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From: Jonathan Cameron <jic23@kernel.org>
To: linux-iio@vger.kernel.org,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	Nuno Sa <Nuno.Sa@analog.com>
Cc: "Linus Walleij" <linus.walleij@linaro.org>,
	"Jan Kiszka" <jan.kiszka@siemens.com>,
	"Jonathan Cameron" <Jonathan.Cameron@huawei.com>,
	"Nuno Sá" <nuno.sa@analog.com>
Subject: [PATCH v2 4/4] iio: imu: adis16400: Fix buffer alignment requirements.
Date: Sun, 13 Jun 2021 16:10:39 +0100	[thread overview]
Message-ID: <20210613151039.569883-5-jic23@kernel.org> (raw)
In-Reply-To: <20210613151039.569883-1-jic23@kernel.org>

From: Jonathan Cameron <Jonathan.Cameron@huawei.com>

iio_push_to_buffers_with_timestamp() requires that the buffer
is 8 byte alignment to ensure an inserted timestamp is naturally aligned.

This requirement was not met here when burst mode is in use beause
of a leading u16. Use the new iio_push_to_buffers_with_ts_unaligned()
function that has more relaxed requirements.

It is somewhat complex to access that actual data length, but a
safe bound can be found by using scan_bytes - sizeof(timestamp) so that
is used in this path.

More efficient approaches exist, but this ensure correctness at the
cost of using a bounce buffer.

Fixes: 5075e0720d93 ("iio: imu: adis: generalize burst mode support")
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
---
 drivers/iio/imu/adis16400.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/iio/imu/adis16400.c b/drivers/iio/imu/adis16400.c
index cb8d3ffab6fc..66a83ebd3109 100644
--- a/drivers/iio/imu/adis16400.c
+++ b/drivers/iio/imu/adis16400.c
@@ -648,13 +648,23 @@ static irqreturn_t adis16400_trigger_handler(int irq, void *p)
 	if (ret)
 		dev_err(&adis->spi->dev, "Failed to read data: %d\n", ret);
 
-	if (st->variant->flags & ADIS16400_BURST_DIAG_STAT)
+	if (st->variant->flags & ADIS16400_BURST_DIAG_STAT) {
 		buffer = adis->buffer + sizeof(u16);
-	else
-		buffer = adis->buffer;
+		/*
+		 * The size here is always larger than, or equal to the true
+		 * size of the channel data. This may result in a larger copy
+		 * than necessary, but as the target buffer will be
+		 * buffer->scan_bytes this will be safe.
+		 */
+		iio_push_to_buffers_with_ts_unaligned(indio_dev, buffer,
+						      indio_dev->scan_bytes - sizeof(pf->timestamp),
+						      pf->timestamp);
+	} else {
+		iio_push_to_buffers_with_timestamp(indio_dev,
+						   adis->buffer,
+						   pf->timestamp);
+	}
 
-	iio_push_to_buffers_with_timestamp(indio_dev, buffer,
-		pf->timestamp);
 
 	iio_trigger_notify_done(indio_dev->trig);
 
-- 
2.32.0


  parent reply	other threads:[~2021-06-13 15:08 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-13 15:10 [PATCH v2 0/4] IIO: Alignment fixes part 4 - bounce buffers for the hard cases Jonathan Cameron
2021-06-13 15:10 ` [PATCH v2 1/4] iio: core: Introduce iio_push_to_buffers_with_ts_unaligned() Jonathan Cameron
2021-06-14  8:33   ` Sa, Nuno
2021-06-13 15:10 ` [PATCH v2 2/4] iio: adc: ti-adc108s102: Fix alignment of buffer pushed to iio buffers Jonathan Cameron
2021-06-13 15:10 ` [PATCH v2 3/4] iio: gyro: mpu3050: Fix alignment and size issues with buffers Jonathan Cameron
2021-06-13 15:10 ` Jonathan Cameron [this message]
2021-06-14  8:25   ` [PATCH v2 4/4] iio: imu: adis16400: Fix buffer alignment requirements Sa, Nuno
2021-07-18 14:55 ` [PATCH v2 0/4] IIO: Alignment fixes part 4 - bounce buffers for the hard cases Jonathan Cameron
2021-10-03 15:54   ` Jonathan Cameron

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