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

Christian Marangi
2022-12-16T16:45:33Z

On Thu, Dec 15, 2022 at 04:13:03PM +0000, Russell King (Oracle) wrote:
> Hi Christian,
>
> Thanks for the patch.
>
> I think Andrew's email is offline at the moment.
>

Notice by gmail spamming me "I CAN'T SEND IT AHHHHH"
Holidy times I guess?

> 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;
> }
> ?

Much better!

>
> 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.
>

I added the default just to mute some compiler warning. But guess if
every enum is handled the warning should not be reported.

> > @@ -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?
>

trigger_set first remove any trigger and set the led off. Then apply the
new trigger. So the validation is done only when a trigger is actually
applied. Think we should understand the best case here.

> > @@ -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_ ?

Agree they are pretty generic so I can see why... My only concern was
making them too long... Maybe reduce them to SW or HW? LEDS_SW_ONLY...
LEDS_SW_CONTROLLED?

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

--
Ansuel