[PATCH v5 0/2] media: Fix CSI2 RGB vs BGR pixel order

[Maxime Ripard <mripard@kernel.org>]

Hi,

Here's an(other [1]) attempt at fixing the current mess due to the
opposite meaning of what v4l2 and the MIPI-CSI2 spec call "RGB". By v4l2
nomenclature, the format CSI calls RGB is actually BGR.

Unfortunately, a handful of CSI transceivers report through RGB media
bus pixel code, which is then understood as V4L2_PIX_FMT_RGB24 by CSI
receivers.

This is made somewhat worse the fact that media bus codes have been made
mostly with parallel busses in mind, and thus the order of pixels wasn't
clearly defined anywhere.

So the v4l2 vs CSI mismatch was confusing (but there's nothing we can do
about it), but the doc didn't really make an attempt at clearing it up
either.

We did have a convention so far though, that about half the affected
drivers were following. 

This series improves the doc, adds the missing media bus codes, and
converts the transceiver drivers to the rightful media bus format.

We'll also need that series [2] from Laurent to fix all the affected
transceivers. 

Let me know what you think,
Maxime

1: https://lore.kernel.org/r/20250606-rpi-unicam-rgb-bgr-fix-v1-1-9930b963f3eb@kernel.org
2: https://lore.kernel.org/r/20250611181528.19542-1-laurent.pinchart@ideasonboard.com

---
Changes in v5:
- Standardize on using RGB888_1X24 for RGB888 instead of BGR888
- Drop the BGR patch
- Drop the csi driver patches in favor of unicam
- Link to v4: https://lore.kernel.org/r/20251013-csi-bgr-rgb-v4-0-55eab2caa69f@kernel.org

Changes in v4:
- Rebased on 6.18-rc1
- Link to v3: https://lore.kernel.org/r/20250917-csi-bgr-rgb-v3-0-0145571b3aa4@kernel.org

Changes in v3:
- Fix typos in commit messages
- use dev_warn_once for deprecation warnings
- Reintroduce dropped unsupported colorspace handling
- Remove unneeded fallthroughs
- Link to v2: https://lore.kernel.org/r/20250911-csi-bgr-rgb-v2-0-e6c6b10c1040@kernel.org

Changes in v2:
- Don't drop RGB, but treat it as deprecated instead.
- Rebase on 6.17-rc5
- Link to v1: https://lore.kernel.org/r/20250612-csi-bgr-rgb-v1-0-dc8a309118f8@kernel.org

---
Maxime Ripard (2):
      media: uapi: Clarify MBUS color component order for serial buses
      media: bcm2835-unicam: Fix RGB format / mbus code association

 .../userspace-api/media/v4l/subdev-formats.rst     | 19 +++++++-----
 drivers/media/platform/broadcom/bcm2835-unicam.c   | 36 +++++++++++++++++++---
 2 files changed, 43 insertions(+), 12 deletions(-)
---
base-commit: 05f7e89ab9731565d8a62e3b5d1ec206485eeb0b
change-id: 20250612-csi-bgr-rgb-b837980c00b3

Best regards,
-- 
Maxime Ripard <mripard@redhat.com>