linux-kernel - Re: [PATCH v4] leds: max597x: Add support for max597x

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Date:   Mon, 17 Apr 2023 15:10:31 +0530
From:   Naresh Solanki <naresh.solanki@...ements.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Lee Jones <lee@...nel.org>,
        Patrick Rudolph <patrick.rudolph@...ements.com>,
        linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org
Subject: Re: [PATCH v4] leds: max597x: Add support for max597x

Hi Pavel,

On 13-04-2023 04:43 pm, Pavel Machek wrote:
> Hi!
> 
>> From: Patrick Rudolph <patrick.rudolph@...ements.com>
>>
>> max597x is hot swap controller with indicator LED support.
>> This driver uses DT property to configure led during boot time &
>> also provide the LED control in sysfs.
>>
>> DTS example:
>>      i2c {
>>          #address-cells = <1>;
>>          #size-cells = <0>;
>>          regulator@3a {
>>              compatible = "maxim,max5978";
>>              reg = <0x3a>;
>>              vss1-supply = <&p3v3>;
>>
>>              regulators {
>>                  sw0_ref_0: sw0 {
>>                      shunt-resistor-micro-ohms = <12000>;
>>                  };
>>              };
>>
>>              leds {
>>                  #address-cells = <1>;
>>                  #size-cells = <0>;
>>                  led@0 {
>>                      reg = <0>;
>>                      label = "led0";
>>                      default-state = "on";
>>                  };
>>                  led@1 {
>>                      reg = <1>;
>>                      label = "led1";
>>                      default-state = "on";
>>                  };
>>              };
>>          };
>>      };
>>
> 
> Yeah, well, dts bindings need to be properly documented, and example
> goes to the binding, right?
Yes.
> 
> Plus, we should have better names than led0/led1. Something like
> hdd0:green:something, based on what the LED does and what are you hot
> swapping. See/modify Documentation/leds/well-known-leds.txt .
Yeah sure.
> 
> 
>> +static int max597x_led_set_brightness(struct led_classdev *cdev,
>> +				      enum led_brightness brightness)
>> +{
>> +	struct max597x_led *ddata = ldev_to_maxled(cdev);
>> +	int ret, val;
>> +
>> +	if (!ddata->regmap)
>> +		return -ENODEV;
>> +
>> +	/* Set/Clear corresponding bit for given led index */
> 
> "/clear".
Ack.
> 
>> +	val = !brightness ? BIT(ddata->index) : 0;
>> +	ret = regmap_update_bits(ddata->regmap, MAX5970_REG_LED_FLASH, BIT(ddata->index), val);
>> +	if (ret < 0)
>> +		dev_err(cdev->dev, "failed to set brightness %d", ret);
> 
> '\n"'.
Ack
> 
>> +	ddata->cdev.brightness_set_blocking = max597x_led_set_brightness;
>> +	ddata->cdev.default_trigger = "none";
> 
> So what do these leds normally do? Should they be registered with
> common function to handle default triggers etc?
Not sure if I understand your question right. In my use case in server 
motherboards, they are use to indicate presence of power for individual 
PCIe NVME connectors. Turning the LED on/off is handled by another 
application based on some conditions.
> 
>> +	ddata->index = reg;
>> +	ddata->regmap = regmap;
>> +	ret = devm_led_classdev_register(dev, &ddata->cdev);
>> +	if (ret)
>> +		dev_err(dev, "Error initializing LED %s", ddata->cdev.name);
> 
> '\n"'.
Ack
> 
>> +module_platform_driver(max597x_led_driver);
>> +MODULE_AUTHOR("Patrick Rudolph <patrick.rudolph@...ements.com>");
>> +MODULE_DESCRIPTION("MAX5970_hot-swap controller LED driver");
> 
> "MAX5970 hot-swap"?
max5970 is primarily a hotswap controller & it also had indication led 
support.
> 
>> +MODULE_LICENSE("GPL");
>>
>> base-commit: 11e572d06c23d61683e20a98bd16f550ef17ac65
>> prerequisite-patch-id: 456044abe991b2ff3b521d337825432789d71b29
> 
> ?? Send prerequisites in the series?
Will fix in v5.
> 
> BR,
> 								Pavel
Regards,
Naresh