[PATCH v3 0/2] spi: unoptimize message when queuing it fails

[Joseph CT Chan <jctchan@gmail.com>]

From: Joseph CT Chan <josephctchan@google.com>

Hi Mark,

spi_async() and spi_sync() optimize a message before they queue it. If
queuing fails, the message is never finalized, so the split transfers
and the controller's optimize state leak and the message stays marked
as optimized. This happens with -EBUSY while another device holds
spi_bus_lock() (for example mmc_spi), with a stopped queue, and with an
error from a legacy transfer() callback. Patch 1 unoptimizes the message
on those error paths, and patch 2 adds KUnit tests for them.

Tested with KUnit using --kunitconfig=drivers/spi on ARCH=um and on
x86_64 under QEMU: the 7 new cases and the 4 existing DMA cases pass
with patch 1, and the 3 queue error cases fail without it. Not tested
on hardware.

Changes in v3:
- Rebased on spi/for-7.5.
- Patch 2: include drivers/spi/tests unconditionally from
  drivers/spi/Makefile instead of adding a second conditional line, as
  you suggested.
- Patch 2: add the test to the existing drivers/spi/.kunitconfig, which
  also runs the DMA tests, instead of adding a new one.

Changes in v2:
- Split out of the v1 14-patch series, as David suggested.
- Patch 1: added David's Reviewed-by.
- Patch 2: inject errors through the fake controller's transfer()
  callback instead of mem_ops, use designated initializers, and trim
  the comments.
- Moved the AI assistance note from an Assisted-by tag into the commit
  message.

v2: https://lore.kernel.org/linux-spi/20261103224753.3610049-1-jctchan@gmail.com/
v1: https://lore.kernel.org/all/20261102163023.2574632-1-jctchan@gmail.com/

Walkthrough of the bug and the tests:
https://gist.github.com/joectchan/9a14b5e6facb75058ebc5a6ff1757131

Please consider this patch series for the next merge window.

Thanks,
Joseph

Joseph CT Chan (2):
  spi: unoptimize message when queuing it fails
  spi: add KUnit tests for message optimize state on queue errors

 drivers/spi/.kunitconfig           |   1 +
 drivers/spi/Kconfig                |  13 ++
 drivers/spi/Makefile               |   2 +-
 drivers/spi/spi.c                  |   7 +
 drivers/spi/tests/Makefile         |   1 +
 drivers/spi/tests/spi-core-kunit.c | 262 +++++++++++++++++++++++++++++
 6 files changed, 285 insertions(+), 1 deletion(-)
 create mode 100644 drivers/spi/tests/spi-core-kunit.c


base-commit: 281521f809f6a6ff406d082293faf1ed3bbfd949
-- 
2.56.0.506.g506a7eabc5-goog