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

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Date:   Mon, 2 May 2022 09:21:13 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     Ruslan Zalata <rz@...micro.ru>, Jean Delvare <jdelvare@...e.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-sunxi@...ts.linux.dev
Subject: Re: [PATCH v2] hwmon: (sun4i-lradc) Add driver for LRADC found on
 Allwinner A13/A20 SoC

On 5/2/22 06:39, Maxime Ripard wrote:
> On Mon, May 02, 2022 at 06:31:56AM -0700, Guenter Roeck wrote:
>> On 5/2/22 04:00, Maxime Ripard wrote:
>>> 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@...micro.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@...micro.ru>
>>>> +L:	linux-hwmon@...r.kernel.org
>>>> +S:	Maintained
>>>> +F:	drivers/hwmon/sun4i-lradc-hwmon.c
>>>> +
>>>>    SUNDANCE NETWORK DRIVER
>>>>    M:	Denis Kirjanov <kda@...ux-powerpc.org>
>>>>    L:	netdev@...r.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?
>>>
>> 	depends on ARCH_SUNXI && !KEYBOARD_SUN4I_LRADC
> 
> Right, but that just doesn't fly for any generic distro / build-system.
> 

That is correct. Alternative might be to use devicetree bindings, which
presumably will be needed anyway to tell the driver(s) what to bind to.

Guenter