Re: [PATCH] leds: pca955x: Allow full control over led name

[vishwanatha subbanna <vishwa@linux.vnet.ibm.com>]

Pavel / Dan,

Related to this below email, Can this https://github.com/openbmc/linux/blob/dev-5.10/drivers/leds/leds-pca955x.c#L507 naming change ever ?.

If there is any change in https://github.com/openbmc/linux/blob/dev-5.10/drivers/leds/leds-pca955x.c#L507, then my config having led names would break.
So, please suggest me what is the right approach here for defining LEDs. I have all LEDs defined as 


    leds {
        compatible = "gpio-leds”;

I am being asked by Joel Stanley that I should not do that way, but instead, have the LEDs defined as PCA_955X_LED and if I do that, I have this concern with the led names.

Thanks,
Vishwa.

> On 09-Apr-2021, at 4:43 PM, vishwanatha subbanna <vishwa@linux.vnet.ibm.com> wrote:
> 
> 
> Hello Pavel / Dan,
> 
> Wonder if you have any feedback on this patch from Joel ?.. This patch would help me have predictable LED names as I wanted instead of having the prefixes.
> I have some configuration files that depend on these names. So, if the LED name ( prefix ) changes in the future, then it breaks the configuration.
> 
> 
> I see good value in getting this patch in. Please could you help chime in ?
> 
> Thank you,
> !! Vishwa !!
> 
> 
>> On 25-Mar-2021, at 6:24 AM, Joel Stanley <joel@jms.id.au> wrote:
>> 
>> The PCA955x driver since it was merged has added a "pca955x:" prefix to
>> LED names. This meanas platform data (such as the device tree) cannot
>> fully control the name. Here's what this produces using the example in
>> the device tree bindings:
>> 
>> # cat /sys/class/leds/
>> pca955x:green:power/
>> pca955x:pca9552:white/
>> pca955x:pca9552:yellow/
>> pca955x:red:power/
>> 
>> Some systems want the ability to configure the full string. To do this,
>> introduce a build time option that adds the prefix that defaults to
>> enabled in order to preserve existing behaviour.
>> 
>> Signed-off-by: Joel Stanley <joel@jms.id.au>
>> ---
>> drivers/leds/Kconfig        | 11 +++++++++++
>> drivers/leds/leds-pca955x.c |  8 +++++++-
>> 2 files changed, 18 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
>> index b6742b4231bf..dcdb107e0967 100644
>> --- a/drivers/leds/Kconfig
>> +++ b/drivers/leds/Kconfig
>> @@ -519,6 +519,17 @@ config LEDS_PCA955X
>> 	  LED driver chips accessed via the I2C bus.  Supported
>> 	  devices include PCA9550, PCA9551, PCA9552, and PCA9553.
>> 
>> +config LEDS_PCA955X_SYSFS_PREFIX
>> +	bool "PCA955x sysfs prefix"
>> +	depends on LEDS_PCA955X
>> +	default y
>> +	help
>> +	  This option adds the string "pca955x:" to the start of the name
>> +	  presented in sysfs.
>> +
>> +	  If you wish to use the label provided by platform data without a
>> +	  prefix, disable this option.
>> +
>> config LEDS_PCA955X_GPIO
>> 	bool "Enable GPIO support for PCA955X"
>> 	depends on LEDS_PCA955X
>> diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
>> index 7087ca4592fc..b7742d6226b5 100644
>> --- a/drivers/leds/leds-pca955x.c
>> +++ b/drivers/leds/leds-pca955x.c
>> @@ -61,6 +61,12 @@
>> #define PCA955X_GPIO_HIGH	LED_OFF
>> #define PCA955X_GPIO_LOW	LED_FULL
>> 
>> +#ifdef CONFIG_LEDS_PCA955X_SYSFS_PREFIX
>> +#define SYSFS_NAME "pca955x:%s"
>> +#else
>> +#define SYSFS_NAME "%s"
>> +#endif
>> +
>> enum pca955x_type {
>> 	pca9550,
>> 	pca9551,
>> @@ -504,7 +510,7 @@ static int pca955x_probe(struct i2c_client *client,
>> 					sizeof(pdata->leds[i].name), "%d", i);
>> 
>> 			snprintf(pca955x_led->name,
>> -				sizeof(pca955x_led->name), "pca955x:%s",
>> +				sizeof(pca955x_led->name), SYSFS_NAME,
>> 				pdata->leds[i].name);
>> 
>> 			if (pdata->leds[i].default_trigger)
>> -- 
>> 2.30.2
>> 
>