Em Tue, 14 Aug 2018 10:45:57 +0200
Hans Verkuil <hverkuil@xxxxxxxxx> escreveu:
> On 13/08/18 13:07, Mauro Carvalho Chehab wrote:
> > Em Sat, 4 Aug 2018 14:45:08 +0200
> > Hans Verkuil <hverkuil@xxxxxxxxx> escreveu:
> >
> >> If a driver needs to find/inspect the controls set in a request then
> >> it can use these functions.
> >>
> >> E.g. to check if a required control is set in a request use this in the
> >> req_validate() implementation:
> >>
> >> int res = -EINVAL;
> >>
> >> hdl = v4l2_ctrl_request_hdl_find(req, parent_hdl);
> >> if (hdl) {
> >> if (v4l2_ctrl_request_hdl_ctrl_find(hdl, ctrl_id))
> >> res = 0;
> >> v4l2_ctrl_request_hdl_put(hdl);
> >> }
> >> return res;
> >>
> >> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> >> ---
> >> drivers/media/v4l2-core/v4l2-ctrls.c | 25 ++++++++++++++++
> >> include/media/v4l2-ctrls.h | 44 +++++++++++++++++++++++++++-
> >> 2 files changed, 68 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> >> index 86a6ae54ccaa..2a30be824491 100644
> >> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> >> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> >> @@ -2976,6 +2976,31 @@ static const struct media_request_object_ops req_ops = {
> >> .release = v4l2_ctrl_request_release,
> >> };
> >>
> >> +struct v4l2_ctrl_handler *v4l2_ctrl_request_hdl_find(struct media_request *req,
> >> + struct v4l2_ctrl_handler *parent)
> >> +{
> >> + struct media_request_object *obj;
> >> +
> >> + if (WARN_ON(req->state != MEDIA_REQUEST_STATE_VALIDATING &&
> >> + req->state != MEDIA_REQUEST_STATE_QUEUED))
> >> + return NULL;
> >> +
> >> + obj = media_request_object_find(req, &req_ops, parent);
> >> + if (obj)
> >> + return container_of(obj, struct v4l2_ctrl_handler, req_obj);
> >> + return NULL;
> >> +}
> >> +EXPORT_SYMBOL_GPL(v4l2_ctrl_request_hdl_find);
> >> +
> >> +struct v4l2_ctrl *
> >> +v4l2_ctrl_request_hdl_ctrl_find(struct v4l2_ctrl_handler *hdl, u32 id)
> >> +{
> >> + struct v4l2_ctrl_ref *ref = find_ref_lock(hdl, id);
> >> +
> >> + return (ref && ref->req == ref) ? ref->ctrl : NULL;
> >
> > Doesn't those helper functions (including this one) be serialized?
>
> v4l2_ctrl_request_hdl_find() checks the request state to ensure this:
> it is either VALIDATING (then the req_queue_mutex is locked) or QUEUED
> and then it is under control of the driver. Of course, in that case the
> driver should make sure that it doesn't complete the request in the
> middle of calling this function. If a driver does that, then it is a driver
> bug.
Please document it then, as I guess anyone that didn't worked at the
request API patchset wouldn't guess when the driver needs to take
the lock themselves.
>From what I'm understanding, the driver needs to take the lock only
when it is running a code that it is not called from an ioctl.
right?
Thanks,
Mauro
