On Wed, 02 Aug 2023, Marek Behún wrote:
> On Wed, 2 Aug 2023 18:07:47 +0200
> Marek Behún <kabel@xxxxxxxxxx> wrote:
>
> > +static int omnia_hwtrig_activate(struct led_classdev *cdev)
> > +{
> > + struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev);
> > + struct omnia_leds *leds = dev_get_drvdata(cdev->dev->parent);
> > + struct omnia_led *led = to_omnia_led(mc_cdev);
> > + int err = 0;
> > +
> > + mutex_lock(&leds->lock);
> > +
> > + if (!led->on) {
> > + /*
> > + * If the LED is off (brightness was set to 0), the last
> > + * configured color was not necessarily sent to the MCU.
> > + * Recompute with max_brightness and send if needed.
> > + */
> > + led_mc_calc_color_components(mc_cdev, cdev->max_brightness);
> > +
> > + if (omnia_led_channels_changed(led))
> > + err = omnia_led_send_color_cmd(leds->client, led);
> > + }
> > +
> > + if (!err) {
> > + /* put the LED into MCU controlled mode */
> > + err = omnia_cmd_write(leds->client, CMD_LED_MODE,
> > + CMD_LED_MODE_LED(led->reg));
> > + if (!err)
> > + led->hwtrig = true;
> > + }
> > +
> > + mutex_unlock(&leds->lock);
> > +
> > + return err;
> > +}
>
> Pavel, Lee, here I wanted to ask: can the .activate() method of a LED
> trigger sleep? The .brightness_set() method of a LED cannot sleep, and
> therefore we have .brightness_set_blocking() method, which schedules
> the potentially sleeping call into a work. But there is no such
> mechanism for the LED trigger .activate() method.
>
> I looked at the LED core code, and it does not seem to me that
> .activate() sleeping would cause issues, besides keeping trigger list
> lock locked...
>
> Note that previously none of the LED triggers in drivers/leds/trigger
> sleeped in .activate(), but recently the ethernet PHY subsystem was
> wired into the netdev trigger, which may cause the .activate() method
> to do a PHY transfer, which AFAIK may sleep...
I suspect you know more than I do at this point. I could take a
deep-dive into the code however a) I'm presently swamped with incoming
reviews and b) I do not have any additional resources at my disposable
than you do - it would consist of reading through and brain-grepping the
code.
Pavel or Jacek may have more knowledge at-hand though.
--
Lee Jones [李琼斯]
