[v6,6/8] media: subdev: add locking wrappers to subdev op wrappers

It is common that media drivers call subdev ops in source subdevs, and
pass NULL as the state. This was the way to indicate that the callee
should use the callee's private active state.

E.g.:

v4l2_subdev_call(priv->source_sd, pad, get_fmt, NULL, &sd_fmt);

Now that we have a real subdev active state in the v4l2_subdev struct,
we want the caller to pass a proper state (when available). And
furthermore, the state should be locked.

This would mean changing all the callers, which is the long term goal.

To fix this issue in the short term, let's add an extra wrapper layer to
all v4l2_subdev_call_pad_wrappers which deal with states. These wrappers
handle the state == NULL case by using the locked active state instead
(when available).

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
---
 drivers/media/v4l2-core/v4l2-subdev.c | 42 ++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 7 deletions(-)

On 24/03/2022 09:00, Tomi Valkeinen wrote:
> It is common that media drivers call subdev ops in source subdevs, and
> pass NULL as the state. This was the way to indicate that the callee
> should use the callee's private active state.
> 
> E.g.:
> 
> v4l2_subdev_call(priv->source_sd, pad, get_fmt, NULL, &sd_fmt);
> 
> Now that we have a real subdev active state in the v4l2_subdev struct,
> we want the caller to pass a proper state (when available). And
> furthermore, the state should be locked.
> 
> This would mean changing all the callers, which is the long term goal.
> 
> To fix this issue in the short term, let's add an extra wrapper layer to
> all v4l2_subdev_call_pad_wrappers which deal with states. These wrappers
> handle the state == NULL case by using the locked active state instead
> (when available).
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>

Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Regards,

	Hans

> ---
>  drivers/media/v4l2-core/v4l2-subdev.c | 42 ++++++++++++++++++++++-----
>  1 file changed, 35 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
> index 824424f0a741..d8d1c9ef4dc4 100644
> --- a/drivers/media/v4l2-core/v4l2-subdev.c
> +++ b/drivers/media/v4l2-core/v4l2-subdev.c
> @@ -319,14 +319,42 @@ static int call_get_mbus_config(struct v4l2_subdev *sd, unsigned int pad,
>  	       sd->ops->pad->get_mbus_config(sd, pad, config);
>  }
>  
> +/*
> + * Create state-management wrapper for pad ops dealing with subdev state. The
> + * wrapper handles the case where the caller does not provide the called
> + * subdev's state. This should be removed when all the callers are fixed.
> + */
> +#define DEFINE_STATE_WRAPPER(f, arg_type)                                  \
> +	static int call_##f##_state(struct v4l2_subdev *sd,                \
> +				    struct v4l2_subdev_state *_state,      \
> +				    arg_type *format)                      \
> +	{                                                                  \
> +		struct v4l2_subdev_state *state = _state;                  \
> +		int ret;                                                   \
> +		if (!_state)                                               \
> +			state = v4l2_subdev_lock_and_get_active_state(sd); \
> +		ret = call_##f(sd, state, format);                         \
> +		if (!_state && state)                                      \
> +			v4l2_subdev_unlock_state(state);                   \
> +		return ret;                                                \
> +	}
> +
> +DEFINE_STATE_WRAPPER(get_fmt, struct v4l2_subdev_format);
> +DEFINE_STATE_WRAPPER(set_fmt, struct v4l2_subdev_format);
> +DEFINE_STATE_WRAPPER(enum_mbus_code, struct v4l2_subdev_mbus_code_enum);
> +DEFINE_STATE_WRAPPER(enum_frame_size, struct v4l2_subdev_frame_size_enum);
> +DEFINE_STATE_WRAPPER(enum_frame_interval, struct v4l2_subdev_frame_interval_enum);
> +DEFINE_STATE_WRAPPER(get_selection, struct v4l2_subdev_selection);
> +DEFINE_STATE_WRAPPER(set_selection, struct v4l2_subdev_selection);
> +
>  static const struct v4l2_subdev_pad_ops v4l2_subdev_call_pad_wrappers = {
> -	.get_fmt		= call_get_fmt,
> -	.set_fmt		= call_set_fmt,
> -	.enum_mbus_code		= call_enum_mbus_code,
> -	.enum_frame_size	= call_enum_frame_size,
> -	.enum_frame_interval	= call_enum_frame_interval,
> -	.get_selection		= call_get_selection,
> -	.set_selection		= call_set_selection,
> +	.get_fmt		= call_get_fmt_state,
> +	.set_fmt		= call_set_fmt_state,
> +	.enum_mbus_code		= call_enum_mbus_code_state,
> +	.enum_frame_size	= call_enum_frame_size_state,
> +	.enum_frame_interval	= call_enum_frame_interval_state,
> +	.get_selection		= call_get_selection_state,
> +	.set_selection		= call_set_selection_state,
>  	.get_edid		= call_get_edid,
>  	.set_edid		= call_set_edid,
>  	.dv_timings_cap		= call_dv_timings_cap,