[PATCH v2] hwmon: (sun4i-lradc) Add driver for LRADC found on Allwinner A13/A20 SoC

[Maxime Ripard]

Hi,

On Thu, Apr 28, 2022 at 09:09:03PM +0000, Ruslan Zalata wrote:
> Some Allwinner SoCs like A13, A20 or T2 are equipped with two-channel
> low rate (6 bit) ADC that is often used for extra keys. There's a driver
> for that already implementing standard input device, but it has these
> limitations: 1) it cannot be used for general ADC data equisition, and
> 2) it uses only one LRADC channel of two available.
> 
> This driver provides basic hwmon interface to both channels of LRADC on
> such Allwinner SoCs.
> 
> Signed-off-by: Ruslan Zalata <rz at fabmicro.ru>
> ---
>  MAINTAINERS                       |   6 +
>  drivers/hwmon/Kconfig             |  13 ++
>  drivers/hwmon/Makefile            |   1 +
>  drivers/hwmon/sun4i-lradc-hwmon.c | 280 ++++++++++++++++++++++++++++++
>  4 files changed, 300 insertions(+)
>  create mode 100644 drivers/hwmon/sun4i-lradc-hwmon.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 5e8c2f61176..d9c71e94133 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -18861,6 +18861,12 @@ S:	Maintained
>  F:	Documentation/devicetree/bindings/input/allwinner,sun4i-a10-lradc-keys.yaml
>  F:	drivers/input/keyboard/sun4i-lradc-keys.c
>  
> +SUN4I LOW RES ADC HWMON DRIVER
> +M:	Ruslan Zalata <rz at fabmicro.ru>
> +L:	linux-hwmon at vger.kernel.org
> +S:	Maintained
> +F:	drivers/hwmon/sun4i-lradc-hwmon.c
> +
>  SUNDANCE NETWORK DRIVER
>  M:	Denis Kirjanov <kda at linux-powerpc.org>
>  L:	netdev at vger.kernel.org
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 68a8a27ab3b..86776488a81 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1691,6 +1691,19 @@ config SENSORS_SIS5595
>  	  This driver can also be built as a module. If so, the module
>  	  will be called sis5595.
>  
> +config SENSORS_SUN4I_LRADC
> +	tristate "Allwinner A13/A20 LRADC hwmon"
> +	depends on ARCH_SUNXI && !KEYBOARD_SUN4I_LRADC
> +	help
> +	  Say y here to support the LRADC found in Allwinner A13/A20 SoCs.
> +	  Both channels are supported.
> +
> +	  This driver can also be built as module. If so, the module
> +	  will be called sun4i-lradc-hwmon.
> +
> +	  This option is not compatible with KEYBOARD_SUN4I_LRADC, one
> +	  of these must be used at a time.

How do you plan on enforcing that?

I guess a better path forward would be to either register an hwmon
device in the original driver, or convert that driver to iio and use
iio-hwmon.

Maxime
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