Subject: Re: [PATCH v7 01/11] leds: add support for hardware driven LEDs

From: "Russell King (Oracle)" <[email-masked]>
Date: Thu, 15 Dec 2022 16:13:03 +0000

Hi Christian,

Thanks for the patch.

I think Andrew's email is offline at the moment.

On Thu, Dec 15, 2022 at 12:54:28AM +0100, Christian Marangi wrote:
> +static bool led_trigger_is_supported(struct led_classdev *led_cdev,
> +				     struct led_trigger *trigger)
> +{
> +	switch (led_cdev->blink_mode) {
> +	case SOFTWARE_CONTROLLED:
> +		if (trigger->supported_blink_modes == HARDWARE_ONLY)
> +			return 0;
> +		break;
> +	case HARDWARE_CONTROLLED:
> +		if (trigger->supported_blink_modes == SOFTWARE_ONLY)
> +			return 0;
> +		break;
> +	case SOFTWARE_HARDWARE_CONTROLLED:
> +		break;
> +	default:
> +		return 0;
> +	}
> +
> +	return 1;

Should be returning true/false. I'm not sure I'm a fan of the style of
this though - wouldn't the following be easier to read?

	switch (led_cdev->blink_mode) {
	case SOFTWARE_CONTROLLED:
		return trigger->supported_blink_modes != HARDWARE_ONLY;

	case HARDWARE_CONTROLLED:
		return trigger->supported_blink_modes != SOFTWARE_ONLY;

	case SOFTWARE_HARDWARE_CONTROLLED:
		return true;
	}
?

Also, does it really need a default case - without it, when the
led_blink_modes enum is expanded and the switch statement isn't
updated, we'll get a compiler warning which will prompt this to be
updated - whereas, with a default case, it won't.

> @@ -188,6 +213,10 @@ int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
>  		led_set_brightness(led_cdev, LED_OFF);
>  	}
>  	if (trig) {
> +		/* Make sure the trigger support the LED blink mode */
> +		if (!led_trigger_is_supported(led_cdev, trig))
> +			return -EINVAL;

Shouldn't validation happen before we start taking any actions? In other
words, before we remove the previous trigger?

> @@ -350,12 +381,26 @@ static inline bool led_sysfs_is_disabled(struct led_classdev *led_cdev)
>  
>  #define TRIG_NAME_MAX 50
>  
> +enum led_trigger_blink_supported_modes {
> +	SOFTWARE_ONLY = SOFTWARE_CONTROLLED,
> +	HARDWARE_ONLY = HARDWARE_CONTROLLED,
> +	SOFTWARE_HARDWARE = SOFTWARE_HARDWARE_CONTROLLED,

I suspect all these generic names are asking for eventual namespace
clashes. Maybe prefix them with LED_ ?

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!