Re: [PATCH v3] iio: adc: sun20i-gpadc: support non-contiguous channel lookups

[Jonathan Cameron <jic23@kernel.org>]

On Sat, 16 May 2026 07:48:37 +0200
Michal Piekos <michal.piekos@mmpsystems.pl> wrote:

> Using consumer driver like iio-hwmon which resolve channels through
> io-channels phandles will fail for sparse channels because IIO core by
> default treats phandle argument as index into channel array.
>         eg. <&gpadc 1> will fail if there is only channel@1 specified
> 
> Add .fwnode_xlate() which maps DT phandle to the registered channel
> whose chan->channel matches the hardware channel number. It allows
> sparse channel maps to be consumed by drivers like iio-hwmon.
> 
> Tested on Radxa Cubie A5E.
> 
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
> Signed-off-by: Michal Piekos <michal.piekos@mmpsystems.pl>
Applied to the testing branch of iio.git.

Thanks,

Jonathan

> ---
> Changes in v3:
> - Add iiospec->nargs validation in sun20i_gpadc_fwnode_xlate()
> - Keep Andy's Reviewed-by tag since change is narrow validation fix
> - Fix spelling issues in commit message
> - Link to v2: https://patch.msgid.link/20260514-fix-sunxi-gpadc-sparse-channels-v2-1-d4a66b70c7a7@mmpsystems.pl
> 
> Changes in v2:
> - Move loop variable declaration into the for statement
> - Fix indentation using clang-format
> - Correct commit wording
> - Link to v1: https://patch.msgid.link/20260513-fix-sunxi-gpadc-sparse-channels-v1-1-6c21e290bcee@mmpsystems.pl
> 
> To: Jonathan Cameron <jic23@kernel.org>
> To: David Lechner <dlechner@baylibre.com>
> To: Nuno Sá <nuno.sa@analog.com>
> To: Andy Shevchenko <andy@kernel.org>
> To: Chen-Yu Tsai <wens@kernel.org>
> To: Jernej Skrabec <jernej.skrabec@gmail.com>
> To: Samuel Holland <samuel@sholland.org>
> To: Nathan Chancellor <nathan@kernel.org>
> To: Nick Desaulniers <nick.desaulniers+lkml@gmail.com>
> To: Bill Wendling <morbo@google.com>
> To: Justin Stitt <justinstitt@google.com>
> Cc: linux-iio@vger.kernel.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-sunxi@lists.linux.dev
> Cc: linux-kernel@vger.kernel.org
> Cc: llvm@lists.linux.dev
> ---
>  drivers/iio/adc/sun20i-gpadc-iio.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/iio/adc/sun20i-gpadc-iio.c b/drivers/iio/adc/sun20i-gpadc-iio.c
> index 861c14da75ad..8a75498557ff 100644
> --- a/drivers/iio/adc/sun20i-gpadc-iio.c
> +++ b/drivers/iio/adc/sun20i-gpadc-iio.c
> @@ -139,8 +139,23 @@ static irqreturn_t sun20i_gpadc_irq_handler(int irq, void *data)
>  	return IRQ_HANDLED;
>  }
>  
> +static int
> +sun20i_gpadc_fwnode_xlate(struct iio_dev *indio_dev,
> +			  const struct fwnode_reference_args *iiospec)
> +{
> +	if (iiospec->nargs != 1)
> +		return -EINVAL;
> +
> +	for (unsigned int i = 0; i < indio_dev->num_channels; i++)
> +		if (indio_dev->channels[i].channel == iiospec->args[0])
> +			return i;
> +
> +	return -EINVAL;
> +}
> +
>  static const struct iio_info sun20i_gpadc_iio_info = {
>  	.read_raw = sun20i_gpadc_read_raw,
> +	.fwnode_xlate = sun20i_gpadc_fwnode_xlate,
>  };
>  
>  static void sun20i_gpadc_reset_assert(void *data)
> 
> ---
> base-commit: 6916d5703ddf9a38f1f6c2cc793381a24ee914c6
> change-id: 20260513-fix-sunxi-gpadc-sparse-channels-2b6b2063bd49
> 
> Best regards,
> --  
> Michal Piekos <michal.piekos@mmpsystems.pl>
> 
>