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@l...
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@l...
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@l...
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@l...
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@l...
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@l...
--- 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,
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++;
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++;
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
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.
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
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.
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.
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
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
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!
linux-stable-mirror@lists.linaro.org
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Andy Shevchenko -
Bartosz Golaszewski -
Linus Walleij