[PATCH v5 0/7] char: xillybus: Harden driver and improve code quality

[Eli Billauer <eli.billauer@gmail.com>]

This patch set consists of several boundary and sanity checks, gaining
better control of execution flow and fixing minor coding issues. No
difference is expected in the driver's behavior under normal conditions,
except for one change that might improve bandwidth performance
marginally.

Why all of the sudden? These patches are the result of a comprehensive
AI-assisted code review, using Deepseek, Kimi Thinking K2.6, ChatGPT,
and Claude Sonnet 4.6 as plain prompt tools.

I've spent three weeks in what I call a "reverse rubber duck" session,
asking these LLMs to find bugs in the code and following up on different
leads, the vast majority of which turned out to be no more than quack.
Occasionally the points made by AI were valid, and in others, the mere
effort to explain why the remark is wrong to the rubber duck led to
finding real issues.

Almost none of the fixes suggested by AI were even near the actual
corrections in this patch set.

The v1 iteration of this series was rejected due to an error in the
error path. Specifically, the @rc variable was not assigned a value
before a goto statement following a failed allocation. This oversight
was caught during compilation with LLVM=1, but was missed by GCC and the
AI tools used during the review (and myself of course).

All patches are unchanged since v1, except for "Add defensive sanity
checks", which fixes the said error and also makes a couple of minor
adjustments.

The change from v2 to v3 merely consists of adding Assisted-by tags
to the patches as required.

This v4 submission is the response to some of Sashiko's remarks on the
v3 submission:

https://sashiko.dev/#/patchset/20260724094302.50761-1-eli.billauer@gmail.com

Three remarks relate to the patches in these patch set, and have been
corrected accordingly, with Assisted-by tags duly added. Sashiko also
had several other valid remarks which call for additional patches.
These will be submitted once the processing of this patch set is done.

The v5 submission fixes one issue brought up by Sashiko's remarks on v4,
adding a small fix to the "Integer arithmetic improvements" patch.

https://sashiko.dev/#/patchset/20260805093436.59740-1-eli.billauer%40gmail.com

Thanks & regards,
   Eli

Eli Billauer (7):
  char: xillybus: Improve control of execution flow with mutexes
  char: xillybus: Remove duplicate error path code
  char: xillybus: Avoid possible bandwidth inefficiency
  char: xillybus: Use unsigned arithmetic for jiffies differences
  char: xillybus: Integer arithmetic improvements
  char: xillybus: Add defensive sanity checks
  char: xillybus: Ignore and report unsolicited interrupts

 drivers/char/xillybus/xillybus.h       |  3 +
 drivers/char/xillybus/xillybus_class.c | 18 ++++-
 drivers/char/xillybus/xillybus_class.h |  3 +
 drivers/char/xillybus/xillybus_core.c  | 97 ++++++++++++++++++++++----
 drivers/char/xillybus/xillybus_of.c    |  3 +
 drivers/char/xillybus/xillyusb.c       | 65 ++++++++++++-----
 6 files changed, 159 insertions(+), 30 deletions(-)

-- 
2.34.1