| Message ID | e71c63c2f61135f9a8c7884525aab2c48f1e84c2.1740993491.git.mazziesaccount@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Geert Uytterhoeven |
| Headers | show |
| Series | Support ROHM BD79124 ADC | expand |
On Mon, Mar 3, 2025 at 12:32 PM Matti Vaittinen <mazziesaccount@gmail.com> wrote: > > There are ADC ICs which may have some of the AIN pins usable for other > functions. These ICs may have some of the AIN pins wired so that they > should not be used for ADC. > > (Preferred?) way for marking pins which can be used as ADC inputs is to > add corresponding channels@N nodes in the device tree as described in > the ADC binding yaml. > > Add couple of helper functions which can be used to retrieve the channel > information from the device node. > > Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com> > > --- > Revision history: > v4 => v5: > - Inline iio_adc_device_num_channels() > - Fix Indenting function parameters > - Combine the max channel ID checks. > v3 => v4: > - Drop diff-channel support > - Drop iio_adc_device_channels_by_property() > - Add IIO_DEVICE namespace > - Move industrialio-adc.o to top of the Makefile > - Some styling as suggested by Andy > - Re-consider included headers > v2 => v3: Mostly based on review comments by Jonathan > - Support differential and single-ended channels > - Rename iio_adc_device_get_channels() as > iio_adc_device_channels_by_property() > - Improve spelling > - Drop support for cases where DT comes from parent device's node > - Decrease loop indent by reverting node name check conditions > - Don't set 'chan->indexed' by number of channels to keep the > interface consistent no matter how many channels are connected. > - Fix ID range check and related comment > RFC v1 => v2: > - New patch > --- > drivers/iio/adc/Kconfig | 3 ++ > drivers/iio/adc/Makefile | 2 + > drivers/iio/adc/industrialio-adc.c | 82 ++++++++++++++++++++++++++++++ > include/linux/iio/adc-helpers.h | 27 ++++++++++ > 4 files changed, 114 insertions(+) > create mode 100644 drivers/iio/adc/industrialio-adc.c > create mode 100644 include/linux/iio/adc-helpers.h > > diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig > index 849c90203071..37b70a65da6f 100644 > --- a/drivers/iio/adc/Kconfig > +++ b/drivers/iio/adc/Kconfig > @@ -6,6 +6,9 @@ > > menu "Analog to digital converters" > > +config IIO_ADC_HELPER > + tristate > + > config AB8500_GPADC > bool "ST-Ericsson AB8500 GPADC driver" > depends on AB8500_CORE && REGULATOR_AB8500 > diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile > index ee19afba62b7..1c410f483029 100644 > --- a/drivers/iio/adc/Makefile > +++ b/drivers/iio/adc/Makefile > @@ -3,6 +3,8 @@ > # Makefile for IIO ADC drivers > # > > +obj-$(CONFIG_IIO_ADC_HELPER) += industrialio-adc.o > + > # When adding new entries keep the list in alphabetical order > obj-$(CONFIG_AB8500_GPADC) += ab8500-gpadc.o > obj-$(CONFIG_AD_SIGMA_DELTA) += ad_sigma_delta.o > diff --git a/drivers/iio/adc/industrialio-adc.c b/drivers/iio/adc/industrialio-adc.c > new file mode 100644 > index 000000000000..7bdae5330224 > --- /dev/null > +++ b/drivers/iio/adc/industrialio-adc.c > @@ -0,0 +1,82 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +/* > + * Helpers for parsing common ADC information from a firmware node. > + * > + * Copyright (c) 2025 Matti Vaittinen <mazziesaccount@gmail.com> > + */ > + > +#include <linux/device.h> > +#include <linux/errno.h> > +#include <linux/export.h> > +#include <linux/module.h> > +#include <linux/property.h> > +#include <linux/types.h> > + > +#include <linux/iio/adc-helpers.h> > +#include <linux/iio/iio.h> > + > +/** > + * devm_iio_adc_device_alloc_chaninfo_se - allocate and fill iio_chan_spec for ADC > + * > + * Scan the device node for single-ended ADC channel information. Channel ID is > + * expected to be found from the "reg" property. Allocate and populate the > + * iio_chan_spec structure corresponding to channels that are found. The memory > + * for iio_chan_spec structure will be freed upon device detach. > + * > + * @dev: Pointer to the ADC device. > + * @template: Template iio_chan_spec from which the fields of all > + * found and allocated channels are initialized. > + * @max_chan_id: Maximum value of a channel ID. Use -1 if no checking > + * is required. > + * @cs: Location where pointer to allocated iio_chan_spec > + * should be stored. > + * > + * Return: Number of found channels on succes. Negative value to indicate s/succes/success/ > + * failure. > + */ > +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, > + const struct iio_chan_spec *template, > + int max_chan_id, > + struct iio_chan_spec **cs) > +{ > + struct iio_chan_spec *chan_array, *chan; > + int num_chan = 0, ret; > + > + num_chan = iio_adc_device_num_channels(dev); > + if (num_chan < 1) > + return num_chan; > + > + chan_array = devm_kcalloc(dev, num_chan, sizeof(*chan_array), > + GFP_KERNEL); > + if (!chan_array) > + return -ENOMEM; > + > + chan = &chan_array[0]; > + > + device_for_each_child_node_scoped(dev, child) { > + u32 ch; > + > + if (!fwnode_name_eq(child, "channel")) > + continue; > + > + ret = fwnode_property_read_u32(child, "reg", &ch); > + if (ret) > + return ret; > + > + if (max_chan_id != -1 && ch > max_chan_id) > + return -ERANGE; > + Should we use return dev_err_probe() on these to help with debugging a bad dtb? > + *chan = *template; > + chan->channel = ch; > + chan++; > + } > + > + *cs = chan_array; > + > + return num_chan; > +} > +EXPORT_SYMBOL_NS_GPL(devm_iio_adc_device_alloc_chaninfo_se, "IIO_DRIVER"); We can make this less verbose by setting #define DEFAULT_SYMBOL_NAMESPACE at the start of the file. Then we can just do EXPORT_SYMBOL_GPL() throughout the rest of the file. Also, I would prefer if the namespace matched config name (IIO_ADC_HELPER). > + > +MODULE_LICENSE("GPL"); > +MODULE_AUTHOR("Matti Vaittinen <mazziesaccount@gmail.com>"); > +MODULE_DESCRIPTION("IIO ADC fwnode parsing helpers"); > diff --git a/include/linux/iio/adc-helpers.h b/include/linux/iio/adc-helpers.h > new file mode 100644 > index 000000000000..403a70b109ec > --- /dev/null > +++ b/include/linux/iio/adc-helpers.h > @@ -0,0 +1,27 @@ > +/* SPDX-License-Identifier: GPL-2.0-only */ > + > +/* > + * The industrial I/O ADC firmware property parsing helpers > + * > + * Copyright (c) 2025 Matti Vaittinen <mazziesaccount@gmail.com> > + */ > + > +#ifndef _INDUSTRIAL_IO_ADC_HELPERS_H_ > +#define _INDUSTRIAL_IO_ADC_HELPERS_H_ > + > +#include <linux/property.h> > + > +struct device; > +struct iio_chan_spec; > + > +static inline int iio_adc_device_num_channels(struct device *dev) > +{ > + return device_get_child_node_count_named(dev, "channel"); > +} > + > +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, > + const struct iio_chan_spec *template, > + int max_chan_id, > + struct iio_chan_spec **cs); > + There are some different opinions on this, but on the last patch I did introducing a new namespace, the consensus seems to be that putting the MODULE_IMPORT_NS() in the header file was convenient so that users of the API don't have to remember to both include the header and add the import macro. > +#endif /* _INDUSTRIAL_IO_ADC_HELPERS_H_ */ > -- > 2.48.1 >
On Tue, Mar 04, 2025 at 10:25:03AM +0100, David Lechner wrote: > On Mon, Mar 3, 2025 at 12:32 PM Matti Vaittinen > <mazziesaccount@gmail.com> wrote: ... > There are some different opinions on this, but on the last patch I did > introducing a new namespace, > the consensus Hmm... I may not call that "the consensus"... > seems to be that putting > the MODULE_IMPORT_NS() in the header file was convenient so that users > of the API don't have to remember to both include the header and add > the import macro. Which I am against because it will diminish the point of prevention of the APIs abuse along with a potential to have the stale headers in the file when the code is moved somewhere else.. So, please do not do that. We have only two abusers currently: the PWM and SPI OFFLOAD.
Thanks for the review David. On 04/03/2025 11:25, David Lechner wrote: > On Mon, Mar 3, 2025 at 12:32 PM Matti Vaittinen > <mazziesaccount@gmail.com> wrote: >> >> There are ADC ICs which may have some of the AIN pins usable for other >> functions. These ICs may have some of the AIN pins wired so that they >> should not be used for ADC. >> >> (Preferred?) way for marking pins which can be used as ADC inputs is to >> add corresponding channels@N nodes in the device tree as described in >> the ADC binding yaml. >> >> Add couple of helper functions which can be used to retrieve the channel >> information from the device node. >> >> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com> >> >> --- >> + * >> + * Return: Number of found channels on succes. Negative value to indicate > > s/succes/success/ Thanks! >> +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, >> + const struct iio_chan_spec *template, >> + int max_chan_id, >> + struct iio_chan_spec **cs) >> +{ >> + struct iio_chan_spec *chan_array, *chan; >> + int num_chan = 0, ret; >> + >> + num_chan = iio_adc_device_num_channels(dev); >> + if (num_chan < 1) >> + return num_chan; >> + >> + chan_array = devm_kcalloc(dev, num_chan, sizeof(*chan_array), >> + GFP_KERNEL); >> + if (!chan_array) >> + return -ENOMEM; >> + >> + chan = &chan_array[0]; >> + >> + device_for_each_child_node_scoped(dev, child) { >> + u32 ch; >> + >> + if (!fwnode_name_eq(child, "channel")) >> + continue; >> + >> + ret = fwnode_property_read_u32(child, "reg", &ch); >> + if (ret) >> + return ret; >> + >> + if (max_chan_id != -1 && ch > max_chan_id) >> + return -ERANGE; >> + > > Should we use return dev_err_probe() on these to help with debugging a bad dtb? > I am not fan of using dev_err_probe() in a 'library code'. This is because we never know if there'll be some odd use-case where this is not called from the probe. All in all, I'd leave adding most of the debugs to the callers - especially because we do not expect to have bad device-trees after the initial 'development stage' of a board. The board 'development stage' should really reveal bugs which prevent the channels from being registered - and after the DT is correct, these debug prints become unnecessary (albeit minor) binary bloat. >> + *chan = *template; >> + chan->channel = ch; >> + chan++; >> + } >> + >> + *cs = chan_array; >> + >> + return num_chan; >> +} >> +EXPORT_SYMBOL_NS_GPL(devm_iio_adc_device_alloc_chaninfo_se, "IIO_DRIVER"); > > We can make this less verbose by setting #define > DEFAULT_SYMBOL_NAMESPACE at the start of the file. Then we can just do > EXPORT_SYMBOL_GPL() throughout the rest of the file. I am not sure what to think of this. I use the good old 'ctrl + ]' in my editor when I need to check how a function was supposed to be used. That jumps to the spot of code where the function is. I'd like to see the namespace mentioned there in order to not accidentally miss the fact the function belongs to one. OTOH, I do like simplifications. Yet, the added simplification might not warrant the namespace not being visible in the function definition. > Also, I would prefer if the namespace matched config name (IIO_ADC_HELPER). I had some lengthy discussion about this with Andy and Jonathan during earlier review versions. In short, I don't like the idea of very fragmented namespaces in IIO, which will just complicate the drivers without providing any obvious benefit. https://lore.kernel.org/all/20250222174842.57c091c5@jic23-huawei/ >> + >> +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, >> + const struct iio_chan_spec *template, >> + int max_chan_id, >> + struct iio_chan_spec **cs); >> + > > There are some different opinions on this, but on the last patch I did > introducing a new namespace, the consensus seems to be that putting > the MODULE_IMPORT_NS() in the header file was convenient so that users > of the API don't have to remember to both include the header and add > the import macro. > I do like this suggestion, and I believe this would be the balance between getting the benefit of hiding part of the symbols - while not unnecessarily complicating the callers. I know some people are opposing it though. My personal opinion is that having the MODULE_IMPORT_NS() in a header would be neatly simplifying the calling code with very little harm, especially here where including the header hardly has use-cases outside the IIO ADC. Unfortunately, the "safety" seems to often be a synonym for just "making it intentionally hard". As Finnish people say: "Kärsi, kärsi, kirkkaamman kruunun saat". :) (Roughly translated as "Suffer, suffer, you will get a brighter crown"). Let's hear what Jonathan thinks of your suggestion. Thanks! -- Matti
On Wed, 5 Mar 2025 12:54:33 +0200 Matti Vaittinen <mazziesaccount@gmail.com> wrote: > Thanks for the review David. > > On 04/03/2025 11:25, David Lechner wrote: > > On Mon, Mar 3, 2025 at 12:32 PM Matti Vaittinen > > <mazziesaccount@gmail.com> wrote: > >> > >> There are ADC ICs which may have some of the AIN pins usable for other > >> functions. These ICs may have some of the AIN pins wired so that they > >> should not be used for ADC. > >> > >> (Preferred?) way for marking pins which can be used as ADC inputs is to > >> add corresponding channels@N nodes in the device tree as described in > >> the ADC binding yaml. > >> > >> Add couple of helper functions which can be used to retrieve the channel > >> information from the device node. > >> > >> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com> > >> > >> --- > > >> + * > >> + * Return: Number of found channels on succes. Negative value to indicate > > > > s/succes/success/ > > Thanks! > > >> +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, > >> + const struct iio_chan_spec *template, > >> + int max_chan_id, > >> + struct iio_chan_spec **cs) > >> +{ > >> + struct iio_chan_spec *chan_array, *chan; > >> + int num_chan = 0, ret; > >> + > >> + num_chan = iio_adc_device_num_channels(dev); > >> + if (num_chan < 1) > >> + return num_chan; > >> + > >> + chan_array = devm_kcalloc(dev, num_chan, sizeof(*chan_array), > >> + GFP_KERNEL); > >> + if (!chan_array) > >> + return -ENOMEM; > >> + > >> + chan = &chan_array[0]; > >> + > >> + device_for_each_child_node_scoped(dev, child) { > >> + u32 ch; > >> + > >> + if (!fwnode_name_eq(child, "channel")) > >> + continue; > >> + > >> + ret = fwnode_property_read_u32(child, "reg", &ch); > >> + if (ret) > >> + return ret; > >> + > >> + if (max_chan_id != -1 && ch > max_chan_id) > >> + return -ERANGE; > >> + > > > > Should we use return dev_err_probe() on these to help with debugging a bad dtb? > > > > I am not fan of using dev_err_probe() in a 'library code'. This is > because we never know if there'll be some odd use-case where this is not > called from the probe. > > All in all, I'd leave adding most of the debugs to the callers - > especially because we do not expect to have bad device-trees after the > initial 'development stage' of a board. The board 'development stage' > should really reveal bugs which prevent the channels from being > registered - and after the DT is correct, these debug prints become > unnecessary (albeit minor) binary bloat. > > >> + *chan = *template; > >> + chan->channel = ch; > >> + chan++; > >> + } > >> + > >> + *cs = chan_array; > >> + > >> + return num_chan; > >> +} > >> +EXPORT_SYMBOL_NS_GPL(devm_iio_adc_device_alloc_chaninfo_se, "IIO_DRIVER"); > > > > We can make this less verbose by setting #define > > DEFAULT_SYMBOL_NAMESPACE at the start of the file. Then we can just do > > EXPORT_SYMBOL_GPL() throughout the rest of the file. > > I am not sure what to think of this. I use the good old 'ctrl + ]' in my > editor when I need to check how a function was supposed to be used. That > jumps to the spot of code where the function is. I'd like to see the > namespace mentioned there in order to not accidentally miss the fact the > function belongs to one. > > OTOH, I do like simplifications. Yet, the added simplification might not > warrant the namespace not being visible in the function definition. > > > Also, I would prefer if the namespace matched config name (IIO_ADC_HELPER). > > I had some lengthy discussion about this with Andy and Jonathan during > earlier review versions. In short, I don't like the idea of very > fragmented namespaces in IIO, which will just complicate the drivers > without providing any obvious benefit. > > https://lore.kernel.org/all/20250222174842.57c091c5@jic23-huawei/ > > >> + > >> +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, > >> + const struct iio_chan_spec *template, > >> + int max_chan_id, > >> + struct iio_chan_spec **cs); > >> + > > > > There are some different opinions on this, but on the last patch I did > > introducing a new namespace, the consensus seems to be that putting > > the MODULE_IMPORT_NS() in the header file was convenient so that users > > of the API don't have to remember to both include the header and add > > the import macro. > > > > I do like this suggestion, and I believe this would be the balance > between getting the benefit of hiding part of the symbols - while not > unnecessarily complicating the callers. I know some people are opposing > it though. My personal opinion is that having the MODULE_IMPORT_NS() in > a header would be neatly simplifying the calling code with very little > harm, especially here where including the header hardly has use-cases > outside the IIO ADC. > > Unfortunately, the "safety" seems to often be a synonym for just "making > it intentionally hard". As Finnish people say: "Kärsi, kärsi, > kirkkaamman kruunun saat". :) > (Roughly translated as "Suffer, suffer, you will get a brighter crown"). > > Let's hear what Jonathan thinks of your suggestion. For this particular case my intent was that all the IIO exports that are suitable for use in simple IIO drives will be in this namespace, we just haven't started that conversion yet. As such, having it defined from a header for this helper isn't a good thing to do. Generally I prefer to see in driver code what namespaces are involved but do understand the other viewpoint. In this case I definitely don't think it is appropriate unless we go for a specific namespace for just this helper. Jonathan > > Thanks! > -- Matti >
On 08/03/2025 18:29, Jonathan Cameron wrote: > On Wed, 5 Mar 2025 12:54:33 +0200 > Matti Vaittinen <mazziesaccount@gmail.com> wrote: > >> Thanks for the review David. >> >> On 04/03/2025 11:25, David Lechner wrote: >>> On Mon, Mar 3, 2025 at 12:32 PM Matti Vaittinen >>> <mazziesaccount@gmail.com> wrote: >>>> >>>> There are ADC ICs which may have some of the AIN pins usable for other >>>> functions. These ICs may have some of the AIN pins wired so that they >>>> should not be used for ADC. >>>> >>>> (Preferred?) way for marking pins which can be used as ADC inputs is to >>>> add corresponding channels@N nodes in the device tree as described in >>>> the ADC binding yaml. >>>> >>>> Add couple of helper functions which can be used to retrieve the channel >>>> information from the device node. >>>> >>>> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com> >>>> >>>> --- >> >>>> + * >>>> + * Return: Number of found channels on succes. Negative value to indicate >>> >>> s/succes/success/ >> >> Thanks! >> >>>> +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, >>>> + const struct iio_chan_spec *template, >>>> + int max_chan_id, >>>> + struct iio_chan_spec **cs) >>>> +{ >>>> + struct iio_chan_spec *chan_array, *chan; >>>> + int num_chan = 0, ret; >>>> + >>>> + num_chan = iio_adc_device_num_channels(dev); >>>> + if (num_chan < 1) >>>> + return num_chan; >>>> + >>>> + chan_array = devm_kcalloc(dev, num_chan, sizeof(*chan_array), >>>> + GFP_KERNEL); >>>> + if (!chan_array) >>>> + return -ENOMEM; >>>> + >>>> + chan = &chan_array[0]; >>>> + >>>> + device_for_each_child_node_scoped(dev, child) { >>>> + u32 ch; >>>> + >>>> + if (!fwnode_name_eq(child, "channel")) >>>> + continue; >>>> + >>>> + ret = fwnode_property_read_u32(child, "reg", &ch); >>>> + if (ret) >>>> + return ret; >>>> + >>>> + if (max_chan_id != -1 && ch > max_chan_id) >>>> + return -ERANGE; >>>> + >>> >>> Should we use return dev_err_probe() on these to help with debugging a bad dtb? >>> >> >> I am not fan of using dev_err_probe() in a 'library code'. This is >> because we never know if there'll be some odd use-case where this is not >> called from the probe. >> >> All in all, I'd leave adding most of the debugs to the callers - >> especially because we do not expect to have bad device-trees after the >> initial 'development stage' of a board. The board 'development stage' >> should really reveal bugs which prevent the channels from being >> registered - and after the DT is correct, these debug prints become >> unnecessary (albeit minor) binary bloat. >> >>>> + *chan = *template; >>>> + chan->channel = ch; >>>> + chan++; >>>> + } >>>> + >>>> + *cs = chan_array; >>>> + >>>> + return num_chan; >>>> +} >>>> +EXPORT_SYMBOL_NS_GPL(devm_iio_adc_device_alloc_chaninfo_se, "IIO_DRIVER"); >>> >>> We can make this less verbose by setting #define >>> DEFAULT_SYMBOL_NAMESPACE at the start of the file. Then we can just do >>> EXPORT_SYMBOL_GPL() throughout the rest of the file. >> >> I am not sure what to think of this. I use the good old 'ctrl + ]' in my >> editor when I need to check how a function was supposed to be used. That >> jumps to the spot of code where the function is. I'd like to see the >> namespace mentioned there in order to not accidentally miss the fact the >> function belongs to one. >> >> OTOH, I do like simplifications. Yet, the added simplification might not >> warrant the namespace not being visible in the function definition. >> >>> Also, I would prefer if the namespace matched config name (IIO_ADC_HELPER). >> >> I had some lengthy discussion about this with Andy and Jonathan during >> earlier review versions. In short, I don't like the idea of very >> fragmented namespaces in IIO, which will just complicate the drivers >> without providing any obvious benefit. >> >> https://lore.kernel.org/all/20250222174842.57c091c5@jic23-huawei/ >> >>>> + >>>> +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, >>>> + const struct iio_chan_spec *template, >>>> + int max_chan_id, >>>> + struct iio_chan_spec **cs); >>>> + >>> >>> There are some different opinions on this, but on the last patch I did >>> introducing a new namespace, the consensus seems to be that putting >>> the MODULE_IMPORT_NS() in the header file was convenient so that users >>> of the API don't have to remember to both include the header and add >>> the import macro. >>> >> >> I do like this suggestion, and I believe this would be the balance >> between getting the benefit of hiding part of the symbols - while not >> unnecessarily complicating the callers. I know some people are opposing >> it though. My personal opinion is that having the MODULE_IMPORT_NS() in >> a header would be neatly simplifying the calling code with very little >> harm, especially here where including the header hardly has use-cases >> outside the IIO ADC. >> >> Unfortunately, the "safety" seems to often be a synonym for just "making >> it intentionally hard". As Finnish people say: "Kärsi, kärsi, >> kirkkaamman kruunun saat". :) >> (Roughly translated as "Suffer, suffer, you will get a brighter crown"). >> >> Let's hear what Jonathan thinks of your suggestion. > > For this particular case my intent was that all the IIO exports that > are suitable for use in simple IIO drives will be in this namespace, > we just haven't started that conversion yet. > > As such, having it defined from a header for this helper isn't a good > thing to do. Hmm. I agree. > Generally I prefer to see in driver code what namespaces > are involved but do understand the other viewpoint. In this case I > definitely don't think it is appropriate unless we go for a specific namespace > for just this helper. I suppose having the MODULE_IMPORT_NS() in the header would actually make the more fine-grained namespaces (like IIO_ADC_HELPERS, IIO_GTS, ...) much more usable. That'd relieved the drivers from explicitly listing multiple namespaces while nicely limiting the visibility. If IIO was my territory, I might want to ask people to go with that approach - but I am quite happy being a freeloade.. errm, I mean, bystander ;) Thanks! Yours, -- Matti
On Mon, 10 Mar 2025 09:41:00 +0200 Matti Vaittinen <mazziesaccount@gmail.com> wrote: > On 08/03/2025 18:29, Jonathan Cameron wrote: > > On Wed, 5 Mar 2025 12:54:33 +0200 > > Matti Vaittinen <mazziesaccount@gmail.com> wrote: > > > >> Thanks for the review David. > >> > >> On 04/03/2025 11:25, David Lechner wrote: > >>> On Mon, Mar 3, 2025 at 12:32 PM Matti Vaittinen > >>> <mazziesaccount@gmail.com> wrote: > >>>> > >>>> There are ADC ICs which may have some of the AIN pins usable for other > >>>> functions. These ICs may have some of the AIN pins wired so that they > >>>> should not be used for ADC. > >>>> > >>>> (Preferred?) way for marking pins which can be used as ADC inputs is to > >>>> add corresponding channels@N nodes in the device tree as described in > >>>> the ADC binding yaml. > >>>> > >>>> Add couple of helper functions which can be used to retrieve the channel > >>>> information from the device node. > >>>> > >>>> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com> > >>>> > >>>> --- > >> > >>>> + * > >>>> + * Return: Number of found channels on succes. Negative value to indicate > >>> > >>> s/succes/success/ > >> > >> Thanks! > >> > >>>> +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, > >>>> + const struct iio_chan_spec *template, > >>>> + int max_chan_id, > >>>> + struct iio_chan_spec **cs) > >>>> +{ > >>>> + struct iio_chan_spec *chan_array, *chan; > >>>> + int num_chan = 0, ret; > >>>> + > >>>> + num_chan = iio_adc_device_num_channels(dev); > >>>> + if (num_chan < 1) > >>>> + return num_chan; > >>>> + > >>>> + chan_array = devm_kcalloc(dev, num_chan, sizeof(*chan_array), > >>>> + GFP_KERNEL); > >>>> + if (!chan_array) > >>>> + return -ENOMEM; > >>>> + > >>>> + chan = &chan_array[0]; > >>>> + > >>>> + device_for_each_child_node_scoped(dev, child) { > >>>> + u32 ch; > >>>> + > >>>> + if (!fwnode_name_eq(child, "channel")) > >>>> + continue; > >>>> + > >>>> + ret = fwnode_property_read_u32(child, "reg", &ch); > >>>> + if (ret) > >>>> + return ret; > >>>> + > >>>> + if (max_chan_id != -1 && ch > max_chan_id) > >>>> + return -ERANGE; > >>>> + > >>> > >>> Should we use return dev_err_probe() on these to help with debugging a bad dtb? > >>> > >> > >> I am not fan of using dev_err_probe() in a 'library code'. This is > >> because we never know if there'll be some odd use-case where this is not > >> called from the probe. > >> > >> All in all, I'd leave adding most of the debugs to the callers - > >> especially because we do not expect to have bad device-trees after the > >> initial 'development stage' of a board. The board 'development stage' > >> should really reveal bugs which prevent the channels from being > >> registered - and after the DT is correct, these debug prints become > >> unnecessary (albeit minor) binary bloat. > >> > >>>> + *chan = *template; > >>>> + chan->channel = ch; > >>>> + chan++; > >>>> + } > >>>> + > >>>> + *cs = chan_array; > >>>> + > >>>> + return num_chan; > >>>> +} > >>>> +EXPORT_SYMBOL_NS_GPL(devm_iio_adc_device_alloc_chaninfo_se, "IIO_DRIVER"); > >>> > >>> We can make this less verbose by setting #define > >>> DEFAULT_SYMBOL_NAMESPACE at the start of the file. Then we can just do > >>> EXPORT_SYMBOL_GPL() throughout the rest of the file. > >> > >> I am not sure what to think of this. I use the good old 'ctrl + ]' in my > >> editor when I need to check how a function was supposed to be used. That > >> jumps to the spot of code where the function is. I'd like to see the > >> namespace mentioned there in order to not accidentally miss the fact the > >> function belongs to one. > >> > >> OTOH, I do like simplifications. Yet, the added simplification might not > >> warrant the namespace not being visible in the function definition. > >> > >>> Also, I would prefer if the namespace matched config name (IIO_ADC_HELPER). > >> > >> I had some lengthy discussion about this with Andy and Jonathan during > >> earlier review versions. In short, I don't like the idea of very > >> fragmented namespaces in IIO, which will just complicate the drivers > >> without providing any obvious benefit. > >> > >> https://lore.kernel.org/all/20250222174842.57c091c5@jic23-huawei/ > >> > >>>> + > >>>> +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, > >>>> + const struct iio_chan_spec *template, > >>>> + int max_chan_id, > >>>> + struct iio_chan_spec **cs); > >>>> + > >>> > >>> There are some different opinions on this, but on the last patch I did > >>> introducing a new namespace, the consensus seems to be that putting > >>> the MODULE_IMPORT_NS() in the header file was convenient so that users > >>> of the API don't have to remember to both include the header and add > >>> the import macro. > >>> > >> > >> I do like this suggestion, and I believe this would be the balance > >> between getting the benefit of hiding part of the symbols - while not > >> unnecessarily complicating the callers. I know some people are opposing > >> it though. My personal opinion is that having the MODULE_IMPORT_NS() in > >> a header would be neatly simplifying the calling code with very little > >> harm, especially here where including the header hardly has use-cases > >> outside the IIO ADC. > >> > >> Unfortunately, the "safety" seems to often be a synonym for just "making > >> it intentionally hard". As Finnish people say: "Kärsi, kärsi, > >> kirkkaamman kruunun saat". :) > >> (Roughly translated as "Suffer, suffer, you will get a brighter crown"). > >> > >> Let's hear what Jonathan thinks of your suggestion. > > > > For this particular case my intent was that all the IIO exports that > > are suitable for use in simple IIO drives will be in this namespace, > > we just haven't started that conversion yet. > > > > As such, having it defined from a header for this helper isn't a good > > thing to do. > > Hmm. I agree. > > > Generally I prefer to see in driver code what namespaces > > are involved but do understand the other viewpoint. In this case I > > definitely don't think it is appropriate unless we go for a specific namespace > > for just this helper. > > I suppose having the MODULE_IMPORT_NS() in the header would actually > make the more fine-grained namespaces (like IIO_ADC_HELPERS, IIO_GTS, > ...) much more usable. That'd relieved the drivers from explicitly > listing multiple namespaces while nicely limiting the visibility. > > If IIO was my territory, I might want to ask people to go with that > approach - but I am quite happy being a freeloade.. errm, I mean, > bystander ;) > It relieves the burden but I'd still prefer explicit opt in to namespaces unless there is general agreement on the approach of doing it in headers which there has not been so far. Jonathan > Thanks! > > Yours, > -- Matti
diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig index 849c90203071..37b70a65da6f 100644 --- a/drivers/iio/adc/Kconfig +++ b/drivers/iio/adc/Kconfig @@ -6,6 +6,9 @@ menu "Analog to digital converters" +config IIO_ADC_HELPER + tristate + config AB8500_GPADC bool "ST-Ericsson AB8500 GPADC driver" depends on AB8500_CORE && REGULATOR_AB8500 diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile index ee19afba62b7..1c410f483029 100644 --- a/drivers/iio/adc/Makefile +++ b/drivers/iio/adc/Makefile @@ -3,6 +3,8 @@ # Makefile for IIO ADC drivers # +obj-$(CONFIG_IIO_ADC_HELPER) += industrialio-adc.o + # When adding new entries keep the list in alphabetical order obj-$(CONFIG_AB8500_GPADC) += ab8500-gpadc.o obj-$(CONFIG_AD_SIGMA_DELTA) += ad_sigma_delta.o diff --git a/drivers/iio/adc/industrialio-adc.c b/drivers/iio/adc/industrialio-adc.c new file mode 100644 index 000000000000..7bdae5330224 --- /dev/null +++ b/drivers/iio/adc/industrialio-adc.c @@ -0,0 +1,82 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Helpers for parsing common ADC information from a firmware node. + * + * Copyright (c) 2025 Matti Vaittinen <mazziesaccount@gmail.com> + */ + +#include <linux/device.h> +#include <linux/errno.h> +#include <linux/export.h> +#include <linux/module.h> +#include <linux/property.h> +#include <linux/types.h> + +#include <linux/iio/adc-helpers.h> +#include <linux/iio/iio.h> + +/** + * devm_iio_adc_device_alloc_chaninfo_se - allocate and fill iio_chan_spec for ADC + * + * Scan the device node for single-ended ADC channel information. Channel ID is + * expected to be found from the "reg" property. Allocate and populate the + * iio_chan_spec structure corresponding to channels that are found. The memory + * for iio_chan_spec structure will be freed upon device detach. + * + * @dev: Pointer to the ADC device. + * @template: Template iio_chan_spec from which the fields of all + * found and allocated channels are initialized. + * @max_chan_id: Maximum value of a channel ID. Use -1 if no checking + * is required. + * @cs: Location where pointer to allocated iio_chan_spec + * should be stored. + * + * Return: Number of found channels on succes. Negative value to indicate + * failure. + */ +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, + const struct iio_chan_spec *template, + int max_chan_id, + struct iio_chan_spec **cs) +{ + struct iio_chan_spec *chan_array, *chan; + int num_chan = 0, ret; + + num_chan = iio_adc_device_num_channels(dev); + if (num_chan < 1) + return num_chan; + + chan_array = devm_kcalloc(dev, num_chan, sizeof(*chan_array), + GFP_KERNEL); + if (!chan_array) + return -ENOMEM; + + chan = &chan_array[0]; + + device_for_each_child_node_scoped(dev, child) { + u32 ch; + + if (!fwnode_name_eq(child, "channel")) + continue; + + ret = fwnode_property_read_u32(child, "reg", &ch); + if (ret) + return ret; + + if (max_chan_id != -1 && ch > max_chan_id) + return -ERANGE; + + *chan = *template; + chan->channel = ch; + chan++; + } + + *cs = chan_array; + + return num_chan; +} +EXPORT_SYMBOL_NS_GPL(devm_iio_adc_device_alloc_chaninfo_se, "IIO_DRIVER"); + +MODULE_LICENSE("GPL"); +MODULE_AUTHOR("Matti Vaittinen <mazziesaccount@gmail.com>"); +MODULE_DESCRIPTION("IIO ADC fwnode parsing helpers"); diff --git a/include/linux/iio/adc-helpers.h b/include/linux/iio/adc-helpers.h new file mode 100644 index 000000000000..403a70b109ec --- /dev/null +++ b/include/linux/iio/adc-helpers.h @@ -0,0 +1,27 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ + +/* + * The industrial I/O ADC firmware property parsing helpers + * + * Copyright (c) 2025 Matti Vaittinen <mazziesaccount@gmail.com> + */ + +#ifndef _INDUSTRIAL_IO_ADC_HELPERS_H_ +#define _INDUSTRIAL_IO_ADC_HELPERS_H_ + +#include <linux/property.h> + +struct device; +struct iio_chan_spec; + +static inline int iio_adc_device_num_channels(struct device *dev) +{ + return device_get_child_node_count_named(dev, "channel"); +} + +int devm_iio_adc_device_alloc_chaninfo_se(struct device *dev, + const struct iio_chan_spec *template, + int max_chan_id, + struct iio_chan_spec **cs); + +#endif /* _INDUSTRIAL_IO_ADC_HELPERS_H_ */
There are ADC ICs which may have some of the AIN pins usable for other functions. These ICs may have some of the AIN pins wired so that they should not be used for ADC. (Preferred?) way for marking pins which can be used as ADC inputs is to add corresponding channels@N nodes in the device tree as described in the ADC binding yaml. Add couple of helper functions which can be used to retrieve the channel information from the device node. Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com> --- Revision history: v4 => v5: - Inline iio_adc_device_num_channels() - Fix Indenting function parameters - Combine the max channel ID checks. v3 => v4: - Drop diff-channel support - Drop iio_adc_device_channels_by_property() - Add IIO_DEVICE namespace - Move industrialio-adc.o to top of the Makefile - Some styling as suggested by Andy - Re-consider included headers v2 => v3: Mostly based on review comments by Jonathan - Support differential and single-ended channels - Rename iio_adc_device_get_channels() as iio_adc_device_channels_by_property() - Improve spelling - Drop support for cases where DT comes from parent device's node - Decrease loop indent by reverting node name check conditions - Don't set 'chan->indexed' by number of channels to keep the interface consistent no matter how many channels are connected. - Fix ID range check and related comment RFC v1 => v2: - New patch --- drivers/iio/adc/Kconfig | 3 ++ drivers/iio/adc/Makefile | 2 + drivers/iio/adc/industrialio-adc.c | 82 ++++++++++++++++++++++++++++++ include/linux/iio/adc-helpers.h | 27 ++++++++++ 4 files changed, 114 insertions(+) create mode 100644 drivers/iio/adc/industrialio-adc.c create mode 100644 include/linux/iio/adc-helpers.h