Re: [PATCH 2/2] leds: rt8515: Add Richtek RT8515 LED driver

[Linus Walleij <linus.walleij@linaro.org>]

Hi Jakub!

thanks for the review. I fixed all comments but I have a problem
with the below:

On Thu, Aug 13, 2020 at 11:04 PM Jacek Anaszewski
<jacek.anaszewski@gmail.com> wrote:
> On 8/12/20 11:07 AM, Linus Walleij wrote:

> > +     /* Init flash intensity setting */
> > +     s = &v4l2_sd_cfg->intensity;
> > +     s->min = 0;
> > +     s->max = rt->fled.led_cdev.max_brightness;
> > +     s->step = 1;
>
> struct v4l2_flash_config's intensity property tells V4L2 flash framework
> how to convert LED class brightness levels to microamperes used by
> the V4L2 flash subdevice.
>
> See max77693_init_v4l2_flash_config() in drivers/leds/leds-max77693.c
> for a reference.

I understand, but I'm a bit of lost here, because I do not have
any datsheet for the Richtek RT8515. The outoftree code
that exists for example for Asus Zenfone:
https://github.com/ZenfoneArea/android_kernel_asus_zenfone5/blob/master/linux/modules/camera/drivers/media/i2c/rt8515.c

The intensity is set to min/max in percent
(0-100%) so the numerals 1-100 step 1 so
the same as the brightness.

Is the V4L2 API such defined that if you don't know
what microamperes that correspond to a certain setting
it is better to simply not implement it? I can certainly
remove it.

I don't quite understand why V4L2 needs to control this
in uA but I suppose they have a good reason. It however
creates a really high bar for out-of-tree code from
non-cooperative vendors. I'll try to send a mail to
Richtek and ask for the datasheet though, stranger things
have happened.

Yours,
Linus Walleij