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Mon, 11 May 2026 07:07:07 -0700 (PDT) Received: from localhost.localdomain ([76.32.119.210]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2f88847504dsm13699258eec.15.2026.05.11.07.07.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 11 May 2026 07:07:06 -0700 (PDT) From: Hungyu Lin To: jic23@kernel.org, lars@metafoo.de, Michael.Hennerich@analog.com, gregkh@linuxfoundation.org Cc: dlechner@baylibre.com, nuno.sa@analog.com, andy@kernel.org, m32285159@gmail.com, linux-iio@vger.kernel.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, Hungyu Lin , Andy Shevchenko Subject: [PATCH v4] staging: iio: addac: adt7316: document SPI interface switching sequence Date: Mon, 11 May 2026 14:06:41 +0000 Message-Id: <20260511140641.86389-1-dennylin0707@gmail.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The device powers up in I2C mode. Switching to SPI mode requires sending a sequence of SPI writes as described in the datasheet. During this sequence, the device may still be in I2C mode, so SPI transactions may not be recognized and can fail. Such errors are therefore ignored. Add a comment to clarify this behavior. Datasheet: https://www.analog.com/en/products/adt7316.html Reviewed-by: Maxwell Doose Reviewed-by: Andy Shevchenko Signed-off-by: Hungyu Lin --- Changes in v4: - Restore section title in datasheet reference - Adjust wording per Jonathan's suggestion - Add Reviewed-by tags Changes in v3: - Add Datasheet tag - Use datasheet name in code comment Changes in v2: - Add datasheet reference - Add TL;DR note drivers/staging/iio/addac/adt7316-spi.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) diff --git a/drivers/staging/iio/addac/adt7316-spi.c b/drivers/staging/iio/addac/adt7316-spi.c index f91325d11394..1debcc36c1af 100644 --- a/drivers/staging/iio/addac/adt7316-spi.c +++ b/drivers/staging/iio/addac/adt7316-spi.c @@ -106,7 +106,18 @@ static int adt7316_spi_probe(struct spi_device *spi_dev) return -EINVAL; } - /* switch from default I2C protocol to SPI protocol */ + /* + * The device powers up in I2C mode. Switching to SPI mode + * requires sending a sequence of SPI writes as described in + * the datasheet "ADT7316/ADT7317/ADT7318", Rev. B, + * in the "Serial Interface Selection" section. + * + * During this sequence, the device may still be in I2C mode, + * so SPI transactions may not be recognized and can fail. + * Such errors are therefore ignored. + * + * TL;DR: Do not change this! + */ adt7316_spi_write(spi_dev, 0, 0); adt7316_spi_write(spi_dev, 0, 0); adt7316_spi_write(spi_dev, 0, 0); -- 2.34.1