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

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Date:   Mon, 9 Sep 2019 20:00:26 -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
Subject: Re: [PATCH] media: vimc: fla: Add virtual flash subdevice

Hi Hans,
Thanks for the review. I fixed most of the issues you found. Just have
the question below.

On Mon, Sep 2, 2019 at 9:04 AM Hans Verkuil <hverkuil@...all.nl> wrote:
>
> > +
> > +int vimc_fla_add(struct vimc_device *vimc, struct vimc_ent_config *vcfg)
> > +{
> > +     struct v4l2_device *v4l2_dev = &vimc->v4l2_dev;
> > +     struct vimc_fla_device *vfla;
> > +     int ret;
> > +
> > +     /* Allocate the vfla struct */
> > +     vfla = kzalloc(sizeof(*vfla), GFP_KERNEL);
> > +     if (!vfla)
> > +             return -ENOMEM;
> > +
> > +     v4l2_ctrl_handler_init(&vfla->hdl, 4);
> > +
> > +     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, 1, 10, 1, 10);
> > +     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, 0, 255, 1, 255);
> > +     v4l2_ctrl_new_std(&vfla->hdl, &vimc_fla_ctrl_ops,
> > +                       V4L2_CID_FLASH_STROBE_STATUS, 0, 0, 0, 0);
>
> It would be nice if this would actually reflect the actual strobe status.
>
Regarding the strobe status I was reading the code and find out that
V4L2_CID_FLASH_STROBE_STATUS is a V4L2_CTRL_FLAG_READ_ONLY
but it's not a V4L2_CTRL_FLAG_VOLATILE. I found this intriguing. How an
I suppose to get it if its not volatile? As I understood it changes over time
if the strobe starts and the timeout expire, isn't it? Shouldn't it be volatile
if so?

I've already made a simple implementation were V4L2_CID_FLASH_STROBE_STATUS
returns after calling V4L2_CID_FLASH_STROBE and becomes false after the timeout
time passes.

Thanks!