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Sat, 02 May 2026 11:16:21 -0700 (PDT) Sender: Guenter Roeck Date: Sat, 2 May 2026 11:16:20 -0700 From: Guenter Roeck To: Tabrez Ahmed Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, shuah@kernel.org, me@brighamcampbell.com, Sashiko Subject: Re: [PATCH v5 1/3] hwmon: (ads7871) Fix endianness bug in 16-bit register reads Message-ID: References: <20260501023530.31160-1-tabreztalks@gmail.com> <20260501023530.31160-2-tabreztalks@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260501023530.31160-2-tabreztalks@gmail.com> On Fri, May 01, 2026 at 08:05:28AM +0530, Tabrez Ahmed wrote: > The ads7871_read_reg16() function relies on spi_w8r16() to read the > 16-bit sensor output. The ADS7871 device transmits the Least Significant > Byte (LSB) first. > > On Little-Endian architectures, spi_w8r16() correctly reconstructs the > 16-bit value. However, on Big-Endian architectures, the byte swapping > causes the first received byte (LSB) to be placed in the most significant > byte of the u16, resulting in corrupted voltage readings. > > Replace spi_w8r16() with a manual spi_write_then_read() into a byte array, > and safely reconstruct the integer using get_unaligned_le16() to ensure > correct behavior across all architectures. Additionally, use a u8 > variable for the command byte to ensure the correct instruction is > transmitted on Big-Endian systems. > > Reported-by: Sashiko > Closes: https://sashiko.dev/#/patchset/20260418034601.90226-1-tabreztalks@gmail.com > Signed-off-by: Tabrez Ahmed Applied. Thanks, Guenter