linux-kernel - [PATCH] spidev: Make probe to fail early if a spidev compatible is used

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Message-Id: <20211109225920.1158920-1-javierm@redhat.com>
Date:   Tue,  9 Nov 2021 23:59:20 +0100
From:   Javier Martinez Canillas <javierm@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Mark Brown <broonie@...nel.org>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, linux-spi@...r.kernel.org,
        Javier Martinez Canillas <javierm@...hat.com>
Subject: [PATCH] spidev: Make probe to fail early if a spidev compatible is used

Some Device Trees don't use a real device name in the compatible string
for SPI devices nodes, abusing the fact that the spidev driver name is
used to match as a fallback when a SPI device ID table is not defined.

But since commit 6840615f85f6 ("spi: spidev: Add SPI ID table") a table
for SPI device IDs was added to the driver breaking the assumption that
these DTs were relying on.

There has been a warning message for some time since commit 956b200a846e
("spi: spidev: Warn loudly if instantiated from DT as "spidev""), making
quite clear that this case is not really supported by the spidev driver.

Since these devices won't match anyways after the mentioned commit, there
is no point to continue if an spidev compatible is used. Let's just make
the driver probe to fail early.

Signed-off-by: Javier Martinez Canillas <javierm@...hat.com>
---

This patch has only been built tested. I'm posting after a conversation
with Mark and Uwe on IRC.

Best regards,
Javier

 drivers/spi/spidev.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git drivers/spi/spidev.c drivers/spi/spidev.c
index 1bd73e322b7b..4cfa250f16d8 100644
--- drivers/spi/spidev.c
+++ drivers/spi/spidev.c
@@ -751,9 +751,10 @@ static int spidev_probe(struct spi_device *spi)
 	 * compatible string, it is a Linux implementation thing
 	 * rather than a description of the hardware.
 	 */
-	WARN(spi->dev.of_node &&
-	     of_device_is_compatible(spi->dev.of_node, "spidev"),
-	     "%pOF: buggy DT: spidev listed directly in DT\n", spi->dev.of_node);
+	if (spi->dev.of_node && of_device_is_compatible(spi->dev.of_node, "spidev")) {
+		dev_err(&spi->dev, "spidev listed directly in DT is not supported\n");
+		return -EINVAL;
+	}

 	spidev_probe_acpi(spi);

-- 
2.33.1