cldev_set_drvdata(cldev, NULL);
>  	return mei_cldev_disable(cldev);
>  }
> @@ -71,4 +101,4 @@ module_mei_cl_driver(mei_hdcp_driver);
>  
>  MODULE_AUTHOR("Intel Corporation");
>  MODULE_LICENSE("Dual BSD/GPL");
> -MODULE_DESCRIPTION("HDCP");
> +MODULE_DESCRIPTION("MEI HDCP");
> diff --git a/include/linux/mei_hdcp.h b/include/linux/mei_hdcp.h
> new file mode 100644
> index 000000000000..3b46bebde718
> --- /dev/null
> +++ b/include/linux/mei_hdcp.h
> @@ -0,0 +1,48 @@
> +/* SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause) */
> +/*
> + * Copyright © 2017-2018 Intel Corporation
> + *
> + * Permission to use, copy, modify, distribute, and sell this software and its
> + * documentation for any purpose is hereby granted without fee, provided that
> + * the above copyright notice appear in all copies and that both that copyright
> + * notice and this permission notice appear in supporting documentation, and
> + * that the name of the copyright holders not be used in advertising or
> + * publicity pertaining to distribution of the software without specific,
> + * written prior permission.  The copyright holders make no representations
> + * about the suitability of this software for any purpose.  It is provided "as
> + * is" without express or implied warranty.
> + *
> + * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
> + * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
> + * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
> + * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
> + * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
> + * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
> + * OF THIS SOFTWARE.
> + *
> + * Authors:
> + *	Ramalingam C <[e-mail]>
> + */
> +
> +#ifndef _LINUX_MEI_HDCP_H
> +#define _LINUX_MEI_HDCP_H
> +
> +enum mei_cldev_state {
> +	MEI_CLDEV_DISABLED,
> +	MEI_CLDEV_ENABLED
> +};
> +
> +#ifdef CONFIG_INTEL_MEI_HDCP
> +int mei_cldev_register_notify(struct notifier_block *nb);
> +int mei_cldev_unregister_notify(struct notifier_block *nb);
> +#else
> +static int mei_cldev_register_notify(struct notifier_block *nb)
> +{
> +	return -ENODEV;
> +}
> +static int mei_cldev_unregister_notify(struct notifier_block *nb)
> +{
> +	return -ENODEV;
> +}
> +#endif /* defined (CONFIG_INTEL_MEI_HDCP) */
> +#endif /* defined (_LINUX_MEI_HDCP_H) */
> -- 
> 2.7.4
>

kernel test robot April 3, 2018, 8:53 p.m. UTC | #2

Hi Ramalingam,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on drm-intel/for-linux-next]
[also build test ERROR on next-20180403]
[cannot apply to v4.16]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Ramalingam-C/drm-i915-Implement-HDCP2-2/20180404-031743
base:   git://anongit.freedesktop.org/drm-intel for-linux-next
config: i386-allmodconfig (attached as .config)
compiler: gcc-7 (Debian 7.3.0-1) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

>> drivers/misc/mei/hdcp/mei_hdcp.c:49:5: error: redefinition of 'mei_cldev_register_notify'
    int mei_cldev_register_notify(struct notifier_block *nb)
        ^~~~~~~~~~~~~~~~~~~~~~~~~
   In file included from drivers/misc/mei/hdcp/mei_hdcp.c:35:0:
   include/linux/mei_hdcp.h:39:12: note: previous definition of 'mei_cldev_register_notify' was here
    static int mei_cldev_register_notify(struct notifier_block *nb)
               ^~~~~~~~~~~~~~~~~~~~~~~~~
>> drivers/misc/mei/hdcp/mei_hdcp.c:55:5: error: redefinition of 'mei_cldev_unregister_notify'
    int mei_cldev_unregister_notify(struct notifier_block *nb)
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   In file included from drivers/misc/mei/hdcp/mei_hdcp.c:35:0:
   include/linux/mei_hdcp.h:43:12: note: previous definition of 'mei_cldev_unregister_notify' was here
    static int mei_cldev_unregister_notify(struct notifier_block *nb)
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~
   include/linux/mei_hdcp.h:43:12: warning: 'mei_cldev_unregister_notify' defined but not used [-Wunused-function]
   include/linux/mei_hdcp.h:39:12: warning: 'mei_cldev_register_notify' defined but not used [-Wunused-function]
    static int mei_cldev_register_notify(struct notifier_block *nb)
               ^~~~~~~~~~~~~~~~~~~~~~~~~

vim +/mei_cldev_register_notify +49 drivers/misc/mei/hdcp/mei_hdcp.c

    48	
  > 49	int mei_cldev_register_notify(struct notifier_block *nb)
    50	{
    51		return blocking_notifier_chain_register(&mei_cldev_notifier_list, nb);
    52	}
    53	EXPORT_SYMBOL_GPL(mei_cldev_register_notify);
    54	
  > 55	int mei_cldev_unregister_notify(struct notifier_block *nb)
    56	{
    57		return blocking_notifier_chain_unregister(&mei_cldev_notifier_list, nb);
    58	}
    59	EXPORT_SYMBOL_GPL(mei_cldev_unregister_notify);
    60	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

Alexander Usyskin April 4, 2018, 6:12 a.m. UTC | #3

> -----Original Message-----

> From: C, Ramalingam

> Sent: Tuesday, April 03, 2018 16:57

> To: [e-mail]; [e-mail];

> [e-mail]; [e-mail]; [e-mail];

> [e-mail]; Winkler, Tomas <[e-mail]>;

> Usyskin, Alexander <[e-mail]>

> Cc: Vivi, Rodrigo <[e-mail]>; C, Ramalingam

> <[e-mail]>

> Subject: [PATCH v3 05/40] misc/mei/hdcp: Notifier chain for mei cldev state

> change

> 

> Notifier Chain is defined to inform all its clients about the mei

> client device state change. Routine is defined for the clients to

> register and unregister for the notification on state change.

> 

> v2:

>   Rebased.

> v3:

>   Notifier chain is adopted for cldev state update [Tomas]

> 

> Signed-off-by: Ramalingam C <[e-mail]>

> ---


May be I miss something, but bus subsystem already has notifier chain. (BUS_NOTIFY_ADD_DEVICE etc.)
We only ought to make mei_cl_bus_type available in header.

>  drivers/misc/mei/hdcp/mei_hdcp.c | 36 +++++++++++++++++++++++++++---

>  include/linux/mei_hdcp.h         | 48

> ++++++++++++++++++++++++++++++++++++++++

>  2 files changed, 81 insertions(+), 3 deletions(-)

>  create mode 100644 include/linux/mei_hdcp.h

> 

> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c

> b/drivers/misc/mei/hdcp/mei_hdcp.c

> index b334615728a7..2811a25f8c57 100644

> --- a/drivers/misc/mei/hdcp/mei_hdcp.c

> +++ b/drivers/misc/mei/hdcp/mei_hdcp.c

> @@ -31,6 +31,32 @@

>  #include <linux/slab.h>

>  #include <linux/uuid.h>

>  #include <linux/mei_cl_bus.h>

> +#include <linux/notifier.h>

> +#include <linux/mei_hdcp.h>

> +

> +static BLOCKING_NOTIFIER_HEAD(mei_cldev_notifier_list);

> +

> +void mei_cldev_state_notify_clients(struct mei_cl_device *cldev, bool

> enabled)

> +{

> +	if (enabled)

> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,

> +					     MEI_CLDEV_ENABLED, cldev);

> +	else

> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,

> +					     MEI_CLDEV_DISABLED, NULL);

> +}

> +

> +int mei_cldev_register_notify(struct notifier_block *nb)

> +{

> +	return blocking_notifier_chain_register(&mei_cldev_notifier_list,

> nb);

> +}

> +EXPORT_SYMBOL_GPL(mei_cldev_register_notify);

> +

> +int mei_cldev_unregister_notify(struct notifier_block *nb)

> +{

> +	return blocking_notifier_chain_unregister(&mei_cldev_notifier_list,

> nb);

> +}

> +EXPORT_SYMBOL_GPL(mei_cldev_unregister_notify);

> 

>  static int mei_hdcp_probe(struct mei_cl_device *cldev,

>  			  const struct mei_cl_device_id *id)

> @@ -38,14 +64,18 @@ static int mei_hdcp_probe(struct mei_cl_device

> *cldev,

>  	int ret;

> 

>  	ret = mei_cldev_enable(cldev);

> -	if (ret < 0)

> +	if (ret < 0) {

>  		dev_err(&cldev->dev, "mei_cldev_enable Failed. %d\n", ret);

> +		return ret;

> +	}

> 

> -	return ret;

> +	mei_cldev_state_notify_clients(cldev, true);

> +	return 0;

>  }

> 

>  static int mei_hdcp_remove(struct mei_cl_device *cldev)

>  {

> +	mei_cldev_state_notify_clients(cldev, false);

>  	mei_cldev_set_drvdata(cldev, NULL);

>  	return mei_cldev_disable(cldev);

>  }

> @@ -71,4 +101,4 @@ module_mei_cl_driver(mei_hdcp_driver);

> 

>  MODULE_AUTHOR("Intel Corporation");

>  MODULE_LICENSE("Dual BSD/GPL");

> -MODULE_DESCRIPTION("HDCP");

> +MODULE_DESCRIPTION("MEI HDCP");

> diff --git a/include/linux/mei_hdcp.h b/include/linux/mei_hdcp.h

> new file mode 100644

> index 000000000000..3b46bebde718

> --- /dev/null

> +++ b/include/linux/mei_hdcp.h

> @@ -0,0 +1,48 @@

> +/* SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause) */

> +/*

> + * Copyright © 2017-2018 Intel Corporation

> + *

> + * Permission to use, copy, modify, distribute, and sell this software and its

> + * documentation for any purpose is hereby granted without fee, provided

> that

> + * the above copyright notice appear in all copies and that both that

> copyright

> + * notice and this permission notice appear in supporting documentation,

> and

> + * that the name of the copyright holders not be used in advertising or

> + * publicity pertaining to distribution of the software without specific,

> + * written prior permission.  The copyright holders make no representations

> + * about the suitability of this software for any purpose.  It is provided "as

> + * is" without express or implied warranty.

> + *

> + * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO

> THIS SOFTWARE,

> + * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND

> FITNESS, IN NO

> + * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL,

> INDIRECT OR

> + * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING

> FROM LOSS OF USE,

> + * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE

> OR OTHER

> + * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE

> OR PERFORMANCE

> + * OF THIS SOFTWARE.

> + *

> + * Authors:

> + *	Ramalingam C <[e-mail]>

> + */

> +

> +#ifndef _LINUX_MEI_HDCP_H

> +#define _LINUX_MEI_HDCP_H

> +

> +enum mei_cldev_state {

> +	MEI_CLDEV_DISABLED,

> +	MEI_CLDEV_ENABLED

> +};

> +

> +#ifdef CONFIG_INTEL_MEI_HDCP

> +int mei_cldev_register_notify(struct notifier_block *nb);

> +int mei_cldev_unregister_notify(struct notifier_block *nb);

> +#else

> +static int mei_cldev_register_notify(struct notifier_block *nb)

> +{

> +	return -ENODEV;

> +}

> +static int mei_cldev_unregister_notify(struct notifier_block *nb)

> +{

> +	return -ENODEV;

> +}

> +#endif /* defined (CONFIG_INTEL_MEI_HDCP) */

> +#endif /* defined (_LINUX_MEI_HDCP_H) */

> --

> 2.7.4

Ramalingam C May 16, 2018, 1:04 p.m. UTC | #4

Thanks Alexander for the review. Sorry for the delay in addressing the 
review comments


On Wednesday 04 April 2018 11:42 AM, Usyskin, Alexander wrote:
>> -----Original Message-----
>> From: C, Ramalingam
>> Sent: Tuesday, April 03, 2018 16:57
>> To: [e-mail]; [e-mail];
>> [e-mail]; [e-mail]; [e-mail];
>> [e-mail]; Winkler, Tomas <[e-mail]>;
>> Usyskin, Alexander <[e-mail]>
>> Cc: Vivi, Rodrigo <[e-mail]>; C, Ramalingam
>> <[e-mail]>
>> Subject: [PATCH v3 05/40] misc/mei/hdcp: Notifier chain for mei cldev state
>> change
>>
>> Notifier Chain is defined to inform all its clients about the mei
>> client device state change. Routine is defined for the clients to
>> register and unregister for the notification on state change.
>>
>> v2:
>>    Rebased.
>> v3:
>>    Notifier chain is adopted for cldev state update [Tomas]
>>
>> Signed-off-by: Ramalingam C <[e-mail]>
>> ---
> May be I miss something, but bus subsystem already has notifier chain. (BUS_NOTIFY_ADD_DEVICE etc.)
> We only ought to make mei_cl_bus_type available in header.
We need re notification incase of binding of the mei device happened 
well before the I915 init.
This is the case if I915 and MEI HDCP are build as modules and loaded in 
order.

So I prefer the separate notifier for mei_hdcp. Hope that is fine.

--Ram
>
>>   drivers/misc/mei/hdcp/mei_hdcp.c | 36 +++++++++++++++++++++++++++---
>>   include/linux/mei_hdcp.h         | 48
>> ++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 81 insertions(+), 3 deletions(-)
>>   create mode 100644 include/linux/mei_hdcp.h
>>
>> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c
>> b/drivers/misc/mei/hdcp/mei_hdcp.c
>> index b334615728a7..2811a25f8c57 100644
>> --- a/drivers/misc/mei/hdcp/mei_hdcp.c
>> +++ b/drivers/misc/mei/hdcp/mei_hdcp.c
>> @@ -31,6 +31,32 @@
>>   #include <linux/slab.h>
>>   #include <linux/uuid.h>
>>   #include <linux/mei_cl_bus.h>
>> +#include <linux/notifier.h>
>> +#include <linux/mei_hdcp.h>
>> +
>> +static BLOCKING_NOTIFIER_HEAD(mei_cldev_notifier_list);
>> +
>> +void mei_cldev_state_notify_clients(struct mei_cl_device *cldev, bool
>> enabled)
>> +{
>> +	if (enabled)
>> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,
>> +					     MEI_CLDEV_ENABLED, cldev);
>> +	else
>> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,
>> +					     MEI_CLDEV_DISABLED, NULL);
>> +}
>> +
>> +int mei_cldev_register_notify(struct notifier_block *nb)
>> +{
>> +	return blocking_notifier_chain_register(&mei_cldev_notifier_list,
>> nb);
>> +}
>> +EXPORT_SYMBOL_GPL(mei_cldev_register_notify);
>> +
>> +int mei_cldev_unregister_notify(struct notifier_block *nb)
>> +{
>> +	return blocking_notifier_chain_unregister(&mei_cldev_notifier_list,
>> nb);
>> +}
>> +EXPORT_SYMBOL_GPL(mei_cldev_unregister_notify);
>>
>>   static int mei_hdcp_probe(struct mei_cl_device *cldev,
>>   			  const struct mei_cl_device_id *id)
>> @@ -38,14 +64,18 @@ static int mei_hdcp_probe(struct mei_cl_device
>> *cldev,
>>   	int ret;
>>
>>   	ret = mei_cldev_enable(cldev);
>> -	if (ret < 0)
>> +	if (ret < 0) {
>>   		dev_err(&cldev->dev, "mei_cldev_enable Failed. %d\n", ret);
>> +		return ret;
>> +	}
>>
>> -	return ret;
>> +	mei_cldev_state_notify_clients(cldev, true);
>> +	return 0;
>>   }
>>
>>   static int mei_hdcp_remove(struct mei_cl_device *cldev)
>>   {
>> +	mei_cldev_state_notify_clients(cldev, false);
>>   	mei_cldev_set_drvdata(cldev, NULL);
>>   	return mei_cldev_disable(cldev);
>>   }
>> @@ -71,4 +101,4 @@ module_mei_cl_driver(mei_hdcp_driver);
>>
>>   MODULE_AUTHOR("Intel Corporation");
>>   MODULE_LICENSE("Dual BSD/GPL");
>> -MODULE_DESCRIPTION("HDCP");
>> +MODULE_DESCRIPTION("MEI HDCP");
>> diff --git a/include/linux/mei_hdcp.h b/include/linux/mei_hdcp.h
>> new file mode 100644
>> index 000000000000..3b46bebde718
>> --- /dev/null
>> +++ b/include/linux/mei_hdcp.h
>> @@ -0,0 +1,48 @@
>> +/* SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause) */
>> +/*
>> + * Copyright © 2017-2018 Intel Corporation
>> + *
>> + * Permission to use, copy, modify, distribute, and sell this software and its
>> + * documentation for any purpose is hereby granted without fee, provided
>> that
>> + * the above copyright notice appear in all copies and that both that
>> copyright
>> + * notice and this permission notice appear in supporting documentation,
>> and
>> + * that the name of the copyright holders not be used in advertising or
>> + * publicity pertaining to distribution of the software without specific,
>> + * written prior permission.  The copyright holders make no representations
>> + * about the suitability of this software for any purpose.  It is provided "as
>> + * is" without express or implied warranty.
>> + *
>> + * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO
>> THIS SOFTWARE,
>> + * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
>> FITNESS, IN NO
>> + * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL,
>> INDIRECT OR
>> + * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
>> FROM LOSS OF USE,
>> + * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
>> OR OTHER
>> + * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE
>> OR PERFORMANCE
>> + * OF THIS SOFTWARE.
>> + *
>> + * Authors:
>> + *	Ramalingam C <[e-mail]>
>> + */
>> +
>> +#ifndef _LINUX_MEI_HDCP_H
>> +#define _LINUX_MEI_HDCP_H
>> +
>> +enum mei_cldev_state {
>> +	MEI_CLDEV_DISABLED,
>> +	MEI_CLDEV_ENABLED
>> +};
>> +
>> +#ifdef CONFIG_INTEL_MEI_HDCP
>> +int mei_cldev_register_notify(struct notifier_block *nb);
>> +int mei_cldev_unregister_notify(struct notifier_block *nb);
>> +#else
>> +static int mei_cldev_register_notify(struct notifier_block *nb)
>> +{
>> +	return -ENODEV;
>> +}
>> +static int mei_cldev_unregister_notify(struct notifier_block *nb)
>> +{
>> +	return -ENODEV;
>> +}
>> +#endif /* defined (CONFIG_INTEL_MEI_HDCP) */
>> +#endif /* defined (_LINUX_MEI_HDCP_H) */
>> --
>> 2.7.4

Ramalingam C May 16, 2018, 2:54 p.m. UTC | #5

On Tuesday 03 April 2018 09:00 PM, Daniel Vetter wrote:
> On Tue, Apr 03, 2018 at 07:27:18PM +0530, Ramalingam C wrote:
>> Notifier Chain is defined to inform all its clients about the mei
>> client device state change. Routine is defined for the clients to
>> register and unregister for the notification on state change.
>>
>> v2:
>>    Rebased.
>> v3:
>>    Notifier chain is adopted for cldev state update [Tomas]
>>
>> Signed-off-by: Ramalingam C <[e-mail]>
> For managing interactions between multiple drivers notifier chains are
> fairly problematic. The main reason is the locking embedded in the
> notifier chain. To make things safe, that lock must be held everytime we
> add/remove any part of the link, and when calling any callback. Usually
> that means you get a neat deadlock sooner or later, because the
> load/unload code has inverse paths compared to normal operation.
>
> Notifiers also not not provide a clean way to handle suspend/resume
> ordering.
Recording the IRC discussion here:

As Daniel Vetter suggested, with notifiers to mei client device binding 
status, I have tested
the I915 and mei_hdcp modules as inbuild and as modules at suspend and 
resume of them.

During the experiment, CONFIG_PROVE_LOCKING was enabled. No issue was 
observed due to the
usecase of the notifier here. Notifier was used here just to inform the 
I915 that mei client device is no more.
So that I915 will stop any ongoing HDCP2.2 protection and reject any 
further request.

Hence Planning to continue with same shape of the patch on v4. If any 
erroneous scenario is detected
we will work on the alternate solution.

--Ram
>
> There's two parts to do this properly.
>
> 1. Finding the other driver. Multi-part drivers are assembled nowadays
> using the component framework. We're using that already to manage the
> interaction between drm/i915 and snd-hda. If not all components are ready
> yet, then the driver load sequence must be aborted by returning
> -EPROBE_DEFER. That's going to be lots of fun, since for the mei/i915
> interaction it's probably going to be i915 that needs to abort and retry
> the driver load. But we do CI test all the abort points in our driver
> load, so should work well.
>
> 2. Handling the ordering restrictions for suspend/resume. For i915/snd-hda
> we used a early_resume/late_suspend callback trickery, but that doesn't
> really scale to multiple levels. Since we've done that device_link has
> been added. As a bonus device_link can also ensure that not only
> suspend/resume (including runtime suspend/resume) is ordered correctly,
> but also that driver bind/unbind works correctly. Still needs the
> component stuff and initial -EPROBE_DEFER, but will all least make sure
> we' only reprobe once more. See device_link_add + docs in device_link.rst.
>
> One thing I didn't check is whether we want the device linke to also
> manage runtime pm for us. It would mean that we keep the ME awake as long
> as anything is using the gpu (any display on or any rendering happening).
> That might be too much, but could also be that it won't matter (and then
> using DL_FLAG_PM_RUNTIME would simply our code).
>
> We might also need to convert the i915/snd-hda interactions to device_link
> first, since the early/late_resume/suspend hack probably doesn't interact
> too well with proper device_links.
>
> Cheers, Daniel
>
>> ---
>>   drivers/misc/mei/hdcp/mei_hdcp.c | 36 +++++++++++++++++++++++++++---
>>   include/linux/mei_hdcp.h         | 48 ++++++++++++++++++++++++++++++++++++++++
>>   2 files changed, 81 insertions(+), 3 deletions(-)
>>   create mode 100644 include/linux/mei_hdcp.h
>>
>> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c b/drivers/misc/mei/hdcp/mei_hdcp.c
>> index b334615728a7..2811a25f8c57 100644
>> --- a/drivers/misc/mei/hdcp/mei_hdcp.c
>> +++ b/drivers/misc/mei/hdcp/mei_hdcp.c
>> @@ -31,6 +31,32 @@
>>   #include <linux/slab.h>
>>   #include <linux/uuid.h>
>>   #include <linux/mei_cl_bus.h>
>> +#include <linux/notifier.h>
>> +#include <linux/mei_hdcp.h>
>> +
>> +static BLOCKING_NOTIFIER_HEAD(mei_cldev_notifier_list);
>> +
>> +void mei_cldev_state_notify_clients(struct mei_cl_device *cldev, bool enabled)
>> +{
>> +	if (enabled)
>> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,
>> +					     MEI_CLDEV_ENABLED, cldev);
>> +	else
>> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,
>> +					     MEI_CLDEV_DISABLED, NULL);
>> +}
>> +
>> +int mei_cldev_register_notify(struct notifier_block *nb)
>> +{
>> +	return blocking_notifier_chain_register(&mei_cldev_notifier_list, nb);
>> +}
>> +EXPORT_SYMBOL_GPL(mei_cldev_register_notify);
>> +
>> +int mei_cldev_unregister_notify(struct notifier_block *nb)
>> +{
>> +	return blocking_notifier_chain_unregister(&mei_cldev_notifier_list, nb);
>> +}
>> +EXPORT_SYMBOL_GPL(mei_cldev_unregister_notify);
>>   
>>   static int mei_hdcp_probe(struct mei_cl_device *cldev,
>>   			  const struct mei_cl_device_id *id)
>> @@ -38,14 +64,18 @@ static int mei_hdcp_probe(struct mei_cl_device *cldev,
>>   	int ret;
>>   
>>   	ret = mei_cldev_enable(cldev);
>> -	if (ret < 0)
>> +	if (ret < 0) {
>>   		dev_err(&cldev->dev, "mei_cldev_enable Failed. %d\n", ret);
>> +		return ret;
>> +	}
>>   
>> -	return ret;
>> +	mei_cldev_state_notify_clients(cldev, true);
>> +	return 0;
>>   }
>>   
>>   static int mei_hdcp_remove(struct mei_cl_device *cldev)
>>   {
>> +	mei_cldev_state_notify_clients(cldev, false);
>>   	mei_cldev_set_drvdata(cldev, NULL);
>>   	return mei_cldev_disable(cldev);
>>   }
>> @@ -71,4 +101,4 @@ module_mei_cl_driver(mei_hdcp_driver);
>>   
>>   MODULE_AUTHOR("Intel Corporation");
>>   MODULE_LICENSE("Dual BSD/GPL");
>> -MODULE_DESCRIPTION("HDCP");
>> +MODULE_DESCRIPTION("MEI HDCP");
>> diff --git a/include/linux/mei_hdcp.h b/include/linux/mei_hdcp.h
>> new file mode 100644
>> index 000000000000..3b46bebde718
>> --- /dev/null
>> +++ b/include/linux/mei_hdcp.h
>> @@ -0,0 +1,48 @@
>> +/* SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause) */
>> +/*
>> + * Copyright © 2017-2018 Intel Corporation
>> + *
>> + * Permission to use, copy, modify, distribute, and sell this software and its
>> + * documentation for any purpose is hereby granted without fee, provided that
>> + * the above copyright notice appear in all copies and that both that copyright
>> + * notice and this permission notice appear in supporting documentation, and
>> + * that the name of the copyright holders not be used in advertising or
>> + * publicity pertaining to distribution of the software without specific,
>> + * written prior permission.  The copyright holders make no representations
>> + * about the suitability of this software for any purpose.  It is provided "as
>> + * is" without express or implied warranty.
>> + *
>> + * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
>> + * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
>> + * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
>> + * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
>> + * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
>> + * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
>> + * OF THIS SOFTWARE.
>> + *
>> + * Authors:
>> + *	Ramalingam C <[e-mail]>
>> + */
>> +
>> +#ifndef _LINUX_MEI_HDCP_H
>> +#define _LINUX_MEI_HDCP_H
>> +
>> +enum mei_cldev_state {
>> +	MEI_CLDEV_DISABLED,
>> +	MEI_CLDEV_ENABLED
>> +};
>> +
>> +#ifdef CONFIG_INTEL_MEI_HDCP
>> +int mei_cldev_register_notify(struct notifier_block *nb);
>> +int mei_cldev_unregister_notify(struct notifier_block *nb);
>> +#else
>> +static int mei_cldev_register_notify(struct notifier_block *nb)
>> +{
>> +	return -ENODEV;
>> +}
>> +static int mei_cldev_unregister_notify(struct notifier_block *nb)
>> +{
>> +	return -ENODEV;
>> +}
>> +#endif /* defined (CONFIG_INTEL_MEI_HDCP) */
>> +#endif /* defined (_LINUX_MEI_HDCP_H) */
>> -- 
>> 2.7.4
>>

Alexander Usyskin May 17, 2018, 5:52 a.m. UTC | #6

> -----Original Message-----

> From: C, Ramalingam

> Sent: Wednesday, May 16, 2018 16:05

> To: Usyskin, Alexander <[e-mail]>; intel-

> [e-mail]; [e-mail];

> [e-mail]; [e-mail]; [e-mail];

> [e-mail]; Winkler, Tomas <[e-mail]>

> Cc: Vivi, Rodrigo <[e-mail]>

> Subject: Re: [PATCH v3 05/40] misc/mei/hdcp: Notifier chain for mei cldev

> state change

> 

> Thanks Alexander for the review. Sorry for the delay in addressing the review

> comments

> 

> 

> On Wednesday 04 April 2018 11:42 AM, Usyskin, Alexander wrote:

> >> -----Original Message-----

> >> From: C, Ramalingam

> >> Sent: Tuesday, April 03, 2018 16:57

> >> To: [e-mail]; [e-mail];

> >> [e-mail]; [e-mail]; [e-mail];

> >> [e-mail]; Winkler, Tomas <[e-mail]>;

> >> Usyskin, Alexander <[e-mail]>

> >> Cc: Vivi, Rodrigo <[e-mail]>; C, Ramalingam

> >> <[e-mail]>

> >> Subject: [PATCH v3 05/40] misc/mei/hdcp: Notifier chain for mei cldev

> state

> >> change

> >>

> >> Notifier Chain is defined to inform all its clients about the mei

> >> client device state change. Routine is defined for the clients to

> >> register and unregister for the notification on state change.

> >>

> >> v2:

> >>    Rebased.

> >> v3:

> >>    Notifier chain is adopted for cldev state update [Tomas]

> >>

> >> Signed-off-by: Ramalingam C <[e-mail]>

> >> ---

> > May be I miss something, but bus subsystem already has notifier chain.

> (BUS_NOTIFY_ADD_DEVICE etc.)

> > We only ought to make mei_cl_bus_type available in header.

> We need re notification incase of binding of the mei device happened

> well before the I915 init.

> This is the case if I915 and MEI HDCP are build as modules and loaded in

> order.

> 

> So I prefer the separate notifier for mei_hdcp. Hope that is fine.

> 

> --Ram


Still miss the part how you design coupe with mei device loaded well before i915?
Can you explain?

> >

> >>   drivers/misc/mei/hdcp/mei_hdcp.c | 36

> +++++++++++++++++++++++++++---

> >>   include/linux/mei_hdcp.h         | 48

> >> ++++++++++++++++++++++++++++++++++++++++

> >>   2 files changed, 81 insertions(+), 3 deletions(-)

> >>   create mode 100644 include/linux/mei_hdcp.h

> >>

> >> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c

> >> b/drivers/misc/mei/hdcp/mei_hdcp.c

> >> index b334615728a7..2811a25f8c57 100644

> >> --- a/drivers/misc/mei/hdcp/mei_hdcp.c

> >> +++ b/drivers/misc/mei/hdcp/mei_hdcp.c

> >> @@ -31,6 +31,32 @@

> >>   #include <linux/slab.h>

> >>   #include <linux/uuid.h>

> >>   #include <linux/mei_cl_bus.h>

> >> +#include <linux/notifier.h>

> >> +#include <linux/mei_hdcp.h>

> >> +

> >> +static BLOCKING_NOTIFIER_HEAD(mei_cldev_notifier_list);

> >> +

> >> +void mei_cldev_state_notify_clients(struct mei_cl_device *cldev, bool

> >> enabled)

> >> +{

> >> +	if (enabled)

> >> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,

> >> +					     MEI_CLDEV_ENABLED, cldev);

> >> +	else

> >> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,

> >> +					     MEI_CLDEV_DISABLED, NULL);

> >> +}

> >> +

> >> +int mei_cldev_register_notify(struct notifier_block *nb)

> >> +{

> >> +	return blocking_notifier_chain_register(&mei_cldev_notifier_list,

> >> nb);

> >> +}

> >> +EXPORT_SYMBOL_GPL(mei_cldev_register_notify);

> >> +

> >> +int mei_cldev_unregister_notify(struct notifier_block *nb)

> >> +{

> >> +	return blocking_notifier_chain_unregister(&mei_cldev_notifier_list,

> >> nb);

> >> +}

> >> +EXPORT_SYMBOL_GPL(mei_cldev_unregister_notify);

> >>

> >>   static int mei_hdcp_probe(struct mei_cl_device *cldev,

> >>   			  const struct mei_cl_device_id *id)

> >> @@ -38,14 +64,18 @@ static int mei_hdcp_probe(struct mei_cl_device

> >> *cldev,

> >>   	int ret;

> >>

> >>   	ret = mei_cldev_enable(cldev);

> >> -	if (ret < 0)

> >> +	if (ret < 0) {

> >>   		dev_err(&cldev->dev, "mei_cldev_enable Failed. %d\n", ret);

> >> +		return ret;

> >> +	}

> >>

> >> -	return ret;

> >> +	mei_cldev_state_notify_clients(cldev, true);

> >> +	return 0;

> >>   }

> >>

> >>   static int mei_hdcp_remove(struct mei_cl_device *cldev)

> >>   {

> >> +	mei_cldev_state_notify_clients(cldev, false);

> >>   	mei_cldev_set_drvdata(cldev, NULL);

> >>   	return mei_cldev_disable(cldev);

> >>   }

> >> @@ -71,4 +101,4 @@ module_mei_cl_driver(mei_hdcp_driver);

> >>

> >>   MODULE_AUTHOR("Intel Corporation");

> >>   MODULE_LICENSE("Dual BSD/GPL");

> >> -MODULE_DESCRIPTION("HDCP");

> >> +MODULE_DESCRIPTION("MEI HDCP");

> >> diff --git a/include/linux/mei_hdcp.h b/include/linux/mei_hdcp.h

> >> new file mode 100644

> >> index 000000000000..3b46bebde718

> >> --- /dev/null

> >> +++ b/include/linux/mei_hdcp.h

> >> @@ -0,0 +1,48 @@

> >> +/* SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause) */

> >> +/*

> >> + * Copyright © 2017-2018 Intel Corporation

> >> + *

> >> + * Permission to use, copy, modify, distribute, and sell this software and

> its

> >> + * documentation for any purpose is hereby granted without fee,

> provided

> >> that

> >> + * the above copyright notice appear in all copies and that both that

> >> copyright

> >> + * notice and this permission notice appear in supporting

> documentation,

> >> and

> >> + * that the name of the copyright holders not be used in advertising or

> >> + * publicity pertaining to distribution of the software without specific,

> >> + * written prior permission.  The copyright holders make no

> representations

> >> + * about the suitability of this software for any purpose.  It is provided

> "as

> >> + * is" without express or implied warranty.

> >> + *

> >> + * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD

> TO

> >> THIS SOFTWARE,

> >> + * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND

> >> FITNESS, IN NO

> >> + * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL,

> >> INDIRECT OR

> >> + * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER

> RESULTING

> >> FROM LOSS OF USE,

> >> + * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,

> NEGLIGENCE

> >> OR OTHER

> >> + * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE

> USE

> >> OR PERFORMANCE

> >> + * OF THIS SOFTWARE.

> >> + *

> >> + * Authors:

> >> + *	Ramalingam C <[e-mail]>

> >> + */

> >> +

> >> +#ifndef _LINUX_MEI_HDCP_H

> >> +#define _LINUX_MEI_HDCP_H

> >> +

> >> +enum mei_cldev_state {

> >> +	MEI_CLDEV_DISABLED,

> >> +	MEI_CLDEV_ENABLED

> >> +};

> >> +

> >> +#ifdef CONFIG_INTEL_MEI_HDCP

> >> +int mei_cldev_register_notify(struct notifier_block *nb);

> >> +int mei_cldev_unregister_notify(struct notifier_block *nb);

> >> +#else

> >> +static int mei_cldev_register_notify(struct notifier_block *nb)

> >> +{

> >> +	return -ENODEV;

> >> +}

> >> +static int mei_cldev_unregister_notify(struct notifier_block *nb)

> >> +{

> >> +	return -ENODEV;

> >> +}

> >> +#endif /* defined (CONFIG_INTEL_MEI_HDCP) */

> >> +#endif /* defined (_LINUX_MEI_HDCP_H) */

> >> --

> >> 2.7.4

Ramalingam C May 17, 2018, 6:15 a.m. UTC | #7

On Thursday 17 May 2018 11:22 AM, Usyskin, Alexander wrote:
>
>> -----Original Message-----
>> From: C, Ramalingam
>> Sent: Wednesday, May 16, 2018 16:05
>> To: Usyskin, Alexander <[e-mail]>; intel-
>> [e-mail]; [e-mail];
>> [e-mail]; [e-mail]; [e-mail];
>> [e-mail]; Winkler, Tomas <[e-mail]>
>> Cc: Vivi, Rodrigo <[e-mail]>
>> Subject: Re: [PATCH v3 05/40] misc/mei/hdcp: Notifier chain for mei cldev
>> state change
>>
>> Thanks Alexander for the review. Sorry for the delay in addressing the review
>> comments
>>
>>
>> On Wednesday 04 April 2018 11:42 AM, Usyskin, Alexander wrote:
>>>> -----Original Message-----
>>>> From: C, Ramalingam
>>>> Sent: Tuesday, April 03, 2018 16:57
>>>> To: [e-mail]; [e-mail];
>>>> [e-mail]; [e-mail]; [e-mail];
>>>> [e-mail]; Winkler, Tomas <[e-mail]>;
>>>> Usyskin, Alexander <[e-mail]>
>>>> Cc: Vivi, Rodrigo <[e-mail]>; C, Ramalingam
>>>> <[e-mail]>
>>>> Subject: [PATCH v3 05/40] misc/mei/hdcp: Notifier chain for mei cldev
>> state
>>>> change
>>>>
>>>> Notifier Chain is defined to inform all its clients about the mei
>>>> client device state change. Routine is defined for the clients to
>>>> register and unregister for the notification on state change.
>>>>
>>>> v2:
>>>>     Rebased.
>>>> v3:
>>>>     Notifier chain is adopted for cldev state update [Tomas]
>>>>
>>>> Signed-off-by: Ramalingam C <[e-mail]>
>>>> ---
>>> May be I miss something, but bus subsystem already has notifier chain.
>> (BUS_NOTIFY_ADD_DEVICE etc.)
>>> We only ought to make mei_cl_bus_type available in header.
>> We need re notification incase of binding of the mei device happened
>> well before the I915 init.
>> This is the case if I915 and MEI HDCP are build as modules and loaded in
>> order.
>>
>> So I prefer the separate notifier for mei_hdcp. Hope that is fine.
>>
>> --Ram
> Still miss the part how you design coupe with mei device loaded well before i915?
> Can you explain?

If you build both I915 and mei_hdcp as modules, as mei_hdcp provides 
some symbols for the I915, mei_hdcp needs to be loaded first.
Hence mei hdcp client device binding is completed before the I915 Load. 
So notifier triggered even before its listener I915 is ready.
So When you load the I915 after mei hdcp client device binding, We need 
to trigger the notifier calls once again, so that I915 will get the 
handle cldev.


--Ram
>
>>>>    drivers/misc/mei/hdcp/mei_hdcp.c | 36
>> +++++++++++++++++++++++++++---
>>>>    include/linux/mei_hdcp.h         | 48
>>>> ++++++++++++++++++++++++++++++++++++++++
>>>>    2 files changed, 81 insertions(+), 3 deletions(-)
>>>>    create mode 100644 include/linux/mei_hdcp.h
>>>>
>>>> diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c
>>>> b/drivers/misc/mei/hdcp/mei_hdcp.c
>>>> index b334615728a7..2811a25f8c57 100644
>>>> --- a/drivers/misc/mei/hdcp/mei_hdcp.c
>>>> +++ b/drivers/misc/mei/hdcp/mei_hdcp.c
>>>> @@ -31,6 +31,32 @@
>>>>    #include <linux/slab.h>
>>>>    #include <linux/uuid.h>
>>>>    #include <linux/mei_cl_bus.h>
>>>> +#include <linux/notifier.h>
>>>> +#include <linux/mei_hdcp.h>
>>>> +
>>>> +static BLOCKING_NOTIFIER_HEAD(mei_cldev_notifier_list);
>>>> +
>>>> +void mei_cldev_state_notify_clients(struct mei_cl_device *cldev, bool
>>>> enabled)
>>>> +{
>>>> +	if (enabled)
>>>> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,
>>>> +					     MEI_CLDEV_ENABLED, cldev);
>>>> +	else
>>>> +		blocking_notifier_call_chain(&mei_cldev_notifier_list,
>>>> +					     MEI_CLDEV_DISABLED, NULL);
>>>> +}
>>>> +
>>>> +int mei_cldev_register_notify(struct notifier_block *nb)
>>>> +{
>>>> +	return blocking_notifier_chain_register(&mei_cldev_notifier_list,
>>>> nb);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(mei_cldev_register_notify);
>>>> +
>>>> +int mei_cldev_unregister_notify(struct notifier_block *nb)
>>>> +{
>>>> +	return blocking_notifier_chain_unregister(&mei_cldev_notifier_list,
>>>> nb);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(mei_cldev_unregister_notify);
>>>>
>>>>    static int mei_hdcp_probe(struct mei_cl_device *cldev,
>>>>    			  const struct mei_cl_device_id *id)
>>>> @@ -38,14 +64,18 @@ static int mei_hdcp_probe(struct mei_cl_device
>>>> *cldev,
>>>>    	int ret;
>>>>
>>>>    	ret = mei_cldev_enable(cldev);
>>>> -	if (ret < 0)
>>>> +	if (ret < 0) {
>>>>    		dev_err(&cldev->dev, "mei_cldev_enable Failed. %d\n", ret);
>>>> +		return ret;
>>>> +	}
>>>>
>>>> -	return ret;
>>>> +	mei_cldev_state_notify_clients(cldev, true);
>>>> +	return 0;
>>>>    }
>>>>
>>>>    static int mei_hdcp_remove(struct mei_cl_device *cldev)
>>>>    {
>>>> +	mei_cldev_state_notify_clients(cldev, false);
>>>>    	mei_cldev_set_drvdata(cldev, NULL);
>>>>    	return mei_cldev_disable(cldev);
>>>>    }
>>>> @@ -71,4 +101,4 @@ module_mei_cl_driver(mei_hdcp_driver);
>>>>
>>>>    MODULE_AUTHOR("Intel Corporation");
>>>>    MODULE_LICENSE("Dual BSD/GPL");
>>>> -MODULE_DESCRIPTION("HDCP");
>>>> +MODULE_DESCRIPTION("MEI HDCP");
>>>> diff --git a/include/linux/mei_hdcp.h b/include/linux/mei_hdcp.h
>>>> new file mode 100644
>>>> index 000000000000..3b46bebde718
>>>> --- /dev/null
>>>> +++ b/include/linux/mei_hdcp.h
>>>> @@ -0,0 +1,48 @@
>>>> +/* SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause) */
>>>> +/*
>>>> + * Copyright © 2017-2018 Intel Corporation
>>>> + *
>>>> + * Permission to use, copy, modify, distribute, and sell this software and
>> its
>>>> + * documentation for any purpose is hereby granted without fee,
>> provided
>>>> that
>>>> + * the above copyright notice appear in all copies and that both that
>>>> copyright
>>>> + * notice and this permission notice appear in supporting
>> documentation,
>>>> and
>>>> + * that the name of the copyright holders not be used in advertising or
>>>> + * publicity pertaining to distribution of the software without specific,
>>>> + * written prior permission.  The copyright holders make no
>> representations
>>>> + * about the suitability of this software for any purpose.  It is provided
>> "as
>>>> + * is" without express or implied warranty.
>>>> + *
>>>> + * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD
>> TO
>>>> THIS SOFTWARE,
>>>> + * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
>>>> FITNESS, IN NO
>>>> + * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL,
>>>> INDIRECT OR
>>>> + * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
>> RESULTING
>>>> FROM LOSS OF USE,
>>>> + * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
>> NEGLIGENCE
>>>> OR OTHER
>>>> + * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE
>> USE
>>>> OR PERFORMANCE
>>>> + * OF THIS SOFTWARE.
>>>> + *
>>>> + * Authors:
>>>> + *	Ramalingam C <[e-mail]>
>>>> + */
>>>> +
>>>> +#ifndef _LINUX_MEI_HDCP_H
>>>> +#define _LINUX_MEI_HDCP_H
>>>> +
>>>> +enum mei_cldev_state {
>>>> +	MEI_CLDEV_DISABLED,
>>>> +	MEI_CLDEV_ENABLED
>>>> +};
>>>> +
>>>> +#ifdef CONFIG_INTEL_MEI_HDCP
>>>> +int mei_cldev_register_notify(struct notifier_block *nb);
>>>> +int mei_cldev_unregister_notify(struct notifier_block *nb);
>>>> +#else
>>>> +static int mei_cldev_register_notify(struct notifier_block *nb)
>>>> +{
>>>> +	return -ENODEV;
>>>> +}
>>>> +static int mei_cldev_unregister_notify(struct notifier_block *nb)
>>>> +{
>>>> +	return -ENODEV;
>>>> +}
>>>> +#endif /* defined (CONFIG_INTEL_MEI_HDCP) */
>>>> +#endif /* defined (_LINUX_MEI_HDCP_H) */
>>>> --
>>>> 2.7.4

Patch

diff --git a/drivers/misc/mei/hdcp/mei_hdcp.c b/drivers/misc/mei/hdcp/mei_hdcp.c
index b334615728a7..2811a25f8c57 100644
--- a/drivers/misc/mei/hdcp/mei_hdcp.c
+++ b/drivers/misc/mei/hdcp/mei_hdcp.c
@@ -31,6 +31,32 @@ 
 #include <linux/slab.h>
 #include <linux/uuid.h>
 #include <linux/mei_cl_bus.h>
+#include <linux/notifier.h>
+#include <linux/mei_hdcp.h>
+
+static BLOCKING_NOTIFIER_HEAD(mei_cldev_notifier_list);
+
+void mei_cldev_state_notify_clients(struct mei_cl_device *cldev, bool enabled)
+{
+	if (enabled)
+		blocking_notifier_call_chain(&mei_cldev_notifier_list,
+					     MEI_CLDEV_ENABLED, cldev);
+	else
+		blocking_notifier_call_chain(&mei_cldev_notifier_list,
+					     MEI_CLDEV_DISABLED, NULL);
+}
+
+int mei_cldev_register_notify(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_register(&mei_cldev_notifier_list, nb);
+}
+EXPORT_SYMBOL_GPL(mei_cldev_register_notify);
+
+int mei_cldev_unregister_notify(struct notifier_block *nb)
+{
+	return blocking_notifier_chain_unregister(&mei_cldev_notifier_list, nb);
+}
+EXPORT_SYMBOL_GPL(mei_cldev_unregister_notify);
 
 static int mei_hdcp_probe(struct mei_cl_device *cldev,
 			  const struct mei_cl_device_id *id)
@@ -38,14 +64,18 @@  static int mei_hdcp_probe(struct mei_cl_device *cldev,
 	int ret;
 
 	ret = mei_cldev_enable(cldev);
-	if (ret < 0)
+	if (ret < 0) {
 		dev_err(&cldev->dev, "mei_cldev_enable Failed. %d\n", ret);
+		return ret;
+	}
 
-	return ret;
+	mei_cldev_state_notify_clients(cldev, true);
+	return 0;
 }
 
 static int mei_hdcp_remove(struct mei_cl_device *cldev)
 {
+	mei_cldev_state_notify_clients(cldev, false);
 	mei_cldev_set_drvdata(cldev, NULL);
 	return mei_cldev_disable(cldev);
 }
@@ -71,4 +101,4 @@  module_mei_cl_driver(mei_hdcp_driver);
 
 MODULE_AUTHOR("Intel Corporation");
 MODULE_LICENSE("Dual BSD/GPL");
-MODULE_DESCRIPTION("HDCP");
+MODULE_DESCRIPTION("MEI HDCP");
diff --git a/include/linux/mei_hdcp.h b/include/linux/mei_hdcp.h
new file mode 100644
index 000000000000..3b46bebde718
--- /dev/null
+++ b/include/linux/mei_hdcp.h
@@ -0,0 +1,48 @@ 
+/* SPDX-License-Identifier: (GPL-2.0+ OR BSD-3-Clause) */
+/*
+ * Copyright © 2017-2018 Intel Corporation
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ *
+ * Authors:
+ *	Ramalingam C <[e-mail]>
+ */
+
+#ifndef _LINUX_MEI_HDCP_H
+#define _LINUX_MEI_HDCP_H
+
+enum mei_cldev_state {
+	MEI_CLDEV_DISABLED,
+	MEI_CLDEV_ENABLED
+};
+
+#ifdef CONFIG_INTEL_MEI_HDCP
+int mei_cldev_register_notify(struct notifier_block *nb);
+int mei_cldev_unregister_notify(struct notifier_block *nb);
+#else
+static int mei_cldev_register_notify(struct notifier_block *nb)
+{
+	return -ENODEV;
+}
+static int mei_cldev_unregister_notify(struct notifier_block *nb)
+{
+	return -ENODEV;
+}
+#endif /* defined (CONFIG_INTEL_MEI_HDCP) */
+#endif /* defined (_LINUX_MEI_HDCP_H) */