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>

diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
index b367d479d6b3b77b0bf3b5cf68c0a8c46f5ad5fb..554c591e1113310fd8926ebc2cbc4e124bd9f109 100644 (file)
--- a/drivers/media/v4l2-core/v4l2-common.c
+++ b/drivers/media/v4l2-core/v4l2-common.c
@@ -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
 
 /*

diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
index 5c0a7f6b5bb611d96106ae89ec9bfdc43c46b492..f8b1faced79c863ff2ab0f700ee828ef9c101625 100644 (file)
--- a/include/media/v4l2-common.h
+++ b/include/media/v4l2-common.h
@@ -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,