Re: [PATCHv13 09/28] v4l2-ctrls: prepare internal structs for request API

[Mauro Carvalho Chehab <mchehab+samsung@kernel.org>]

Em Thu,  3 May 2018 16:52:59 +0200
Hans Verkuil <hverkuil@xs4all.nl> escreveu:

> From: Hans Verkuil <hans.verkuil@cisco.com>
> 
> Embed and initialize a media_request_object in struct v4l2_ctrl_handler.
> 
> Add a p_req field to struct v4l2_ctrl_ref that will store the
> request value.
> 
> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
> Signed-off-by: Alexandre Courbot <acourbot@chromium.org>
> ---
>  drivers/media/v4l2-core/v4l2-ctrls.c | 1 +
>  include/media/v4l2-ctrls.h           | 7 +++++++
>  2 files changed, 8 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index aa1dd2015e84..d09f49530d9e 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -1880,6 +1880,7 @@ int v4l2_ctrl_handler_init_class(struct v4l2_ctrl_handler *hdl,
>  				      sizeof(hdl->buckets[0]),
>  				      GFP_KERNEL | __GFP_ZERO);
>  	hdl->error = hdl->buckets ? 0 : -ENOMEM;
> +	media_request_object_init(&hdl->req_obj);
>  	return hdl->error;
>  }
>  EXPORT_SYMBOL(v4l2_ctrl_handler_init_class);
> diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
> index d26b8ddebb56..76352eb59f14 100644
> --- a/include/media/v4l2-ctrls.h
> +++ b/include/media/v4l2-ctrls.h
> @@ -20,6 +20,7 @@
>  #include <linux/list.h>
>  #include <linux/mutex.h>
>  #include <linux/videodev2.h>
> +#include <media/media-request.h>
>  
>  /* forward references */
>  struct file;
> @@ -249,6 +250,8 @@ struct v4l2_ctrl {
>   *		``prepare_ext_ctrls`` function at ``v4l2-ctrl.c``.
>   * @from_other_dev: If true, then @ctrl was defined in another
>   *		device than the &struct v4l2_ctrl_handler.
> + * @p_req:	The request value. Only used if the control handler
> + *		is bound to a media request.

Could you please better elaborate the description of this field?

I read this patch dozen times to understand what you meant by
"request value", as I would be expecting here a "media_request_"
object or something similar. Instead, what you meant to say is that
@p_req will be used to cache the data passed via a request API call,
while the request is not handled yet, right?


>   *
>   * Each control handler has a list of these refs. The list_head is used to
>   * keep a sorted-by-control-ID list of all controls, while the next pointer
> @@ -260,6 +263,7 @@ struct v4l2_ctrl_ref {
>  	struct v4l2_ctrl *ctrl;
>  	struct v4l2_ctrl_helper *helper;
>  	bool from_other_dev;
> +	union v4l2_ctrl_ptr p_req;
>  };
>  
>  /**
> @@ -283,6 +287,8 @@ struct v4l2_ctrl_ref {
>   * @notify_priv: Passed as argument to the v4l2_ctrl notify callback.
>   * @nr_of_buckets: Total number of buckets in the array.
>   * @error:	The error code of the first failed control addition.
> + * @req_obj:	The &struct media_request_object, used to link into a
> + *		&struct media_request.

I would document that there is kref is inside @req_obj, as we can't
add another kref here later.

>   */
>  struct v4l2_ctrl_handler {
>  	struct mutex _lock;
> @@ -295,6 +301,7 @@ struct v4l2_ctrl_handler {
>  	void *notify_priv;
>  	u16 nr_of_buckets;
>  	int error;
> +	struct media_request_object req_obj;
>  };
>  
>  /**



Thanks,
Mauro