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Sun, 31 Aug 2025 08:37:53 -0700 (PDT) Received: from localhost ([77.111.118.146]) by smtp.gmail.com with UTF8SMTPSA id d9443c01a7336-24a92f897d8sm38927595ad.24.2025.08.31.08.37.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 31 Aug 2025 08:37:53 -0700 (PDT) From: Mohammad Amin Hosseini To: linux-iio@vger.kernel.org, linux-staging@lists.linux.dev Cc: linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, jic23@kernel.org, lars@metafoo.de, Michael.Hennerich@analog.com, dlechner@baylibre.com, nuno.sa@analog.com, andy@kernel.org, mohammad amin hosseini Subject: [PATCH] staging: iio: adc: ad7816: add mutex to serialize SPI/GPIO operations Date: Sun, 31 Aug 2025 19:07:41 +0330 Message-ID: <20250831153741.8820-1-moahmmad.hosseinii@gmail.com> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: mohammad amin hosseini The ad7816 driver was accessing SPI and GPIO lines without synchronization, which could lead to race conditions when accessed concurrently from multiple contexts. This might result in corrupted readings or inconsistent GPIO states. Introduce an io_lock mutex in the driver structure to serialize: - SPI transactions in ad7816_spi_read() and ad7816_spi_write() - GPIO pin toggling sequences - Updates to device state via sysfs store functions (mode, channel, oti) The mutex ensures proper mutual exclusion and prevents race conditions under concurrent access. Signed-off-by: Mohammad Amin Hosseini --- drivers/staging/iio/adc/ad7816.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) diff --git a/drivers/staging/iio/adc/ad7816.c b/drivers/staging/iio/adc/ad7= 816.c index 4774df778de9..06567d048a6d 100644 --- a/drivers/staging/iio/adc/ad7816.c +++ b/drivers/staging/iio/adc/ad7816.c @@ -50,6 +50,7 @@ struct ad7816_chip_info { u8 oti_data[AD7816_CS_MAX + 1]; u8 channel_id; /* 0 always be temperature */ u8 mode; + struct mutex io_lock; /* Protects SPI transactions and GPIO toggling */ }; =20 enum ad7816_type { @@ -67,13 +68,13 @@ static int ad7816_spi_read(struct ad7816_chip_info *chi= p, u16 *data) int ret; __be16 buf; =20 + mutex_lock(&chip->io_lock); + gpiod_set_value(chip->rdwr_pin, 1); gpiod_set_value(chip->rdwr_pin, 0); ret =3D spi_write(spi_dev, &chip->channel_id, sizeof(chip->channel_id)); - if (ret < 0) { - dev_err(&spi_dev->dev, "SPI channel setting error\n"); - return ret; - } + if (ret < 0) + goto unlock; gpiod_set_value(chip->rdwr_pin, 1); =20 if (chip->mode =3D=3D AD7816_PD) { /* operating mode 2 */ @@ -92,13 +93,13 @@ static int ad7816_spi_read(struct ad7816_chip_info *chi= p, u16 *data) gpiod_set_value(chip->rdwr_pin, 0); gpiod_set_value(chip->rdwr_pin, 1); ret =3D spi_read(spi_dev, &buf, sizeof(*data)); - if (ret < 0) { - dev_err(&spi_dev->dev, "SPI data read error\n"); - return ret; - } + if (ret < 0) + goto unlock; =20 *data =3D be16_to_cpu(buf); =20 +unlock: + mutex_unlock(&chip->io_lock); return ret; } =20 @@ -107,12 +108,13 @@ static int ad7816_spi_write(struct ad7816_chip_info *= chip, u8 data) struct spi_device *spi_dev =3D chip->spi_dev; int ret; =20 + mutex_lock(&chip->io_lock); + gpiod_set_value(chip->rdwr_pin, 1); gpiod_set_value(chip->rdwr_pin, 0); ret =3D spi_write(spi_dev, &data, sizeof(data)); - if (ret < 0) - dev_err(&spi_dev->dev, "SPI oti data write error\n"); =20 + mutex_unlock(&chip->io_lock); return ret; } =20 @@ -136,6 +138,7 @@ static ssize_t ad7816_store_mode(struct device *dev, struct iio_dev *indio_dev =3D dev_to_iio_dev(dev); struct ad7816_chip_info *chip =3D iio_priv(indio_dev); =20 + mutex_lock(&chip->io_lock); if (strcmp(buf, "full") =3D=3D 0) { gpiod_set_value(chip->rdwr_pin, 1); chip->mode =3D AD7816_FULL; @@ -143,6 +146,7 @@ static ssize_t ad7816_store_mode(struct device *dev, gpiod_set_value(chip->rdwr_pin, 0); chip->mode =3D AD7816_PD; } + mutex_unlock(&chip->io_lock); =20 return len; } @@ -200,7 +204,9 @@ static ssize_t ad7816_store_channel(struct device *dev, return -EINVAL; } =20 + mutex_lock(&chip->io_lock); chip->channel_id =3D data; + mutex_unlock(&chip->io_lock); =20 return len; } @@ -322,7 +328,9 @@ static inline ssize_t ad7816_set_oti(struct device *dev, if (ret) return -EIO; =20 + mutex_lock(&chip->io_lock); chip->oti_data[chip->channel_id] =3D data; + mutex_unlock(&chip->io_lock); =20 return len; } @@ -363,6 +371,7 @@ static int ad7816_probe(struct spi_device *spi_dev) dev_set_drvdata(&spi_dev->dev, indio_dev); =20 chip->spi_dev =3D spi_dev; + mutex_init(&chip->io_lock); for (i =3D 0; i <=3D AD7816_CS_MAX; i++) chip->oti_data[i] =3D 203; =20 --=20 2.43.0