[PATCH v4 24/29] media: v4l2-subdev: Introduce v4l2_subdev_get_frame_desc()

Sakari Ailus
2026-04-08T15:40:29Z

Introduce v4l2_subdev_get_frame_desc() in order to facilitate implementing
drivers that need frame descriptors. If the remote sub-device does not
support frame descriptors, v4l2_subdev_get_frame_desc() creates one (with
a single entry) opportunistically, thus avoiding the need to add frame
descriptor support to sensor drivers the device for which only generates a
single stream, or managing the situation on the caller side.

Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
---
drivers/media/v4l2-core/v4l2-subdev.c | 96 +++++++++++++++++++++++++++
include/media/v4l2-subdev.h | 20 ++++++
2 files changed, 116 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 647587c0499a..40b28e070726 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -20,6 +20,7 @@
#include <linux/version.h>
#include <linux/videodev2.h>

+#include <media/mipi-csi2.h>
#include <media/v4l2-ctrls.h>
#include <media/v4l2-device.h>
#include <media/v4l2-event.h>
@@ -2758,3 +2759,98 @@ void v4l2_subdev_put_privacy_led(struct v4l2_subdev *sd)
#endif
}
EXPORT_SYMBOL_GPL(v4l2_subdev_put_privacy_led);
+
+static int get_mipi_dt_for_mbus(u32 code)
+{
+ switch (code) {
+ case MEDIA_BUS_FMT_BGR888_1X24:
+ return MIPI_CSI2_DT_RGB888;
+ case MEDIA_BUS_FMT_Y8_1X8:
+ case MEDIA_BUS_FMT_SBGGR8_1X8:
+ case MEDIA_BUS_FMT_SGBRG8_1X8:
+ case MEDIA_BUS_FMT_SGRBG8_1X8:
+ case MEDIA_BUS_FMT_SRGGB8_1X8:
+ return MIPI_CSI2_DT_RAW8;
+ case MEDIA_BUS_FMT_Y10_1X10:
+ case MEDIA_BUS_FMT_SBGGR10_1X10:
+ case MEDIA_BUS_FMT_SGBRG10_1X10:
+ case MEDIA_BUS_FMT_SGRBG10_1X10:
+ case MEDIA_BUS_FMT_SRGGB10_1X10:
+ return MIPI_CSI2_DT_RAW10;
+ case MEDIA_BUS_FMT_Y12_1X12:
+ case MEDIA_BUS_FMT_SBGGR12_1X12:
+ case MEDIA_BUS_FMT_SGBRG12_1X12:
+ case MEDIA_BUS_FMT_SGRBG12_1X12:
+ case MEDIA_BUS_FMT_SRGGB12_1X12:
+ return MIPI_CSI2_DT_RAW12;
+ case MEDIA_BUS_FMT_Y14_1X14:
+ case MEDIA_BUS_FMT_SBGGR14_1X14:
+ case MEDIA_BUS_FMT_SGBRG14_1X14:
+ case MEDIA_BUS_FMT_SGRBG14_1X14:
+ case MEDIA_BUS_FMT_SRGGB14_1X14:
+ return MIPI_CSI2_DT_RAW14;
+ case MEDIA_BUS_FMT_Y16_1X16:
+ case MEDIA_BUS_FMT_SBGGR16_1X16:
+ case MEDIA_BUS_FMT_SGBRG16_1X16:
+ case MEDIA_BUS_FMT_SGRBG16_1X16:
+ case MEDIA_BUS_FMT_SRGGB16_1X16:
+ return MIPI_CSI2_DT_RAW16;
+ case MEDIA_BUS_FMT_SBGGR20_1X20:
+ case MEDIA_BUS_FMT_SGBRG20_1X20:
+ case MEDIA_BUS_FMT_SGRBG20_1X20:
+ case MEDIA_BUS_FMT_SRGGB20_1X20:
+ return MIPI_CSI2_DT_RAW20;
+ default:
+ return -EINVAL;
+ }
+}
+
+int v4l2_subdev_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
+ struct v4l2_mbus_frame_desc *desc)
+{
+ struct v4l2_subdev_format subdev_fmt = {
+ .which = V4L2_SUBDEV_FORMAT_ACTIVE,
+ .pad = pad,
+ };
+ int ret;
+
+ if (v4l2_subdev_has_op(sd, pad, get_frame_desc)) {
+ unsigned int type = desc->type;
+
+ ret = v4l2_subdev_call(sd, pad, get_frame_desc, pad, desc);
+
+ if (desc->type != type)
+ return -EINVAL;
+
+ return ret;
+ }
+
+ if (desc->type != V4L2_MBUS_FRAME_DESC_TYPE_PARALLEL &&
+ desc->type != V4L2_MBUS_FRAME_DESC_TYPE_CSI2)
+ return -EINVAL;
+
+ ret = v4l2_subdev_call(sd, pad, get_fmt, NULL, NULL,
+ &subdev_fmt);
+ if (ret)
+ return ret;
+
+ struct v4l2_mbus_frame_desc_entry entry = {
+ .pixelcode = subdev_fmt.format.code,
+ };
+
+ if (desc->type == V4L2_MBUS_FRAME_DESC_TYPE_CSI2) {
+ int dt;
+
+ dt = get_mipi_dt_for_mbus(subdev_fmt.format.code);
+ if (dt < 0)
+ return dt;
+
+ entry.bus.csi2.dt = dt;
+ }
+
+ desc->entry[0] = entry;
+ desc->num_entries = 1;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_subdev_get_frame_desc);
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index 4588992b4417..93b672edd08e 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -2058,4 +2058,24 @@ void v4l2_subdev_notify_event(struct v4l2_subdev *sd,
*/
bool v4l2_subdev_is_streaming(struct v4l2_subdev *sd);

+/**
+ * v4l2_subdev_get_frame_desc() - Get a pad's frame descriptor
+ * @sd: The sub-device
+ * @pad: The number of the pad in @sd from which to obtain the frame descriptor
+ * @desc: A pointer to a frame descriptor, with its type field set
+ *
+ * Obtain a frame descriptor from a sub-device. If the sub-device supports the
+ * get_frame_desc pad operation, its result is returned, just like calling it
+ * directly using v4l2_subdev_call(). If the sub-device driver does not support
+ * it, then one containing a single entry is created using the information from
+ * the sub-device active state, which this function locks for the duration of
+ * the call to obtain it.
+ *
+ * The caller is required to set @desc->type to the expected bus type.
+ *
+ * Return: %0 on success or negative error code on failure.
+ */
+int v4l2_subdev_get_frame_desc(struct v4l2_subdev *sd, unsigned int pad,
+ struct v4l2_mbus_frame_desc *desc);
+
#endif /* _V4L2_SUBDEV_H */
--
2.47.3