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| -rw-r--r-- | Documentation/userspace-api/media/v4l/subdev-formats.rst | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/Documentation/userspace-api/media/v4l/subdev-formats.rst b/Documentation/userspace-api/media/v4l/subdev-formats.rst index 896177c5334f..c9999b929773 100644 --- a/Documentation/userspace-api/media/v4l/subdev-formats.rst +++ b/Documentation/userspace-api/media/v4l/subdev-formats.rst @@ -159,14 +159,18 @@ formats in memory (a raw Bayer image won't be magically converted to JPEG just by storing it to memory), there is no one-to-one correspondence between them. -The media bus pixel codes document parallel formats. Should the pixel data be -transported over a serial bus, the media bus pixel code that describes a -parallel format that transfers a sample on a single clock cycle is used. For -instance, both MEDIA_BUS_FMT_BGR888_1X24 and MEDIA_BUS_FMT_BGR888_3X8 are used -on parallel busses for transferring an 8 bits per sample BGR data, whereas on -serial busses the data in this format is only referred to using -MEDIA_BUS_FMT_BGR888_1X24. This is because there is effectively only a single -way to transport that format on the serial busses. +While the media bus pixel codes are named based on how pixels are +transmitted on parallel buses, serial buses do not define separate +codes. By convention, they use the codes that transfer a sample on a +single clock cycle, and whose bit orders from LSB to MSB correspond to +the order in which colour components are transmitted on the serial bus. +For instance, the MIPI CSI-2 24-bit RGB (RGB888) format uses the +MEDIA_BUS_FMT_RGB888_1X24 media bus code because CSI-2 transmits the +blue colour component first, followed by green and red, and +MEDIA_BUS_FMT_RGB888_1X24 defines the first bit of blue at bit 0. +While used for 24-bit RGB data on parallel buses, the +MEDIA_BUS_FMT_RGB888_3X8 or MEDIA_BUS_FMT_BGR888_1X24 codes must not be +used for CSI-2. Packed RGB Formats ^^^^^^^^^^^^^^^^^^ |