[PATCH v2 00/25] media: v4l2-mem2mem: Reduce cargo-cult

[Laurent Pinchart]

Hello,

The v4l2_m2m_get_vq() function never returns NULL, but many mem2mem
drivers still check its return value and consider NULL as an error. This
may have originated a long time ago from valid checks when
v4l2_m2m_get_vq() could return NULL, with drivers then just copying the
checks. This series attempts to stop the cargo-cult behaviour.

Patch 01/25 starts by explicitly stating in kerneldoc that the
v4l2_m2m_get_vq() function never returns NULL. All the other patches
drop NULL checks from drivers.

I have carefully checked all patched locations in all drivers. They fall
in 3 categories:

- Checks in the VIDIOC_G_FMT, VIDIOC_TRY_FMT and VIDIOC_S_FMT handlers:
  Those may have been added to ensure that the format type has a valid
  value, but that is ensured by the V4L2 ioctl core before calling the
  handlers. The checks can be dropped without a need to replace them
  with proper type checks.

- Checks in the VIDIOC_S_SELECTION handler: The only location where this
  is performed has an explicit type check, so the NULL check can also be
  dropped.

- Checks in other locations where the type parameter to the
  v4l2_m2m_get_vq() function is hardcoded: The hardcoded type is valid,
  so the NULL check can't have been meant to check the type. It can also
  be removed.

There's no dependency between any of those patches so they can be merged
in any order.

Compared to v1, this version drops two more NULL checks, in the Mediatek
vcodec encoder get format handler (09/25) and the Qualcomm iris venc set
format handler (15/25).

Laurent Pinchart (25):
  media: v4l2-mem2mem: Document that v4l2_m2m_get_vq() never returns
    NULL
  media: allgro-dvt: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: meson-g2d: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: amphion: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: coda: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: imagination: e5010: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: m2m-deinterlace: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: mediatek: jpeg: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: mediatek: vcodec: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: dw100: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: imx-jpeg: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: imx-pxp: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: nxp: imx8-isi: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: mx2_emmaprp: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: qcom: iris: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: qcom: venus: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: renesas: fdp1: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: rcar_jpu: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: platform: rga: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: samsung: s5p-g2d: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: samsung: s5p-jpeg: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: stm32: dma2d: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: ti: vpe: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: vicodec: Drop unneeded v4l2_m2m_get_vq() NULL check
  media: vim2m: Drop unneeded v4l2_m2m_get_vq() NULL check

 drivers/media/platform/allegro-dvt/allegro-core.c  |  2 --
 drivers/media/platform/amlogic/meson-ge2d/ge2d.c   |  5 -----
 drivers/media/platform/amphion/vdec.c              |  2 --
 drivers/media/platform/amphion/venc.c              |  2 --
 .../media/platform/chips-media/coda/coda-common.c  |  4 ----
 .../media/platform/imagination/e5010-jpeg-enc.c    |  4 ----
 drivers/media/platform/m2m-deinterlace.c           |  7 -------
 .../media/platform/mediatek/jpeg/mtk_jpeg_core.c   |  7 -------
 .../mediatek/vcodec/decoder/mtk_vcodec_dec.c       |  7 -------
 .../vcodec/decoder/vdec/vdec_av1_req_lat_if.c      |  2 --
 .../vcodec/decoder/vdec/vdec_vp9_req_lat_if.c      |  2 --
 .../mediatek/vcodec/encoder/mtk_vcodec_enc.c       | 14 --------------
 drivers/media/platform/nxp/dw100/dw100.c           |  7 -------
 drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c     |  4 ----
 drivers/media/platform/nxp/imx-pxp.c               |  7 -------
 drivers/media/platform/nxp/imx8-isi/imx8-isi-m2m.c |  2 --
 drivers/media/platform/nxp/mx2_emmaprp.c           |  7 -------
 drivers/media/platform/qcom/iris/iris_vdec.c       |  2 --
 drivers/media/platform/qcom/iris/iris_venc.c       |  2 --
 drivers/media/platform/qcom/venus/vdec.c           |  2 --
 drivers/media/platform/qcom/venus/venc.c           |  2 --
 drivers/media/platform/renesas/rcar_fdp1.c         |  3 ---
 drivers/media/platform/renesas/rcar_jpu.c          |  8 --------
 drivers/media/platform/rockchip/rga/rga.c          |  4 ----
 drivers/media/platform/samsung/s5p-g2d/g2d.c       |  4 ----
 .../media/platform/samsung/s5p-jpeg/jpeg-core.c    |  7 -------
 drivers/media/platform/st/stm32/dma2d/dma2d.c      |  5 -----
 drivers/media/platform/ti/vpe/vpe.c                |  7 -------
 drivers/media/test-drivers/vicodec/vicodec-core.c  |  7 -------
 drivers/media/test-drivers/vim2m.c                 | 12 ------------
 drivers/media/v4l2-core/v4l2-mem2mem.c             | 12 +-----------
 include/media/v4l2-mem2mem.h                       |  3 +++
 32 files changed, 4 insertions(+), 161 deletions(-)


base-commit: 082b86919b7a94de01d849021b4da820a6cb89dc
-- 
Regards,

Laurent Pinchart