[BUG?] b4 shazam applies unrelated patches due to dfblob collision (b4 0.14.3)

["Luca Ceresoli" <luca.ceresoli@bootlin.com>]

Hello b4 developers,

thanks for b4, it is great!

I have a problem (bug?) to report I'm afraid.

While trying to apply a 1-patch series, b4 shazam applied the correct
patch, but:

 - in the output, it listed 22 paches being applied, and none was the
   intended one
 - at the end the branch contained 8 new patches, the first one being the
   intended one
 - it did not pick up the R-by line for the intended patch

Patch and target branch details:

 - appliying on drm-misc-next from
   ssh://git@ssh.gitlab.freedesktop.org/drm/misc/kernel.git currently at
   commit 95d628c9e473 ("drm: rcar-du: lvds: convert to
   of_drm_find_and_get_bridge()")
 - applying the 1-patch seried at
   https://lore.kernel.org/all/20251231-drm-bridge-alloc-getput-drm_of_find_bridge-kdoc-fix-v1-1-193a03f0609c@bootlin.com/

Full log follows.

----------------------8<----------------------
▶ b4 shazam  https://lore.kernel.org/all/20251231-drm-bridge-alloc-getput-drm_of_find_bridge-kdoc-fix-v1-1-193a03f0609c@bootlin.com/
Grabbing thread from lore.kernel.org/all/20251231-drm-bridge-alloc-getput-drm_of_find_bridge-kdoc-fix-v1-1-193a03f0609c@bootlin.com/t.mbox.gz
Checking for newer revisions
Grabbing search results from lore.kernel.org
  Added from v6: 22 patches
  Added from v7: 23 patches
Analyzing 48 messages in the thread
Analyzing 48 code-review messages
Will use the latest revision: v7
You can pick other revisions using the -vN flag
Checking attestation on all messages, may take a moment...
---
  ✓ [PATCH v7 1/22] drm/amd/display: Remove unnecessary SIGNAL_TYPE_HDMI_TYPE_A check
  ✓ [PATCH v7 2/22] drm: Add new general DRM property "color format"
  ✓ [PATCH v7 3/22] drm: Add enum conversions between DRM_COLOR_FORMAT and HDMI_COLORSPACE
  ✓ [PATCH v7 4/22] drm/bridge: Act on the DRM color format property
  ✓ [PATCH v7 5/22] drm/display: hdmi-state-helper: Act on color format DRM property
  ✓ [PATCH v7 6/22] drm/display: hdmi-state-helper: Try subsampling in mode_valid
  ✓ [PATCH v7 7/22] drm/i915: Implement the "color format" DRM property
  ✓ [PATCH v7 8/22] drm/amdgpu: Implement "color format" DRM property
  ✓ [PATCH v7 9/22] drm/rockchip: Add YUV422 output mode constants for VOP2
  ✓ [PATCH v7 10/22] drm/rockchip: vop2: Fix YUV444 output
  ✓ [PATCH v7 11/22] drm/rockchip: vop2: Add RK3576 to the RG swap special case
  ✓ [PATCH v7 12/22] drm/rockchip: vop2: Recognise 10/12-bit YUV422 as YUV formats
  ✓ [PATCH v7 13/22] drm/rockchip: vop2: Set correct output format for RK3576 YUV422
  ✓ [PATCH v7 14/22] drm/bridge: dw-hdmi-qp: Implement atomic_get_output_bus_fmts
  ✓ [PATCH v7 15/22] drm/rockchip: dw_hdmi_qp: Implement "color format" DRM property
  ✓ [PATCH v7 16/22] drm/rockchip: dw_hdmi_qp: Set supported_formats platdata
  ✓ [PATCH v7 17/22] drm/connector: Register color format property on HDMI connectors
    + Reviewed-by: Maxime Ripard <mripard@kernel.org> (✓ DKIM/kernel.org)
  ✓ [PATCH v7 18/22] drm/tests: hdmi: Add tests for the color_format property
  ✓ [PATCH v7 19/22] drm/tests: hdmi: Add tests for HDMI helper's mode_valid
  ✓ [PATCH v7 20/22] drm/tests: edid: Add __maybe_unused attribute to EDID definitions
  ✓ [PATCH v7 21/22] drm/tests: bridge: Add KUnit tests for bridge chain format selection
  ✓ [PATCH v7 22/22] drm/bridge: Document bridge chain format selection
  ---
  ✓ Signed: DKIM/collabora.com
---
Total patches: 22
---
 Base: using specified base-commit dc0b90be8d513256a6594095731a702287f29602
 Deps: looking for dependencies matching 1 patch-ids
Grabbing search results from lore.kernel.org
 Deps: Applying prerequisite patch: [PATCH] drm/bridge: fix kdoc syntax
Applying: drm/bridge: fix kdoc syntax
Applying: drm/amd/display: Remove unnecessary SIGNAL_TYPE_HDMI_TYPE_A check
Applying: drm: Add new general DRM property "color format"
Applying: drm: Add enum conversions between DRM_COLOR_FORMAT and HDMI_COLORSPACE
Applying: drm/bridge: Act on the DRM color format property
Applying: drm/display: hdmi-state-helper: Act on color format DRM property
Applying: drm/display: hdmi-state-helper: Try subsampling in mode_valid
Applying: drm/i915: Implement the "color format" DRM property
Applying: drm/amdgpu: Implement "color format" DRM property
Patch failed at 0009 drm/amdgpu: Implement "color format" DRM property
error: sha1 information is lacking or useless (drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c).
error: could not build fake ancestor
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
▶ git log --oneline  drm-misc/drm-misc-next..
38ebb10f2b83 (HEAD -> drm-misc-next) drm/i915: Implement the "color format" DRM property
01a8c2dc91e0 drm/display: hdmi-state-helper: Try subsampling in mode_valid
50fdbeeed537 drm/display: hdmi-state-helper: Act on color format DRM property
9cb7ad4f0a10 drm/bridge: Act on the DRM color format property
280fd2cb4aa5 drm: Add enum conversions between DRM_COLOR_FORMAT and HDMI_COLORSPACE
7f731f50bf3d drm: Add new general DRM property "color format"
6e173053fa5c drm/amd/display: Remove unnecessary SIGNAL_TYPE_HDMI_TYPE_A check
7a4637bce4f6 drm/bridge: fix kdoc syntax
▶
----------------------8<----------------------

Clue: my colleague Louis found that both the intended patch and some in the
other thread that got applied match the 'dfblob:6dcf8f6d3ec' query on
lore. Maybe the query needs to become more restrictive?

Workaround: I managed to apply the patch 100% correctly by adding the '-v1'
flag to b4. Luckily the other patches matching 'dfblob:6dcf8f6d3ec' are at
different versions. This workaround would not work otherwise, so it is not
really generic.

Best regards,
Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com