linux-kernel - Re: [PATCH v3 2/2] rtc: max31335: add driver support

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Message-ID: <95e41f16-4b5f-4f2a-bc31-17273032312b@roeck-us.net>
Date:   Tue, 31 Oct 2023 09:01:16 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Antoniu Miclaus <antoniu.miclaus@...log.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>, linux-rtc@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v3 2/2] rtc: max31335: add driver support

On 10/31/23 08:30, Antoniu Miclaus wrote:
> RTC driver for MAX31335 ±2ppm Automotive Real-Time Clock with
> Integrated MEMS Resonator.
> 
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> ---
> changes in v3:
>   - drop MAX31335_STATUS1 register check inside probe function.
>   drivers/rtc/Kconfig        |  11 +
>   drivers/rtc/Makefile       |   1 +
>   drivers/rtc/rtc-max31335.c | 765 +++++++++++++++++++++++++++++++++++++
>   3 files changed, 777 insertions(+)
>   create mode 100644 drivers/rtc/rtc-max31335.c
> 
> diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
> index d7502433c78a..11c7d7fe1e85 100644
> --- a/drivers/rtc/Kconfig
> +++ b/drivers/rtc/Kconfig
> @@ -373,6 +373,17 @@ config RTC_DRV_MAX8997
>   	  This driver can also be built as a module. If so, the module
>   	  will be called rtc-max8997.
>   
> +config RTC_DRV_MAX31335
> +	tristate "Analog Devices MAX31335"
> +	depends on I2C
> +	select REGMAP_I2C
> +	help
> +	  If you say yes here you get support for the Analog Devices
> +	  MAX31335.
> +
> +	  This driver can also be built as a module. If so, the module
> +	  will be called rtc-max31335.
> +

Just out of curiosity, is this an unreleased chip ? I only find
MAX311331 and MAX31334 on the Analog website, but the register
map for those is different, and they don't support reporting
the chip temperature.

[ ... ]

> +
> +static const struct hwmon_channel_info *max31335_info[] = {
> +	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),

According to the register map above, the chip does support
low and high temperature limits as well as over- and undertemperature
alarms and interrupts. I would suggest to add support for all of those.
You might also consider adding support for temperature alarm interrupts
and report temperature alarm events by calling hwmon_notify_event()
if a thermal event occurs.

[ ... ]

> +
> +	hwmon = devm_hwmon_device_register_with_info(&client->dev, client->name,
> +						     max31335,
> +						     &max31335_chip_info,
> +						     NULL);

There is no "depends on HWMON" in the Kconfig entry, meaning this will fail
to compile if HWMON=n or if HWMON=m and RTC_DRV_MAX31335=y.

Guenter