[PATCH v7 00/16] pinctrl: introduce the concept of a GPIO pin function category

[PATCH v7 00/16] pinctrl: introduce the concept of a GPIO pin function category

[Bartosz Golaszewski]

Problem: when pinctrl core binds pins to a consumer device and the
pinmux ops of the underlying driver are marked as strict, the pin in
question can no longer be requested as a GPIO using the GPIO descriptor
API. It will result in the following error:

[    5.095688] sc8280xp-tlmm f100000.pinctrl: pin GPIO_25 already requested by regulator-edp-3p3; cannot claim for f100000.pinctrl:570
[    5.107822] sc8280xp-tlmm f100000.pinctrl: error -EINVAL: pin-25 (f100000.pinctrl:570)

This typically makes sense except when the pins are muxed to a function
that actually says "GPIO". Of course, the function name is just a string
so it has no meaning to the pinctrl subsystem.

We have many Qualcomm SoCs (and I can imagine it's a common pattern in
other platforms as well) where we mux a pin to "gpio" function using the
`pinctrl-X` property in order to configure bias or drive-strength and
then access it using the gpiod API. This makes it impossible to mark the
pin controller module as "strict".

This series proposes to introduce a concept of a sub-category of
pinfunctions: GPIO functions where the above is not true and the pin
muxed as a GPIO can still be accessed via the GPIO consumer API even for
strict pinmuxers.

To that end: we first clean up the drivers that use struct function_desc
and make them use the smaller struct pinfunction instead - which is the
correct structure for drivers to describe their pin functions with. We
also rework pinmux core to not duplicate memory used to store the
pinfunctions unless they're allocated dynamically.

First: provide the kmemdup_const() helper which only duplicates memory
if it's not in the .rodata section. Then rework all pinctrl drivers that
instantiate objects of type struct function_desc as they should only be
created by pinmux core. Next constify the return value of the accessor
used to expose these structures to users and finally convert the
pinfunction object within struct function_desc to a pointer and use
kmemdup_const() to assign it. With this done proceed to add
infrastructure for the GPIO pin function category and use it in Qualcomm
drivers. At the very end: make the Qualcomm pinmuxer strict.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
Changes in v7:
- Add a patch checking the return value of the get_function_name()
  callback in pinmux_func_name_to_selector(). This fixes a NULL-pointer
  dereference on IMX platforms
- Don't assign the number of functions in pinctrl device in the IMX
  driver as it's done automatically when adding the pinfunctions using
  the provided API. This fixes a warning from pinctrl core on IMX
  platforms triggered by the conversion from accessing the radix tree
  directly
- Link to v6: https://lore.kernel.org/r/20250828-pinctrl-gpio-pinfuncs-v6-0-c9abb6bdb689@linaro.org

Changes in v6:
- Select GENERIC_PINMUX_FUNCTIONS when using generic pinmux helpers in
  qcom pinctrl drivers to fix build on ARM 32-bit platforms
- Assume that a pin can be requested in pin_request() if it has no
  mux_setting assigned
- Also check if a function is a GPIO for pins within GPIO ranges
- Fix an issue with the imx pinctrl driver where the conversion patch
  confused the function and pin group radix trees
- Add a FIXME to the imx driver mentioning the need to switch to the
  provided helpers for accessing the group radix tree
- Link to v5: https://lore.kernel.org/r/20250815-pinctrl-gpio-pinfuncs-v5-0-955de9fd91db@linaro.org

Changes in v5:
- Fix a potential NULL-pointer dereference in
  pinmux_can_be_used_for_gpio()
- Use PINCTRL_PINFUNCTION() in pinctrl-airoha
- Link to v4: https://lore.kernel.org/r/20250812-pinctrl-gpio-pinfuncs-v4-0-bb3906c55e64@linaro.org

Changes in v4:
- Update the GPIO pin function definitions to include the new qcom
  driver (milos)
- Provide devm_kmemdup_const() instead of a non-managed kmemdup_const()
  as a way to avoid casting out the 'const' modifier when passing the
  const pointer to devm_add_action_or_reset()
- Use devm_krealloc_array() where applicable instead of devm_krealloc()
- Fix typos
- Fix kerneldocs
- Improve commit messages
- Small tweaks as pointed out by Andy
- Rebased on top of v6.17-rc1
- Link to v3: https://lore.kernel.org/r/20250724-pinctrl-gpio-pinfuncs-v3-0-af4db9302de4@linaro.org

Changes in v3:
- Add more patches in front: convert pinctrl drivers to stop defining
  their own struct function_desc objects and make pinmux core not
  duplicate .rodata memory in which struct pinfunction objects are
  stored.
- Add a patch constifying pinmux_generic_get_function().
- Drop patches that were applied upstream.
- Link to v2: https://lore.kernel.org/r/20250709-pinctrl-gpio-pinfuncs-v2-0-b6135149c0d9@linaro.org

Changes in v2:
- Extend the series with providing pinmux_generic_add_pinfunction(),
  using it in several drivers and converting pinctrl-msm to using
  generic pinmux helpers
- Add a generic function_is_gpio() callback for pinmux_ops
- Convert all qualcomm drivers to using the new GPIO pin category so
  that we can actually enable the strict flag
- Link to v1: https://lore.kernel.org/r/20250702-pinctrl-gpio-pinfuncs-v1-0-ed2bd0f9468d@linaro.org

---
Bartosz Golaszewski (16):
      pinctrl: check the return value of pinmux_ops::get_function_name()
      devres: provide devm_kmemdup_const()
      pinctrl: ingenic: use struct pinfunction instead of struct function_desc
      pinctrl: airoha: replace struct function_desc with struct pinfunction
      pinctrl: mediatek: mt7988: use PINCTRL_PIN_FUNCTION()
      pinctrl: mediatek: moore: replace struct function_desc with struct pinfunction
      pinctrl: imx: don't access the pin function radix tree directly
      pinctrl: keembay: release allocated memory in detach path
      pinctrl: keembay: use a dedicated structure for the pinfunction description
      pinctrl: constify pinmux_generic_get_function()
      pinctrl: make struct pinfunction a pointer in struct function_desc
      pinctrl: qcom: use generic pin function helpers
      pinctrl: allow to mark pin functions as requestable GPIOs
      pinctrl: qcom: add infrastructure for marking pin functions as GPIOs
      pinctrl: qcom: mark the `gpio` and `egpio` pins function as non-strict functions
      pinctrl: qcom: make the pinmuxing strict

 drivers/base/devres.c                            | 21 +++++++
 drivers/pinctrl/freescale/pinctrl-imx.c          | 45 +++++++--------
 drivers/pinctrl/mediatek/pinctrl-airoha.c        | 19 +++----
 drivers/pinctrl/mediatek/pinctrl-moore.c         | 10 ++--
 drivers/pinctrl/mediatek/pinctrl-moore.h         |  7 +--
 drivers/pinctrl/mediatek/pinctrl-mt7622.c        |  2 +-
 drivers/pinctrl/mediatek/pinctrl-mt7623.c        |  2 +-
 drivers/pinctrl/mediatek/pinctrl-mt7629.c        |  2 +-
 drivers/pinctrl/mediatek/pinctrl-mt7981.c        |  2 +-
 drivers/pinctrl/mediatek/pinctrl-mt7986.c        |  2 +-
 drivers/pinctrl/mediatek/pinctrl-mt7988.c        | 44 ++++++---------
 drivers/pinctrl/mediatek/pinctrl-mtk-common-v2.h |  2 +-
 drivers/pinctrl/pinctrl-equilibrium.c            |  2 +-
 drivers/pinctrl/pinctrl-ingenic.c                | 49 ++++++++---------
 drivers/pinctrl/pinctrl-keembay.c                | 26 ++++++---
 drivers/pinctrl/pinctrl-single.c                 |  4 +-
 drivers/pinctrl/pinmux.c                         | 70 ++++++++++++++++++++----
 drivers/pinctrl/pinmux.h                         |  9 ++-
 drivers/pinctrl/qcom/Kconfig                     |  1 +
 drivers/pinctrl/qcom/pinctrl-ipq5018.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-ipq5332.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-ipq5424.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-ipq6018.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-ipq8074.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-ipq9574.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-mdm9607.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-mdm9615.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-milos.c             |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm.c               | 45 +++++----------
 drivers/pinctrl/qcom/pinctrl-msm.h               |  5 ++
 drivers/pinctrl/qcom/pinctrl-msm8226.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm8660.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm8909.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm8916.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm8917.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm8953.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm8960.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm8976.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm8994.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm8996.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm8998.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-msm8x74.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-qcm2290.c           |  4 +-
 drivers/pinctrl/qcom/pinctrl-qcs404.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-qcs615.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-qcs8300.c           |  4 +-
 drivers/pinctrl/qcom/pinctrl-qdu1000.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-sa8775p.c           |  4 +-
 drivers/pinctrl/qcom/pinctrl-sar2130p.c          |  2 +-
 drivers/pinctrl/qcom/pinctrl-sc7180.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sc7280.c            |  4 +-
 drivers/pinctrl/qcom/pinctrl-sc8180x.c           |  2 +-
 drivers/pinctrl/qcom/pinctrl-sc8280xp.c          |  4 +-
 drivers/pinctrl/qcom/pinctrl-sdm660.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sdm670.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sdm845.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sdx55.c             |  2 +-
 drivers/pinctrl/qcom/pinctrl-sdx65.c             |  2 +-
 drivers/pinctrl/qcom/pinctrl-sdx75.c             |  2 +-
 drivers/pinctrl/qcom/pinctrl-sm4450.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sm6115.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sm6125.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sm6350.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sm6375.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sm7150.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sm8150.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sm8250.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sm8350.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sm8450.c            |  4 +-
 drivers/pinctrl/qcom/pinctrl-sm8550.c            |  2 +-
 drivers/pinctrl/qcom/pinctrl-sm8650.c            |  4 +-
 drivers/pinctrl/qcom/pinctrl-sm8750.c            |  4 +-
 drivers/pinctrl/qcom/pinctrl-x1e80100.c          |  2 +-
 drivers/pinctrl/renesas/pinctrl-rza1.c           |  2 +-
 drivers/pinctrl/renesas/pinctrl-rza2.c           |  2 +-
 drivers/pinctrl/renesas/pinctrl-rzg2l.c          |  2 +-
 drivers/pinctrl/renesas/pinctrl-rzv2m.c          |  2 +-
 include/linux/device/devres.h                    |  2 +
 include/linux/pinctrl/pinctrl.h                  | 14 +++++
 include/linux/pinctrl/pinmux.h                   |  2 +
 80 files changed, 288 insertions(+), 227 deletions(-)
---
base-commit: b320789d6883cc00ac78ce83bccbfe7ed58afcf0
change-id: 20250701-pinctrl-gpio-pinfuncs-de82bd9aac43

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

[PATCH v7 01/16] pinctrl: check the return value of pinmux_ops::get_function_name()

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

While the API contract in docs doesn't specify it explicitly, the
generic implementation of the get_function_name() callback from struct
pinmux_ops - pinmux_generic_get_function_name() - can fail and return
NULL. This is already checked in pinmux_check_ops() so add a similar
check in pinmux_func_name_to_selector() instead of passing the returned
pointer right down to strcmp() where the NULL can get dereferenced. This
is normal operation when adding new pinfunctions.

Cc: stable@vger.kernel.org
Tested-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/pinctrl/pinmux.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index 79814758a084570adea0ea1a3151d186f65d1d1f..07a478b2c48740c24a32e6ac8f10df4876e718e3 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -337,7 +337,7 @@ static int pinmux_func_name_to_selector(struct pinctrl_dev *pctldev,
 	while (selector < nfuncs) {
 		const char *fname = ops->get_function_name(pctldev, selector);
 
-		if (!strcmp(function, fname))
+		if (fname && !strcmp(function, fname))
 			return selector;
 
 		selector++;

-- 
2.48.1

Re: [PATCH v7 01/16] pinctrl: check the return value of pinmux_ops::get_function_name()

[Andy Shevchenko]

On Tue, Sep 02, 2025 at 01:59:10PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> 
> While the API contract in docs doesn't specify it explicitly,

So, why not to amend the doc at the same time?

> the generic implementation of the get_function_name() callback from struct
> pinmux_ops - pinmux_generic_get_function_name() - can fail and return
> NULL. This is already checked in pinmux_check_ops() so add a similar
> check in pinmux_func_name_to_selector() instead of passing the returned
> pointer right down to strcmp() where the NULL can get dereferenced. This
> is normal operation when adding new pinfunctions.

Fixes?
Reported?
Closes?

...

>  	while (selector < nfuncs) {
>  		const char *fname = ops->get_function_name(pctldev, selector);
>  
> -		if (!strcmp(function, fname))
> +		if (fname && !strcmp(function, fname))
>  			return selector;

I would slightly refactor this:

		const char *fname;

		fname = ops->get_function_name(pctldev, selector);
		if (fname && !strcmp(function, fname))
			return selector;

>  		selector++;

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v7 01/16] pinctrl: check the return value of pinmux_ops::get_function_name()

[Bartosz Golaszewski]

On Tue, Sep 2, 2025 at 3:06 PM Andy Shevchenko
<andriy.shevchenko@intel.com> wrote:
>
> On Tue, Sep 02, 2025 at 01:59:10PM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > While the API contract in docs doesn't specify it explicitly,
>
> So, why not to amend the doc at the same time?
>

Because this series is already big as is. That would be another commit
that can be separate.

> > the generic implementation of the get_function_name() callback from struct
> > pinmux_ops - pinmux_generic_get_function_name() - can fail and return
> > NULL. This is already checked in pinmux_check_ops() so add a similar
> > check in pinmux_func_name_to_selector() instead of passing the returned
> > pointer right down to strcmp() where the NULL can get dereferenced. This
> > is normal operation when adding new pinfunctions.
>
> Fixes?

This has always been like that.

> Reported?

I mean, technically Mark Brown reported my previous patch failing but
I don't think we do this if we're still within the same series just
another iteration?

> Closes?

Ditto.

>
> ...
>
> >       while (selector < nfuncs) {
> >               const char *fname = ops->get_function_name(pctldev, selector);
> >
> > -             if (!strcmp(function, fname))
> > +             if (fname && !strcmp(function, fname))
> >                       return selector;
>
> I would slightly refactor this:
>
>                 const char *fname;
>
>                 fname = ops->get_function_name(pctldev, selector);
>                 if (fname && !strcmp(function, fname))
>                         return selector;
>
> >               selector++;
>

You can do this in a subsequent patch, I prefer a smaller diff personally.

Bartosz

Re: [PATCH v7 01/16] pinctrl: check the return value of pinmux_ops::get_function_name()

[Andy Shevchenko]

On Tue, Sep 02, 2025 at 03:29:31PM +0200, Bartosz Golaszewski wrote:
> On Tue, Sep 2, 2025 at 3:06 PM Andy Shevchenko
> <andriy.shevchenko@intel.com> wrote:
> > On Tue, Sep 02, 2025 at 01:59:10PM +0200, Bartosz Golaszewski wrote:
> > >
> > > While the API contract in docs doesn't specify it explicitly,
> >
> > So, why not to amend the doc at the same time?
> 
> Because this series is already big as is. That would be another commit
> that can be separate.

I meant _in the same_ patch.

> > > the generic implementation of the get_function_name() callback from struct
> > > pinmux_ops - pinmux_generic_get_function_name() - can fail and return
> > > NULL. This is already checked in pinmux_check_ops() so add a similar
> > > check in pinmux_func_name_to_selector() instead of passing the returned
> > > pointer right down to strcmp() where the NULL can get dereferenced. This
> > > is normal operation when adding new pinfunctions.

> > Fixes?
> 
> This has always been like that.
> 
> > Reported?
> 
> I mean, technically Mark Brown reported my previous patch failing but
> I don't think we do this if we're still within the same series just
> another iteration?
> 
> > Closes?
> 
> Ditto.

I meant that this fixes a potential issue disregard to your series, right?

...

> > >       while (selector < nfuncs) {
> > >               const char *fname = ops->get_function_name(pctldev, selector);
> > >
> > > -             if (!strcmp(function, fname))
> > > +             if (fname && !strcmp(function, fname))
> > >                       return selector;
> >
> > I would slightly refactor this:
> >
> >                 const char *fname;
> >
> >                 fname = ops->get_function_name(pctldev, selector);
> >                 if (fname && !strcmp(function, fname))
> >                         return selector;
> >
> > >               selector++;
> >
> 
> You can do this in a subsequent patch, I prefer a smaller diff personally.

Sure.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v7 01/16] pinctrl: check the return value of pinmux_ops::get_function_name()

[Bartosz Golaszewski]

On Tue, Sep 2, 2025 at 3:50 PM Andy Shevchenko
<andriy.shevchenko@intel.com> wrote:
>
> On Tue, Sep 02, 2025 at 03:29:31PM +0200, Bartosz Golaszewski wrote:
> > On Tue, Sep 2, 2025 at 3:06 PM Andy Shevchenko
> > <andriy.shevchenko@intel.com> wrote:
> > > On Tue, Sep 02, 2025 at 01:59:10PM +0200, Bartosz Golaszewski wrote:
> > > >
> > > > While the API contract in docs doesn't specify it explicitly,
> > >
> > > So, why not to amend the doc at the same time?
> >
> > Because this series is already big as is. That would be another commit
> > that can be separate.
>
> I meant _in the same_ patch.
>
> > > > the generic implementation of the get_function_name() callback from struct
> > > > pinmux_ops - pinmux_generic_get_function_name() - can fail and return
> > > > NULL. This is already checked in pinmux_check_ops() so add a similar
> > > > check in pinmux_func_name_to_selector() instead of passing the returned
> > > > pointer right down to strcmp() where the NULL can get dereferenced. This
> > > > is normal operation when adding new pinfunctions.
>
> > > Fixes?
> >
> > This has always been like that.
> >
> > > Reported?
> >
> > I mean, technically Mark Brown reported my previous patch failing but
> > I don't think we do this if we're still within the same series just
> > another iteration?
> >
> > > Closes?
> >
> > Ditto.
>
> I meant that this fixes a potential issue disregard to your series, right?
>

No, as long as the imx driver keeps putting stuff into the pin
function radix tree directly, this cannot happen. The issue was
triggered by the discrepancy between the number of added selectors and
the hardcoded number of functions (we started at 0 which was not in
the radix tree and crashed before we got to 1).

Bart

Re: [PATCH v7 01/16] pinctrl: check the return value of pinmux_ops::get_function_name()

[Andy Shevchenko]

On Tue, Sep 02, 2025 at 04:02:27PM +0200, Bartosz Golaszewski wrote:
> On Tue, Sep 2, 2025 at 3:50 PM Andy Shevchenko
> <andriy.shevchenko@intel.com> wrote:
> > On Tue, Sep 02, 2025 at 03:29:31PM +0200, Bartosz Golaszewski wrote:
> > > On Tue, Sep 2, 2025 at 3:06 PM Andy Shevchenko
> > > <andriy.shevchenko@intel.com> wrote:
> > > > On Tue, Sep 02, 2025 at 01:59:10PM +0200, Bartosz Golaszewski wrote:

...

> > > > Fixes?
> > >
> > > This has always been like that.
> > >
> > > > Reported?
> > >
> > > I mean, technically Mark Brown reported my previous patch failing but
> > > I don't think we do this if we're still within the same series just
> > > another iteration?
> > >
> > > > Closes?
> > >
> > > Ditto.
> >
> > I meant that this fixes a potential issue disregard to your series, right?
> 
> No, as long as the imx driver keeps putting stuff into the pin
> function radix tree directly, this cannot happen. The issue was
> triggered by the discrepancy between the number of added selectors and
> the hardcoded number of functions (we started at 0 which was not in
> the radix tree and crashed before we got to 1).

Ah, thanks for the explanation. The problem is that current commit message
implies a (potential) but lurking somewhere (regardless IMX case). Can you
amend it to make more explicit that there is no bug right now.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v7 00/16] pinctrl: introduce the concept of a GPIO pin function category

[Andy Shevchenko]

On Tue, Sep 02, 2025 at 01:59:09PM +0200, Bartosz Golaszewski wrote:
> Problem: when pinctrl core binds pins to a consumer device and the
> pinmux ops of the underlying driver are marked as strict, the pin in
> question can no longer be requested as a GPIO using the GPIO descriptor
> API. It will result in the following error:
> 
> [    5.095688] sc8280xp-tlmm f100000.pinctrl: pin GPIO_25 already requested by regulator-edp-3p3; cannot claim for f100000.pinctrl:570
> [    5.107822] sc8280xp-tlmm f100000.pinctrl: error -EINVAL: pin-25 (f100000.pinctrl:570)
> 
> This typically makes sense except when the pins are muxed to a function
> that actually says "GPIO". Of course, the function name is just a string
> so it has no meaning to the pinctrl subsystem.
> 
> We have many Qualcomm SoCs (and I can imagine it's a common pattern in
> other platforms as well) where we mux a pin to "gpio" function using the
> `pinctrl-X` property in order to configure bias or drive-strength and
> then access it using the gpiod API. This makes it impossible to mark the
> pin controller module as "strict".
> 
> This series proposes to introduce a concept of a sub-category of
> pinfunctions: GPIO functions where the above is not true and the pin
> muxed as a GPIO can still be accessed via the GPIO consumer API even for
> strict pinmuxers.
> 
> To that end: we first clean up the drivers that use struct function_desc
> and make them use the smaller struct pinfunction instead - which is the
> correct structure for drivers to describe their pin functions with. We
> also rework pinmux core to not duplicate memory used to store the
> pinfunctions unless they're allocated dynamically.
> 
> First: provide the kmemdup_const() helper which only duplicates memory
> if it's not in the .rodata section. Then rework all pinctrl drivers that
> instantiate objects of type struct function_desc as they should only be
> created by pinmux core. Next constify the return value of the accessor
> used to expose these structures to users and finally convert the
> pinfunction object within struct function_desc to a pointer and use
> kmemdup_const() to assign it. With this done proceed to add
> infrastructure for the GPIO pin function category and use it in Qualcomm
> drivers. At the very end: make the Qualcomm pinmuxer strict.

I read all this and do not understand why we take all this way,
Esp. see my Q in patch 16. Can we rather limit this to the controller
driver to decide and have it handle all the possible configurations,
muxing, etc?

I think what we are trying to do here is to delegate part of the
driver's work pin mux / pin control core. While it sounds like right
direction the implementation (design wise) seems to me unscalable.

In any case first 12 patch (in case they are not regressing) are good
to go as soon as they can. I like the part of constification.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v7 00/16] pinctrl: introduce the concept of a GPIO pin function category

[Bartosz Golaszewski]

On Tue, Sep 2, 2025 at 4:46 PM Andy Shevchenko
<andriy.shevchenko@intel.com> wrote:
>
> On Tue, Sep 02, 2025 at 01:59:09PM +0200, Bartosz Golaszewski wrote:
> > Problem: when pinctrl core binds pins to a consumer device and the
> > pinmux ops of the underlying driver are marked as strict, the pin in
> > question can no longer be requested as a GPIO using the GPIO descriptor
> > API. It will result in the following error:
> >
> > [    5.095688] sc8280xp-tlmm f100000.pinctrl: pin GPIO_25 already requested by regulator-edp-3p3; cannot claim for f100000.pinctrl:570
> > [    5.107822] sc8280xp-tlmm f100000.pinctrl: error -EINVAL: pin-25 (f100000.pinctrl:570)
> >
> > This typically makes sense except when the pins are muxed to a function
> > that actually says "GPIO". Of course, the function name is just a string
> > so it has no meaning to the pinctrl subsystem.
> >
> > We have many Qualcomm SoCs (and I can imagine it's a common pattern in
> > other platforms as well) where we mux a pin to "gpio" function using the
> > `pinctrl-X` property in order to configure bias or drive-strength and
> > then access it using the gpiod API. This makes it impossible to mark the
> > pin controller module as "strict".
> >
> > This series proposes to introduce a concept of a sub-category of
> > pinfunctions: GPIO functions where the above is not true and the pin
> > muxed as a GPIO can still be accessed via the GPIO consumer API even for
> > strict pinmuxers.
> >
> > To that end: we first clean up the drivers that use struct function_desc
> > and make them use the smaller struct pinfunction instead - which is the
> > correct structure for drivers to describe their pin functions with. We
> > also rework pinmux core to not duplicate memory used to store the
> > pinfunctions unless they're allocated dynamically.
> >
> > First: provide the kmemdup_const() helper which only duplicates memory
> > if it's not in the .rodata section. Then rework all pinctrl drivers that
> > instantiate objects of type struct function_desc as they should only be
> > created by pinmux core. Next constify the return value of the accessor
> > used to expose these structures to users and finally convert the
> > pinfunction object within struct function_desc to a pointer and use
> > kmemdup_const() to assign it. With this done proceed to add
> > infrastructure for the GPIO pin function category and use it in Qualcomm
> > drivers. At the very end: make the Qualcomm pinmuxer strict.
>
> I read all this and do not understand why we take all this way,
> Esp. see my Q in patch 16. Can we rather limit this to the controller
> driver to decide and have it handle all the possible configurations,
> muxing, etc?
>
> I think what we are trying to do here is to delegate part of the
> driver's work pin mux / pin control core. While it sounds like right
> direction the implementation (design wise) seems to me unscalable.
>
> In any case first 12 patch (in case they are not regressing) are good
> to go as soon as they can. I like the part of constification.
>

I'm not sure how to rephrase it. Strict pinmuxers are already a thing,
but on many platforms it's impossible to use them BECAUSE pinctrl
doesn't care about what a function does semantically. It just so
happens that some functions are GPIOs and as such can also be used by
GPIOLIB. Except that if the pinmuxer is "strict", any gpiod_get() call
will fail BECAUSE pinctrl does not know that a function called "gpio"
is actually a GPIO and will say NO if anything tries to request a
muxed pin. This (the function name) is just a string, it could as well
be called "andy" for all pinctrl cares. This is why we're doing it at
the pinctrl core level - because it will benefit many other platforms
as Linus mentioned elsewhere - he has some other platforms lined up
for a similar conversion. And also because it cannot be done at the
driver level at the moment, it's the pinctrl core that says "NO" to
GPIOLIB. I think you missed the entire point of this series.

Bartosz

Re: [PATCH v7 00/16] pinctrl: introduce the concept of a GPIO pin function category

[Linus Walleij]

On Tue, Sep 2, 2025 at 1:59 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:

> We have many Qualcomm SoCs (and I can imagine it's a common pattern in
> other platforms as well) where we mux a pin to "gpio" function using the
> `pinctrl-X` property in order to configure bias or drive-strength and
> then access it using the gpiod API. This makes it impossible to mark the
> pin controller module as "strict".
>
> This series proposes to introduce a concept of a sub-category of
> pinfunctions: GPIO functions where the above is not true and the pin
> muxed as a GPIO can still be accessed via the GPIO consumer API even for
> strict pinmuxers.

This is what I want for pin control, and fixes an ages old issue
that pin control has no intrinsic awareness of if a pin is muxed
to a function providing GPIO.
So patches applied!

Any remaining code nitpicks can be fixed in-tree, I need this
to be able to apply the much desired Broadcom STB driver,
so this needs to go into -next now for cooking.

I also want to strictify some drivers using this, bringing GPIO
function awareness into them, which is a good thing!

Yours,
Linus Walleij

Re: [PATCH v7 00/16] pinctrl: introduce the concept of a GPIO pin function category

[Andy Shevchenko]

On Wed, Sep 03, 2025 at 12:18:18AM +0200, Linus Walleij wrote:
> On Tue, Sep 2, 2025 at 1:59 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:
> 
> > We have many Qualcomm SoCs (and I can imagine it's a common pattern in
> > other platforms as well) where we mux a pin to "gpio" function using the
> > `pinctrl-X` property in order to configure bias or drive-strength and
> > then access it using the gpiod API. This makes it impossible to mark the
> > pin controller module as "strict".
> >
> > This series proposes to introduce a concept of a sub-category of
> > pinfunctions: GPIO functions where the above is not true and the pin
> > muxed as a GPIO can still be accessed via the GPIO consumer API even for
> > strict pinmuxers.
> 
> This is what I want for pin control, and fixes an ages old issue
> that pin control has no intrinsic awareness of if a pin is muxed
> to a function providing GPIO.
> So patches applied!

No objections, let's move on.

> Any remaining code nitpicks can be fixed in-tree, I need this
> to be able to apply the much desired Broadcom STB driver,
> so this needs to go into -next now for cooking.
> 
> I also want to strictify some drivers using this, bringing GPIO
> function awareness into them, which is a good thing!

Well said!

-- 
With Best Regards,
Andy Shevchenko