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Tue, 15 Sep 2026 01:00:29 -0700 (PDT) From: Abdelnasser Hussein To: jic23@kernel.org, gregkh@linuxfoundation.org, nuno.sa@analog.com, Michael.Hennerich@analog.com Cc: dlechner@baylibre.com, andy@kernel.org, linux@analog.com, linux-iio@vger.kernel.org, linux-staging@lists.linux.dev, linux-kernel@vger.kernel.org, joshua.crofts1@gmail.com, Abdelnasser Hussein Subject: [PATCH v7 3/3] staging: iio: adc: ad7816: Fix DMA safety issues in SPI transfers Date: Tue, 15 Sep 2026 10:59:39 +0300 Message-ID: <20260915075939.18180-4-abdelnasserhussein11@gmail.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260915075939.18180-1-abdelnasserhussein11@gmail.com> References: <20260915075939.18180-1-abdelnasserhussein11@gmail.com> Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The SPI operations in this driver are not DMA safe: 1. spi_read() uses a stack-allocated buffer. 2. spi_write() in ad7816_spi_read() uses a struct member that shares a cacheline with other variables. 3. spi_write() in ad7816_spi_write() passes a stack parameter by reference. Fix these violations by replacing all spi_read() and spi_write() calls with spi_write_then_read(). This safely handles DMA by internally allocating a bounce buffer for the transfers, avoiding cacheline sharing issues without needing dedicated aligned buffers. This implicitly corrects the size argument in read to sizeof(buf). Fixes: 7024425db64a ("staging: iio: adc: new driver for AD7816 devices") Signed-off-by: Abdelnasser Hussein --- drivers/staging/iio/adc/ad7816.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/staging/iio/adc/ad7816.c b/drivers/staging/iio/adc/ad7816.c index c18093ca8a82..f76f0215119a 100644 --- a/drivers/staging/iio/adc/ad7816.c +++ b/drivers/staging/iio/adc/ad7816.c @@ -74,7 +74,7 @@ static int ad7816_spi_read(struct ad7816_chip_info *chip, u16 *data) 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)); + ret = spi_write_then_read(spi_dev, &chip->channel_id, sizeof(chip->channel_id), NULL, 0); if (ret < 0) { dev_err(&spi_dev->dev, "SPI channel setting error\n"); return ret; @@ -96,7 +96,7 @@ static int ad7816_spi_read(struct ad7816_chip_info *chip, u16 *data) gpiod_set_value(chip->rdwr_pin, 0); gpiod_set_value(chip->rdwr_pin, 1); - ret = spi_read(spi_dev, &buf, sizeof(*data)); + ret = spi_write_then_read(spi_dev, NULL, 0, &buf, sizeof(buf)); if (ret < 0) { dev_err(&spi_dev->dev, "SPI data read error\n"); return ret; @@ -116,7 +116,7 @@ static int ad7816_spi_write(struct ad7816_chip_info *chip, u8 data) gpiod_set_value(chip->rdwr_pin, 1); gpiod_set_value(chip->rdwr_pin, 0); - ret = spi_write(spi_dev, &data, sizeof(data)); + ret = spi_write_then_read(spi_dev, &data, sizeof(data), NULL, 0); if (ret < 0) dev_err(&spi_dev->dev, "SPI oti data write error\n"); -- 2.54.0