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media: v4l: Add helper to get number of active lanes via a pad 

Sometimes, users will not use all of the MIPI CSI 2 lanes available when
connecting to the MIPI CSI receiver of their device. Add a helper
function that checks the mbus_config for the device driver to allow
users to define the number of active data lanes through the
get_mbus_config op.

If the driver does not implement this op, fall back to using the maximum
number of lanes available.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Isaac Scott <isaac.scott@ideasonboard.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>
This commit is contained in:
Isaac Scott 2025-10-29 18:03:18 +00:00 committed by Hans Verkuil
parent ca042de648
commit fd3f646e1c
2 changed files with 49 additions and 0 deletions
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29
drivers/media/v4l2-core/v4l2-common.c
View File

@ -573,6 +573,35 @@ s64 v4l2_get_link_freq(const struct media_pad *pad, unsigned int mul,
return v4l2_get_link_freq_ctrl(sd->ctrl_handler, mul, div);
}
EXPORT_SYMBOL_GPL(v4l2_get_link_freq);
int v4l2_get_active_data_lanes(const struct media_pad *pad,
unsigned int max_data_lanes)
{
struct v4l2_mbus_config mbus_config = {};
struct v4l2_subdev *sd;
unsigned int lanes;
int ret;
sd = media_entity_to_v4l2_subdev(pad->entity);
ret = v4l2_subdev_call(sd, pad, get_mbus_config, pad->index,
&mbus_config);
if (ret < 0 && ret != -ENOIOCTLCMD)
return ret;
/* This relies on the mbus_config being zeroed at init time */
lanes = mbus_config.bus.mipi_csi2.num_data_lanes;
if (!lanes)
return max_data_lanes;
if (lanes > max_data_lanes) {
dev_dbg(sd->dev, "Active data lanes (%u) exceeds max (%u)\n",
lanes, max_data_lanes);
return -EINVAL;
}
return lanes;
}
EXPORT_SYMBOL_GPL(v4l2_get_active_data_lanes);
#endif
/*

20
include/media/v4l2-common.h
View File

@ -581,6 +581,26 @@ int v4l2_fill_pixfmt_mp(struct v4l2_pix_format_mplane *pixfmt, u32 pixelformat,
#ifdef CONFIG_MEDIA_CONTROLLER
s64 v4l2_get_link_freq(const struct media_pad *pad, unsigned int mul,
unsigned int div);
/**
* v4l2_get_active_data_lanes - Get number of active data lanes from driver
*
* @pad: The transmitter's media pad.
* @max_data_lanes: The maximum number of active data lanes supported by
* the MIPI CSI link in hardware.
*
* This function is intended for obtaining the number of data lanes that are
* actively being used by the driver for a MIPI CSI-2 device on a given media pad.
* This information is derived from a mbus_config fetched from a device driver
* using the get_mbus_config v4l2_subdev pad op.
*
* Return:
* * >0: Number of active data lanes
* * %-EINVAL: Number of active data lanes is invalid, as it exceeds the maximum
* supported data lanes.
*/
int v4l2_get_active_data_lanes(const struct media_pad *pad,
unsigned int max_data_lanes);
#endif
void v4l2_simplify_fraction(u32 *numerator, u32 *denominator,