linux-kernel - Re: [PATCH v2] media: vimc: fla: Add virtual flash subdevice

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Date:   Sat, 28 Sep 2019 14:02:09 -0300
From:   Lucas Magalhães <lucmaga@...il.com>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Helen Koike <helen.koike@...labora.com>,
        edusbarretto@...il.com, lkcamp@...ts.libreplanetbr.org
Subject: Re: [PATCH v2] media: vimc: fla: Add virtual flash subdevice

Hi Hans,

Thanks for the review. Sorry about the style mistakes, will be careful
next time.
Just a couple of questions.

On Fri, Sep 20, 2019 at 8:32 AM Hans Verkuil <hverkuil@...all.nl> wrote:
>
> > +static int vimc_fla_s_ctrl(struct v4l2_ctrl *c)
> > +{
> > +
> > +     struct vimc_fla_device *vfla =
> > +             container_of(c->handler, struct vimc_fla_device, hdl);
> > +
> > +     switch (c->id) {
> > +     case V4L2_CID_FLASH_LED_MODE:
> > +             vfla->led_mode = c->val;
> > +             return 0;
> > +     case V4L2_CID_FLASH_STROBE_SOURCE:
> > +             vfla->strobe_source = c->val;
> > +             return 0;
> > +     case V4L2_CID_FLASH_STROBE:
> > +             if (vfla->led_mode != V4L2_FLASH_LED_MODE_FLASH ||
> > +                 vfla->strobe_source != V4L2_FLASH_STROBE_SOURCE_SOFTWARE){
> > +                     return -EILSEQ;
> > +             }
> > +             vfla->is_strobe = true;
> > +             vfla->kthread = kthread_run(vimc_fla_strobe_thread, vfla, "vimc-flash thread");
>
> What if the thread is already running?
>
> I wonder what existing flash drivers do if V4L2_CID_FLASH_STROBE is called
> repeatedly. Perhaps returning EBUSY if strobe is still active makes sense here.
>
> It would also be a nice feature if keeping the strobe on for more than X seconds
> would create a V4L2_FLASH_FAULT_LED_OVER_TEMPERATURE fault.
>
How would you expect this? At this point I will never cross the maximum timeout
configured. I don't expect a driver to fail if I set a value within
the configuration
borders.

> > +     v4l2_ctrl_new_std_menu(&vfla->hdl, &vimc_fla_ctrl_ops,
> > +                            V4L2_CID_FLASH_LED_MODE,
> > +                            V4L2_FLASH_LED_MODE_TORCH, ~0x7,
> > +                            V4L2_FLASH_LED_MODE_NONE);
> > +     v4l2_ctrl_new_std_menu(&vfla->hdl, &vimc_fla_ctrl_ops,
> > +                            V4L2_CID_FLASH_STROBE_SOURCE, 0x1, ~0x3,
> > +                            V4L2_FLASH_STROBE_SOURCE_SOFTWARE);
> > +     v4l2_ctrl_new_std(&vfla->hdl, &vimc_fla_ctrl_ops,
> > +                       V4L2_CID_FLASH_STROBE, 0, 0, 0, 0);
> > +     v4l2_ctrl_new_std(&vfla->hdl, &vimc_fla_ctrl_ops,
> > +                       V4L2_CID_FLASH_STROBE_STOP, 0, 0, 0, 0);
> > +     v4l2_ctrl_new_std(&vfla->hdl, &vimc_fla_ctrl_ops,
> > +                       V4L2_CID_FLASH_TIMEOUT, 0,
> > +                       VIMC_FLASH_TIMEOUT_MAX,
> > +                       VIMC_FLASH_TIMEOUT_STEP,
> > +                       VIMC_FLASH_TIMEOUT_STEP);
> > +     v4l2_ctrl_new_std(&vfla->hdl, &vimc_fla_ctrl_ops,
> > +                       V4L2_CID_FLASH_TORCH_INTENSITY, 0, 255, 1, 255);
> > +     v4l2_ctrl_new_std(&vfla->hdl, &vimc_fla_ctrl_ops,
> > +                       V4L2_CID_FLASH_INTENSITY, 0, 255, 1, 255);
> > +     v4l2_ctrl_new_std(&vfla->hdl, &vimc_fla_ctrl_ops,V4L2_CID_FLASH_INDICATOR_INTENSITY
> > +                       V4L2_CID_FLASH_INDICATOR_INTENSITY, 0, 255, 1, 255);
>
> Can you look at existing flash drivers and copy the min/max/step/def values?
>
> The values here are rather arbitrary. It would be nice if it was a bit more
> realistic.

I didn't found any driver implementing
V4L2_CID_FLASH_INDICATOR_INTENSITY. Do you have
any examples for this? For the other ones I'm copying the lm3646 for
the other ones.

Regards,
Lucas