linux-kernel - Re: [PATCH v3 5/7] media: v4l2-core: Add new helper for area controls

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Message-ID: <83a58290-efa2-a4c4-17dc-0380c6b91ce9@xs4all.nl>
Date:   Thu, 29 Aug 2019 12:57:28 +0200
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Ricardo Ribalda Delgado <ribalda@...nel.org>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jacopo Mondi <jacopo@...ndi.org>
Subject: Re: [PATCH v3 5/7] media: v4l2-core: Add new helper for area controls

On 8/23/19 2:37 PM, Ricardo Ribalda Delgado wrote:
> Adding a V4L2_CID_UNIT_CELL_SIZE control requires a lot of boilerplate,
> try to minimize it by adding a new helper.
> 
> Suggested-by: Philipp Zabel <p.zabel@...gutronix.de>
> Signed-off-by: Ricardo Ribalda Delgado <ribalda@...nel.org>
> ---
>  drivers/media/v4l2-core/v4l2-ctrls.c | 25 ++++++++++++++++++++++++-
>  include/media/v4l2-ctrls.h           | 16 ++++++++++++++++
>  2 files changed, 40 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index b3bf458df7f7..33e48f0aec1a 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -2660,7 +2660,6 @@ struct v4l2_ctrl *v4l2_ctrl_new_std_menu_items(struct v4l2_ctrl_handler *hdl,
>  }
>  EXPORT_SYMBOL(v4l2_ctrl_new_std_menu_items);
>  
> -/* Helper function for standard integer menu controls */

Huh?

>  struct v4l2_ctrl *v4l2_ctrl_new_int_menu(struct v4l2_ctrl_handler *hdl,
>  			const struct v4l2_ctrl_ops *ops,
>  			u32 id, u8 _max, u8 _def, const s64 *qmenu_int)
> @@ -2684,6 +2683,30 @@ struct v4l2_ctrl *v4l2_ctrl_new_int_menu(struct v4l2_ctrl_handler *hdl,
>  }
>  EXPORT_SYMBOL(v4l2_ctrl_new_int_menu);
>  
> +static void area_init(const struct v4l2_ctrl *ctrl, u32 idx,
> +		union v4l2_ctrl_ptr ptr)
> +{
> +	memcpy(ptr.p_area, ctrl->priv, sizeof(*ptr.p_area));

This can be used in an array, so you have to honor the idx field.

> +}
> +
> +static const struct v4l2_ctrl_type_ops area_ops = {
> +	.init = area_init,
> +};

This is a standard control type, so just add support for it the std_type_ops
functions.

> +
> +struct v4l2_ctrl *v4l2_ctrl_new_area(struct v4l2_ctrl_handler *hdl,
> +				     const struct v4l2_ctrl_ops *ops,
> +				     u32 id, const struct v4l2_area *area)
> +{
> +	static struct v4l2_ctrl_config ctrl = {
> +		.id = V4L2_CID_UNIT_CELL_SIZE,

This should be set to the passed id, not hardcoded.

> +		.type_ops = &area_ops,

And just drop this line.

> +	};
> +
> +	return v4l2_ctrl_new_custom(hdl, &ctrl, (void *)area);

Don't pass area as a priv pointer. Instead the core will just initialize the
area to some default value (1x1), and then you can call set_ctrl()
after creating the control to set it to the proper value.

The READ_ONLY flag applies to the public API, but the kernel API still has
to be able to change it.

> +}
> +EXPORT_SYMBOL(v4l2_ctrl_new_area);
> +
> +/* Helper function for standard integer menu controls */

This comment doesn't belong here.

>  /* Add the controls from another handler to our own. */
>  int v4l2_ctrl_add_handler(struct v4l2_ctrl_handler *hdl,
>  			  struct v4l2_ctrl_handler *add,
> diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
> index 9a3d11350e67..36f0712ea6dd 100644
> --- a/include/media/v4l2-ctrls.h
> +++ b/include/media/v4l2-ctrls.h
> @@ -669,6 +669,22 @@ struct v4l2_ctrl *v4l2_ctrl_new_int_menu(struct v4l2_ctrl_handler *hdl,
>  					 u32 id, u8 max, u8 def,
>  					 const s64 *qmenu_int);
>  
> +/**
> + * v4l2_ctrl_new_area() - Allocate and initialize a V4L2_CTRL_TYPE_AREA control.
> + *
> + * @hdl:	The control handler.
> + * @ops:	The control ops.
> + * @id:	The control ID.
> + * @area:	The width and height of the area in a struct v4l2_area.

Specifically, this is the initial width and height.

> + *
> + * If the &v4l2_ctrl struct could not be allocated then NULL is returned
> + * and @hdl->error is set to the error code (if it wasn't set already).
> + */
> +
> +struct v4l2_ctrl *v4l2_ctrl_new_area(struct v4l2_ctrl_handler *hdl,
> +				     const struct v4l2_ctrl_ops *ops,
> +				     u32 id, const struct v4l2_area *area);
> +
>  /**
>   * typedef v4l2_ctrl_filter - Typedef to define the filter function to be
>   *	used when adding a control handler.
> 

Regards,

	Hans