On SPI device probe, the core will call spi_setup in spi_add_device
before the corresponding driver was probed. When this happens, the
bits_per_word member of the device is not yet set by the driver,
resulting in the default being set to 8 bits-per-word.

However some controllers do not support 8 bits-per-word at all, which
results in a failure when checking the bits-per-word validity.

In order to support these devices, skip the bits-per-word validity
check when it is not explicitly provided by drivers.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
---
 drivers/spi/spi.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 2e6d6bbeb784..563a56ce34a0 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -3518,13 +3518,18 @@ int spi_setup(struct spi_device *spi)
 		return -EINVAL;
 	}
 
-	if (!spi->bits_per_word)
+	if (!spi->bits_per_word) {
 		spi->bits_per_word = 8;
-
-	status = __spi_validate_bits_per_word(spi->controller,
-					      spi->bits_per_word);
-	if (status)
-		return status;
+	} else {
+		/*
+		 * Some controllers may not support the default 8 bits-per-word
+		 * so only perform the check when this is explicitly provided.
+		 */
+		status = __spi_validate_bits_per_word(spi->controller,
+						      spi->bits_per_word);
+		if (status)
+			return status;
+	}
 
 	if (spi->controller->max_speed_hz &&
 	    (!spi->max_speed_hz ||
-- 
2.35.1

On Tue, 12 Apr 2022 14:22:07 +0200, Paul Kocialkowski wrote:
> On SPI device probe, the core will call spi_setup in spi_add_device
> before the corresponding driver was probed. When this happens, the
> bits_per_word member of the device is not yet set by the driver,
> resulting in the default being set to 8 bits-per-word.
> 
> However some controllers do not support 8 bits-per-word at all, which
> results in a failure when checking the bits-per-word validity.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: core: Only check bits_per_word validity when explicitly provided
      commit: b3fe2e516741368a643d79527ebccfe557217a53

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark