linux-kernel - [PATCH v2 1/2] iio: adc: ad7124: Don't create more channels than the driver can handle

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Message-ID:  <26b8c3f2f204ca62520f0f3fe1e5173bc9ba3d30.1731404695.git.u.kleine-koenig@baylibre.com>
Date: Mon, 18 Nov 2024 12:19:55 +0100
From: Uwe Kleine-König <u.kleine-koenig@...libre.com>
To: Lars-Peter Clausen <lars@...afoo.de>,
	Michael Hennerich <Michael.Hennerich@...log.com>,
	Jonathan Cameron <jic23@...nel.org>
Cc: linux-iio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/2] iio: adc: ad7124: Don't create more channels than the driver can handle

The ad7124-4 and ad7124-8 both support 16 channel registers and assigns
each channel defined in dt statically such a register. While the driver
could be a bit more clever about this, it currently isn't and specifying
more than 16 channels yields broken behaviour. So just refuse to bind in
this situation.

Fixes: b3af341bbd96 ("iio: adc: Add ad7124 support")
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...libre.com>
---
 drivers/iio/adc/ad7124.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index 749304d38415..4de69bb8653a 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -821,6 +821,16 @@ static int ad7124_parse_channel_config(struct iio_dev *indio_dev,
 	if (!st->num_channels)
 		return dev_err_probe(dev, -ENODEV, "no channel children\n");
 
+	/*
+	 * The driver assigns each logical channel defined in the device tree
+	 * statically one channel register. So only accept 16 such logical
+	 * channels to not treat CONFIG_0 (i.e. the register following
+	 * CHANNEL_15) as an additional channel register. The driver could be
+	 * improved to lift this limitation.
+	 */
+	if (st->num_channels > AD7124_MAX_CHANNELS)
+		return dev_err_probe(dev, -EINVAL, "Too many channels defined\n");
+
 	chan = devm_kcalloc(indio_dev->dev.parent, st->num_channels,
 			    sizeof(*chan), GFP_KERNEL);
 	if (!chan)
-- 
2.45.2