linux-kernel - [PATCH] spi: core: Only check bits_per_word validity when explicitly provided

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Message-Id: <20220412122207.130181-1-paul.kocialkowski@bootlin.com>
Date:   Tue, 12 Apr 2022 14:22:07 +0200
From:   Paul Kocialkowski <paul.kocialkowski@...tlin.com>
To:     linux-spi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Mark Brown <broonie@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Subject: [PATCH] spi: core: Only check bits_per_word validity when explicitly provided

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@...tlin.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