Re: [PATCH RFC v2 2/3] media: added managed v4l2 control initialization

Laurent Pinchart
2013-05-15T11:32:34Z

Hi Andrzej,

Thank you for the patch.

On Monday 13 May 2013 10:34:45 Andrzej Hajda wrote:
> This patch adds managed versions of initialization
> and cleanup functions for v4l2 control handler.
>
> Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
> Reviewed-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> ---
> v2:
> - added missing struct device forward declaration,
> - corrected few comments
> ---
> drivers/media/v4l2-core/v4l2-ctrls.c | 48 +++++++++++++++++++++++++++++++
> include/media/v4l2-ctrls.h | 31 ++++++++++++++++++++++
> 2 files changed, 79 insertions(+)
>
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c
> b/drivers/media/v4l2-core/v4l2-ctrls.c index ebb8e48..69c9b95 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -1421,6 +1421,54 @@ void v4l2_ctrl_handler_free(struct v4l2_ctrl_handler
> *hdl) }
> EXPORT_SYMBOL(v4l2_ctrl_handler_free);
>
> +static void devm_v4l2_ctrl_handler_release(struct device *dev, void *res)
> +{
> + struct v4l2_ctrl_handler **hdl = res;
> +
> + v4l2_ctrl_handler_free(*hdl);
> +}
> +
> +int devm_v4l2_ctrl_handler_init(struct device *dev,
> + struct v4l2_ctrl_handler *hdl,
> + unsigned nr_of_controls_hint)
> +{
> + struct v4l2_ctrl_handler **dr;
> + int rc;
> +
> + dr = devres_alloc(devm_v4l2_ctrl_handler_release, sizeof(*dr),
> + GFP_KERNEL);
> + if (!dr)
> + return -ENOMEM;
> +
> + rc = v4l2_ctrl_handler_init(hdl, nr_of_controls_hint);
> + if (rc) {
> + devres_free(dr);
> + return rc;
> + }
> +
> + *dr = hdl;
> + devres_add(dev, dr);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(devm_v4l2_ctrl_handler_init);
> +
> +static int devm_v4l2_ctrl_handler_match(struct device *dev, void *res,
> + void *data)
> +{
> + struct v4l2_ctrl_handler **this = res, **hdl = data;
> +
> + return *this == *hdl;
> +}
> +
> +void devm_v4l2_ctrl_handler_free(struct device *dev,
> + struct v4l2_ctrl_handler *hdl)
> +{
> + WARN_ON(devres_release(dev, devm_v4l2_ctrl_handler_release,
> + devm_v4l2_ctrl_handler_match, &hdl));
> +}
> +EXPORT_SYMBOL_GPL(devm_v4l2_ctrl_handler_free);

I expect very few drivers to actually need devm_v4l2_ctrl_handler_free(), if
any at all. Do you have a use case for that function at the moment ? If not,
what about removing it for now and adding it later when (if) needed ?

> +
> /* For backwards compatibility: V4L2_CID_PRIVATE_BASE should no longer
> be used except in G_CTRL, S_CTRL, QUERYCTRL and QUERYMENU when dealing
> with applications that do not use the NEXT_CTRL flag.
> diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
> index 7343a27..1986b90 100644
> --- a/include/media/v4l2-ctrls.h
> +++ b/include/media/v4l2-ctrls.h
> @@ -25,6 +25,7 @@
> #include <linux/videodev2.h>
>
> /* forward references */
> +struct device;
> struct file;
> struct v4l2_ctrl_handler;
> struct v4l2_ctrl_helper;
> @@ -306,6 +307,36 @@ int v4l2_ctrl_handler_init_class(struct
> v4l2_ctrl_handler *hdl, */
> void v4l2_ctrl_handler_free(struct v4l2_ctrl_handler *hdl);
>
> +/*
> + * devm_v4l2_ctrl_handler_init - managed control handler initialization
> + *
> + * @dev: Device the @hdl belongs to.
> + * @hdl: The control handler.
> + * @nr_of_controls_hint: A hint of how many controls this handler is
> + * expected to refer to.
> + *
> + * This is a managed version of v4l2_ctrl_handler_init. Handler initialized
> with + * this function will be automatically cleaned up on driver detach. +
> *
> + * If an handler initialized with this function needs to be cleaned up
> + * separately, devm_v4l2_ctrl_handler_free() must be used.
> + */
> +int devm_v4l2_ctrl_handler_init(struct device *dev,
> + struct v4l2_ctrl_handler *hdl,
> + unsigned nr_of_controls_hint);
> +
> +/**
> + * devm_v4l2_ctrl_handler_free - managed control handler free
> + *
> + * @dev: Device the @hdl belongs to.
> + * @hdl: Handler to be cleaned up.
> + *
> + * This function should be used to manual free of an control handler
> + * initialized with devm_v4l2_ctrl_handler_init().
> + */
> +void devm_v4l2_ctrl_handler_free(struct device *dev,
> + struct v4l2_ctrl_handler *hdl);
> +
> /** v4l2_ctrl_handler_setup() - Call the s_ctrl op for all controls
> belonging * to the handler to initialize the hardware to the current
> control values. * @hdl: The control handler.
--
Regards,

Laurent Pinchart