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[90.182.112.124]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49807b917efsm367415595e9.11.2026.08.03.06.49.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Aug 2026 06:49:37 -0700 (PDT) Date: Mon, 3 Aug 2026 15:49:35 +0200 From: Joshua Crofts To: Abdelnasser Hussein Cc: jic23@kernel.org, nuno.sa@analog.com, Michael.Hennerich@analog.com, gregkh@linuxfoundation.org, linux-iio@vger.kernel.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/2] staging: iio: ad7816: serialize ad7816_spi_read() with a mutex Message-ID: <20260803154935.000014b5@gmail.com> In-Reply-To: <20260803121520.6274-2-abdelnasserhussein11@gmail.com> References: <0bde2343-8a70-44d4-9b27-8ce42c099309@baylibre.com> <20260803121520.6274-1-abdelnasserhussein11@gmail.com> <20260803121520.6274-2-abdelnasserhussein11@gmail.com> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.51; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 3 Aug 2026 15:15:19 +0300 Abdelnasser Hussein wrote: > The ad7816_spi_read() path performs a sequence of SPI transfers and GPIO > state changes that must not be interleaved with another read operation. > > Without serialization, concurrent callers can interfere with each other, > leading to inconsistent device state and incorrect data being returned. > > Add a mutex to struct ad7816_chip_info and hold it across the entire read > sequence to ensure exclusive access to the device. > > Signed-off-by: Abdelnasser Hussein > --- > drivers/staging/iio/adc/ad7816.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/staging/iio/adc/ad7816.c b/drivers/staging/iio/adc/ad7816.c > index 0e32a2295990..b5a0c2871e00 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 lock; /* protect device state during SPI transfers */ > }; > > enum ad7816_type { > @@ -67,11 +68,14 @@ static int ad7816_spi_read(struct ad7816_chip_info *chip, u16 *data) > int ret; > __be16 buf; > > + mutex_lock(&chip->lock); This patch would benefit from using guard(mutex) from the header. > + > gpiod_set_value(chip->rdwr_pin, 1); > gpiod_set_value(chip->rdwr_pin, 0); > ret = spi_write(spi_dev, &chip->channel_id, sizeof(chip->channel_id)); > if (ret < 0) { > dev_err(&spi_dev->dev, "SPI channel setting error\n"); > + mutex_unlock(&chip->lock); > return ret; > } > gpiod_set_value(chip->rdwr_pin, 1); > @@ -94,11 +98,13 @@ static int ad7816_spi_read(struct ad7816_chip_info *chip, u16 *data) > ret = spi_read(spi_dev, &buf, sizeof(*data)); > if (ret < 0) { > dev_err(&spi_dev->dev, "SPI data read error\n"); > + mutex_unlock(&chip->lock); > + > return ret; > } > > *data = be16_to_cpu(buf); > - > + mutex_unlock(&chip->lock); > return ret; > } > > @@ -359,7 +365,7 @@ static int ad7816_probe(struct spi_device *spi_dev) > if (!indio_dev) > return -ENOMEM; > chip = iio_priv(indio_dev); > - > + mutex_init(&chip->lock); devm_mutex_init() since the driver uses managed resources. Additionally, please check the return value of the function and just return on failure. > chip->spi_dev = spi_dev; > for (i = 0; i <= AD7816_CS_MAX; i++) > chip->oti_data[i] = 203; -- Kind regards, Joshua Crofts