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Sun, 10 May 2026 19:31:53 -0700 (PDT) Received: from localhost.localdomain ([76.32.119.210]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-1327821fd00sm15597932c88.8.2026.05.10.19.31.52 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 10 May 2026 19:31:52 -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 Subject: [PATCH v3] staging: iio: addac: adt7316: document SPI interface switching sequence Date: Mon, 11 May 2026 02:31:27 +0000 Message-Id: <20260511023127.86113-1-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 expected and are ignored. Add a comment to clarify this behavior. Datasheet: https://www.analog.com/en/products/adt7316.html Signed-off-by: Hungyu Lin --- 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 | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/drivers/staging/iio/addac/adt7316-spi.c b/drivers/staging/iio/addac/adt7316-spi.c index f91325d11394..bd92dcddfd91 100644 --- a/drivers/staging/iio/addac/adt7316-spi.c +++ b/drivers/staging/iio/addac/adt7316-spi.c @@ -106,7 +106,17 @@ 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. + * + * During this sequence, the device may still be in I2C mode, + * so SPI transactions may not be recognized and can fail. + * Such errors are expected and are 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