Re: [PATCH v3 2/2] leds: add sgm3140 driver

[Jacek Anaszewski]

Hi Luca,

On 4/27/20 9:49 PM, Luca Weiss wrote:
> On Montag, 27. April 2020 11:51:02 CEST Pavel Machek wrote:
> > Hi!
> >
> > > Add a driver for the SGMICRO SGM3140 Buck/Boost Charge Pump LED driver.
> > >
> > > This device is controlled by two GPIO pins, one for enabling and the
> > > second one for switching between torch and flash mode.
> > >
> > > Signed-off-by: Luca Weiss <luca@xxxxxxxxx>
> >
> > Thanks, applied, but... I may remove it again.
> >
> > > +++ b/drivers/leds/leds-sgm3140.c
> > > @@ -0,0 +1,320 @@
> > > +// SPDX-License-Identifier: GPL-2.0
> >
> > Would you consider GPL-2+?
>
> I don't really have a preference either way but GPL-2.0-or-later is fine for
> me.
>
> > > +#if IS_ENABLED(CONFIG_V4L2_FLASH_LED_CLASS)
> > > +static void sgm3140_init_v4l2_flash_config(struct sgm3140 *priv,
> >
> > Ok.
> >
> > > +static int sgm3140_probe(struct platform_device *pdev)
> > > +{
> >
> > ...
> >
> > > +	led_cdev->brightness_set_blocking = sgm3140_brightness_set;
> > > +	led_cdev->max_brightness = LED_ON;
> >
> > Don't do this, unless you really have 255 levels of brightness.
>
> LED_ON is 1, so the brightness available is 0 - 1.
>
> > > +	/* Create V4L2 Flash subdev */
> > > +	priv->v4l2_flash = v4l2_flash_init(&pdev->dev,
> > > +					   child_node,
> > > +					   fled_cdev, NULL,
> > > +					   &v4l2_sd_cfg);
> > > +	if (IS_ERR(priv->v4l2_flash)) {
> >
> > Does this need some #ifdef guards?
>
> v4l2_flash_init has a NULL-returning version when CONFIG_V4L2_FLASH_LED_CLASS
> is not defined (see https://elixir.bootlin.com/linux/latest/source/include/
> media/v4l2-flash-led-class.h#L166 )

Correct.

> > > +		ret = PTR_ERR(priv->v4l2_flash);
> > > +		goto err;
> > > +	}
> > > +
> > > +	return ret;
> >
> > Should this return 0?
>
> ret should be 0 here, so it shouldn't matter much.
>
> > > +err:
> > > +	fwnode_handle_put(child_node);
> > > +	return ret;
> > > +}
> >
> > Does non-error path needs handle_put, too?
>
> I don't think so, I'm passing child_node to v4l2_flash_init which then saves
> the pointer to v4l2_subdev->fwnode.
>
> The devm_led_classdev_flash_register_ext function also seems to store the
> pointer (led_cdev->dev->fwnode = init_data->fwnode; in
> led_classdev_register_ext)

The node needs to be held only during parsing, so you
have to call fwnode_handle_put() for both paths.

--
Best regards,
Jacek Anaszewski