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Thu, 22 Oct 2026 14:48:43 -0700 (PDT) Received: from Biostar-A520MT ([187.94.15.233]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-5ec13deaba5sm443786e0c.1.2026.10.22.14.48.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Oct 2026 14:48:42 -0700 (PDT) From: Breno Rodrigues Alves To: Jonathan Corbet Cc: linux@armlinux.org.uk, Bart Van Assche , James.Bottomley@HansenPartnership.com, mkp@kernel.org, linux-arm-kernel@lists.infradead.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Breno Rodrigues Alves Subject: Re: [PATCH v4] scsi: arm: Convert acornscsi-io.S to C Date: Thu, 22 Oct 2026 18:48:15 -0300 Message-ID: <20261022214815.86306-1-breno3011alves@gmail.com> X-Mailer: git-send-email 2.56.0 In-Reply-To: <871p9h1kc7.fsf@trenco.lwn.net> References: <20261022183658.58090-1-breno3011alves@gmail.com> <20261022185224.60700-1-breno3011alves@gmail.com> <20261022185224.60700-2-breno3011alves@gmail.com> <871p9h1kc7.fsf@trenco.lwn.net> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Jonathan, Fair question - the change is a conversion, and I do not have a RiscPC with an Acorn SCSI card to test on real hardware. Here is what I did test: 1. Userspace unit test with a mocked MMIO layer I built a small harness that compiles acornscsi-io.c unmodified against stub and headers. The stubs map readl()/writel()/writeb() onto a byte-addressable "card" buffer and a plain userspace memory buffer. For each transfer length L in {0, 2, 4, 8, 16, 32, 64, 100, 512, 1000}: - __acornscsi_in: I filled the "card" with L bytes of a known pattern (each 32-bit card word carrying one 16-bit halfword in the low half, garbage in the high half) and verified that the output buffer matched the pattern byte-for-byte. - __acornscsi_out: I filled a userspace buffer with a known pattern, called the function, and verified that each 32-bit card word held the expected halfword duplicated in both halves. All 20 cases pass. This is the harness that caught the two issues the sashiko bot later reported independently - it is not just a smoke test. 2. Cross-compile for the target Built with arm-linux-gnueabi-gcc on rpc_defconfig with CONFIG_SCSI_ACORNSCSI_3=m. The module links cleanly (acornscsi_mod.ko), and nm on acornscsi-io.o shows: 00000000 T __acornscsi_in 00000104 T __acornscsi_out objdump on the resulting object shows that the alignment step compiles to "bic sl, r0, #3", matching the original assembly's "bic r0, r0, #3". 3. Apply to a clean tree and rebuild Copied the tree, git reset --hard to the parent commit, applied the patch with "git am". It applies cleanly; re-running the same compile command produces the same object. This confirms the patch file itself is intact and does not depend on my working tree state. 4. checkpatch.pl --strict --no-tree on the patch itself Reports 0 errors, 0 warnings (with FILE_PATH_CHANGES ignored, as drivers/scsi/arm/ is already covered by MAINTAINERS). What I did NOT test: - Real hardware. I do not have an Acorn RiscPC or the SCSI expansion card. The unit test proves equivalence with the original assembly semantics, but it cannot prove that the semantics match the actual hardware - only that the C version does the same thing the assembly did. - Odd transfer lengths through acornscsi.c. All current callers pass even lengths, so the trailing-byte path is only exercised by the unit test, not by the driver end-to-end. - Interrupt handling under load. This is unchanged by the patch (the IRQ path is untouched), so I did not add specific coverage. If there is a specific test or configuration you would like me to run, please let me know. Breno