Hi Hans,
On Mon, Apr 09, 2018 at 04:20:03PM +0200, Hans Verkuil wrote:
> From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>
> Add media_request_find() to find a request based on the file
> descriptor.
>
> The caller has to call media_request_put() for the returned
> request since this function increments the refcount.
>
> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> ---
> drivers/media/media-request.c | 47 +++++++++++++++++++++++++++++++++++++++++++
> include/media/media-request.h | 10 +++++++++
> 2 files changed, 57 insertions(+)
>
> diff --git a/drivers/media/media-request.c b/drivers/media/media-request.c
> index 27739ff7cb09..02b620c81de5 100644
> --- a/drivers/media/media-request.c
> +++ b/drivers/media/media-request.c
> @@ -207,6 +207,53 @@ static const struct file_operations request_fops = {
> .release = media_request_close,
> };
>
> +/**
> + * media_request_find - Find a request based on the file descriptor
> + * @mdev: The media device
> + * @request: The request file handle
> + *
> + * Find and return the request associated with the given file descriptor, or
> + * an error if no such request exists.
> + *
> + * When the function returns a request it increases its reference count. The
> + * caller is responsible for releasing the reference by calling
> + * media_request_put() on the request.
> + */
> +struct media_request *
> +media_request_find(struct media_device *mdev, int request_fd)
> +{
> + struct file *filp;
> + struct media_request *req;
> +
> + if (!mdev || !mdev->ops || !mdev->ops->req_queue)
> + return ERR_PTR(-EPERM);
> +
> + filp = fget(request_fd);
> + if (!filp)
> + return ERR_PTR(-ENOENT);
> +
> + if (filp->f_op != &request_fops)
> + goto err_fput;
> + req = filp->private_data;
> + media_request_get(req);
As you're holding a reference to filp, you also indirectly have reference
to ref --- you otherwise couldn't access file->private_data either.
Therefore you could move the check for the right mdev before getting a
reference to req, thus simplifying error handling as a result.
> +
> + if (req->mdev != mdev)
> + goto err_kref_put;
> +
> + fput(filp);
> +
> + return req;
> +
> +err_kref_put:
> + media_request_put(req);
> +
> +err_fput:
> + fput(filp);
> +
> + return ERR_PTR(-ENOENT);
> +}
> +EXPORT_SYMBOL_GPL(media_request_find);
> +
> int media_request_alloc(struct media_device *mdev,
> struct media_request_alloc *alloc)
> {
--
Sakari Ailus
e-mail: sakari.ailus@xxxxxx
