Hi Hans,
Thank you for the patch.
On Thursday 08 August 2013 12:58:52 Hans Verkuil wrote:
> The V4L2 specification allows setting volatile controls as that is needed
> if you want to be able to set all controls in one go using
> VIDIOC_S_EXT_CTRLS.
>
> However, such new values should be ignored by the control framework
> since it makes no sense to set a volatile control. While the new value
> will be ignored anyway, it does generate a bogus 'change value' control
> event that should be suppressed.
>
> This patch changes the code to skip setting volatile controls, except for
> one particular case where an autocluster switches to manual mode, because
> that causes the volatile controls to become non-volatile, so the new
> specified values should be retained.
>
> Note that the values returned by VIDIOC_S_CTRL and VIDIOC_S_EXT_CTRLS for
> such skipped volatile controls will be the currently cached values and not
> the latest volatile value. This is something that might have to be fixed
> as well in the future should that be necessary. I think it is overkill,
> though.
This restriction is not documented in Documentation/video4linux/v4l2-
controls.txt. Do we really want to assume that all volatile controls are read-
only and/or inactive ?
> Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
> Cc: pa...@osciak.com
> ---
> drivers/media/v4l2-core/v4l2-ctrls.c | 18 ++++++++++++++++--
> 1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c
> b/drivers/media/v4l2-core/v4l2-ctrls.c index fccd08b..a7cd830 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -2592,6 +2592,7 @@ static int try_set_ext_ctrls(struct v4l2_fh *fh,
> struct v4l2_ctrl_handler *hdl, cs->error_idx = cs->count;
> for (i = 0; !ret && i < cs->count; i++) {
> struct v4l2_ctrl *master;
> + bool set_volatiles = false;
> u32 idx = i;
>
> if (helpers[i].mref == NULL)
> @@ -2627,14 +2628,24 @@ static int try_set_ext_ctrls(struct v4l2_fh *fh,
> struct v4l2_ctrl_handler *hdl, } while (tmp_idx);
> /* If the new value == the manual value, then copy
> the current volatile values. */
> - if (new_auto_val == master->manual_mode_value)
> + if (new_auto_val == master->manual_mode_value) {
> update_from_auto_cluster(master);
> + set_volatiles = true;
> + }
> }
>
> /* Copy the new caller-supplied control values.
> user_to_new() sets 'is_new' to 1. */
> do {
> - ret = user_to_new(cs->controls + idx,
> helpers[idx].ctrl);
> + /*
> + * Skip attempts to set volatile controls since those
> are
> + * ignored anyway. The exception is when an autocluster
> is
> + * switched to manual mode, since in that case the
> specified
> + * 'volatile' controls are actually the new manual
> + * non-volatile values.
> + */
> + if (set_volatiles || !(helpers[idx].ctrl->flags &
> V4L2_CTRL_FLAG_VOLATILE)) + ret =
> user_to_new(cs->controls +
idx,
> helpers[idx].ctrl);
> idx = helpers[idx].next;
> } while (!ret && idx);
>
> @@ -2697,6 +2708,9 @@ static int set_ctrl(struct v4l2_fh *fh, struct
> v4l2_ctrl *ctrl, if (ctrl->type == V4L2_CTRL_TYPE_STRING)
> return -EINVAL;
>
> + if (ctrl->flags & V4L2_CTRL_FLAG_VOLATILE)
> + return 0;
> +
> /* Reset the 'is_new' flags of the cluster */
> for (i = 0; i < master->ncontrols; i++)
> if (master->cluster[i])
--
Regards,
Laurent Pinchart
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