From 8bf3e7a9defcfa889976258919d99fa2e8465189 Mon Sep 17 00:00:00 2001 From: Hungyu Lin Date: Mon, 11 May 2026 14:06:41 +0000 Subject: [PATCH] staging: iio: addac: adt7316: document SPI interface switching sequence 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 Signed-off-by: Jonathan Cameron --- 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);