Re: [PATCH] gpio: shared: call gpio_chip::of_xlate() if set

[Jon Hunter <jonathanh@nvidia.com>]

Hi Bartosz,

On 16/03/2026 13:52, Bartosz Golaszewski wrote:
> OF-based GPIO controller drivers may provide a translation function that
> calculates the real chip offset from whatever devicetree sources
> provide. We need to take this into account in the shared GPIO management
> and call of_xlate() if it's provided and adjust the entry->offset we
> initially set when scanning the tree.
> 
> To that end: modify the shared GPIO API to take the GPIO chip as
> argument on setup (to avoid having to rcu_dereference() it from the GPIO
> device) and protect the access to entry->offset with the existing lock.
> 
> Fixes: a060b8c511ab ("gpiolib: implement low-level, shared GPIO support")
> Reported-by: Jon Hunter <jonathanh@nvidia.com>
> Closes: https://lore.kernel.org/all/921ba8ce-b18e-4a99-966d-c763d22081e2@nvidia.com/
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
> ---
>   drivers/gpio/gpiolib-shared.c | 27 ++++++++++++++++++++++++++-
>   drivers/gpio/gpiolib-shared.h |  4 ++--
>   drivers/gpio/gpiolib.c        |  2 +-
>   3 files changed, 29 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib-shared.c b/drivers/gpio/gpiolib-shared.c
> index 17a7128b6bd9bf6023deccee50b2453caebe3d9a..3a8db9bf456daaf021d3c691677a90fc6da15889 100644
> --- a/drivers/gpio/gpiolib-shared.c
> +++ b/drivers/gpio/gpiolib-shared.c
> @@ -506,8 +506,9 @@ static void gpio_shared_remove_adev(struct auxiliary_device *adev)
>   	auxiliary_device_uninit(adev);
>   }
>   
> -int gpio_device_setup_shared(struct gpio_device *gdev)
> +int gpiochip_setup_shared(struct gpio_chip *gc)
>   {
> +	struct gpio_device *gdev = gc->gpiodev;
>   	struct gpio_shared_entry *entry;
>   	struct gpio_shared_ref *ref;
>   	struct gpio_desc *desc;
> @@ -532,12 +533,34 @@ int gpio_device_setup_shared(struct gpio_device *gdev)
>   	 * exposing shared pins. Find them and create the proxy devices.
>   	 */
>   	list_for_each_entry(entry, &gpio_shared_list, list) {
> +		guard(mutex)(&entry->lock);
> +
>   		if (!device_match_fwnode(&gdev->dev, entry->fwnode))
>   			continue;
>   
>   		if (list_count_nodes(&entry->refs) <= 1)
>   			continue;
>   
> +#if IS_ENABLED(CONFIG_OF)
> +		if (is_of_node(entry->fwnode) && gc->of_xlate) {
> +			/*
> +			 * This is the earliest that we can tranlate the
> +			 * devicetree offset to the chip offset.
> +			 */
> +			struct of_phandle_args gpiospec = { };
> +
> +			gpiospec.np = to_of_node(entry->fwnode);
> +			gpiospec.args_count = 2;
> +			gpiospec.args[0] = entry->offset;
> +
> +			ret = gc->of_xlate(gc, &gpiospec, NULL);
> +			if (ret < 0)
> +				return ret;
> +
> +			entry->offset = ret;
> +		}
> +#endif /* CONFIG_OF */
> +
>   		desc = &gdev->descs[entry->offset];
>   
>   		__set_bit(GPIOD_FLAG_SHARED, &desc->flags);
> @@ -575,6 +598,8 @@ void gpio_device_teardown_shared(struct gpio_device *gdev)
>   	struct gpio_shared_ref *ref;
>   
>   	list_for_each_entry(entry, &gpio_shared_list, list) {
> +		guard(mutex)(&entry->lock);
> +
>   		if (!device_match_fwnode(&gdev->dev, entry->fwnode))
>   			continue;
>   
> diff --git a/drivers/gpio/gpiolib-shared.h b/drivers/gpio/gpiolib-shared.h
> index 40568ef7364ccbf08b7f583e279a7d5b572af477..e11e260e1f590c46c5e575d3bb8f3b5a2240892d 100644
> --- a/drivers/gpio/gpiolib-shared.h
> +++ b/drivers/gpio/gpiolib-shared.h
> @@ -14,14 +14,14 @@ struct device;
>   
>   #if IS_ENABLED(CONFIG_GPIO_SHARED)
>   
> -int gpio_device_setup_shared(struct gpio_device *gdev);
> +int gpiochip_setup_shared(struct gpio_chip *gc);
>   void gpio_device_teardown_shared(struct gpio_device *gdev);
>   int gpio_shared_add_proxy_lookup(struct device *consumer, const char *con_id,
>   				 unsigned long lflags);
>   
>   #else
>   
> -static inline int gpio_device_setup_shared(struct gpio_device *gdev)
> +static inline int gpiochip_setup_shared(struct gpio_chip *gc)
>   {
>   	return 0;
>   }
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 6e000ad58a11f7e3de85d8a0630150368acc53ce..1777efe1a986c941da464da92255c261f27a5a6b 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1223,7 +1223,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
>   	if (ret)
>   		goto err_remove_irqchip_mask;
>   
> -	ret = gpio_device_setup_shared(gdev);
> +	ret = gpiochip_setup_shared(gc);
>   	if (ret)
>   		goto err_remove_irqchip;
>   
> 

Thanks for sending this. However, I am seeing a different issue now ...

  ------------[ cut here ]------------
  WARNING: drivers/gpio/gpiolib-shared.c:499 at gpio_shared_add_proxy_lookup+0x118/0x1d8, CPU#8: swapper/0/1
  Modules linked in:
  CPU: 8 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.0.0-rc3-next-20260309-00005-g02826fefa46f #14 PREEMPT
  Hardware name: NVIDIA NVIDIA Jetson AGX Orin Developer Kit/Jetson, BIOS buildbrain-gcid-42974706 11/20/2025
  pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
  pc : gpio_shared_add_proxy_lookup+0x118/0x1d8
  lr : gpio_shared_add_proxy_lookup+0xfc/0x1d8
  sp : ffff8000832bba30
  x29: ffff8000832bba30 x28: ffff000080d01010 x27: ffffffffffffefff
  x26: 0000000000000001 x25: ffff800082df0538 x24: ffff800082df0528
  x23: 0000000000000000 x22: ffff00008012c158 x21: ffff000081455010
  usb 1-3: new full-speed USB device number 2 using tegra-xusb
  x20: ffff000080d5d430 x19: ffff00008012c158 x18: 00000000ffffffff
  x17: ffff8000830786a8 x16: ffff800083078718 x15: ffff8000832bb880
  x14: ffffffffffffffff x13: 0000000000000008 x12: 0101010101010101
  x11: 7f7f7f7f7f7f7f7f x10: ffff8000827f20d0 x9 : 0000000000000003
  x8 : 0101010101010101 x7 : 0080808080808000 x6 : 15151a0a59460209
  x5 : 000000000000003c x4 : ffff8000832bb990 x3 : ffff0000800fe800
  x2 : ffff0000801c2f40 x1 : ffff0000801c2f40 x0 : ffff800082df0538
  Call trace:
   gpio_shared_add_proxy_lookup+0x118/0x1d8 (P)
   gpiod_find_and_request+0x1bc/0x548
   devm_fwnode_gpiod_get_index+0x1c/0x6c
   gpio_keys_probe+0x494/0x9fc
   platform_probe+0x5c/0x98
   really_probe+0xbc/0x2a8
   __driver_probe_device+0x78/0x12c
   driver_probe_device+0x3c/0x15c
   __driver_attach+0x90/0x19c
   bus_for_each_dev+0x78/0xd4
   driver_attach+0x24/0x30
   bus_add_driver+0xe4/0x208
   driver_register+0x5c/0x124
   __platform_driver_register+0x24/0x30
   gpio_keys_init+0x1c/0x28
   do_one_initcall+0x7c/0x1c0
   kernel_init_freeable+0x204/0x2ec
   kernel_init+0x24/0x1e0
   ret_from_fork+0x10/0x20
  ---[ end trace 0000000000000000 ]---

I see the comment says ...

  /* We warn here because this can only happen if the programmer borked. */
  WARN_ON(1);

I will take a closer look, but let me know if you have any thoughts?

Jon

-- 
nvpublic