[PATCH v2 4/6] iio: adis: Add burst_max_len variable

["Nuno Sá" <nuno.sa@analog.com>]

Add burst_max_len to `adis_burst`. This is useful for devices which
support different burst modes with different sizes. The buffer to be
used in the spi transfer is allocated with this variable making sure
that has space for all burst modes. The spi transfer length should hold
the "real" burst length depending on the current burst mode configured
in the device.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
---
 drivers/iio/imu/adis_buffer.c | 11 ++++++++---
 include/linux/iio/imu/adis.h  |  3 +++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/imu/adis_buffer.c b/drivers/iio/imu/adis_buffer.c
index 7871b468e9e9..ddf4bdca7e72 100644
--- a/drivers/iio/imu/adis_buffer.c
+++ b/drivers/iio/imu/adis_buffer.c
@@ -23,25 +23,30 @@ static int adis_update_scan_mode_burst(struct iio_dev *indio_dev,
 	const unsigned long *scan_mask)
 {
 	struct adis *adis = iio_device_get_drvdata(indio_dev);
-	unsigned int burst_length;
+	unsigned int burst_length, burst_max_length;
 	u8 *tx;
 
 	/* All but the timestamp channel */
 	burst_length = (indio_dev->num_channels - 1) * sizeof(u16);
 	burst_length += adis->burst->extra_len;
 
+	if (adis->burst->burst_max_len)
+		burst_max_length = adis->burst->burst_max_len;
+	else
+		burst_max_length = burst_length;
+
 	adis->xfer = kcalloc(2, sizeof(*adis->xfer), GFP_KERNEL);
 	if (!adis->xfer)
 		return -ENOMEM;
 
-	adis->buffer = kzalloc(burst_length + sizeof(u16), GFP_KERNEL);
+	adis->buffer = kzalloc(burst_max_length + sizeof(u16), GFP_KERNEL);
 	if (!adis->buffer) {
 		kfree(adis->xfer);
 		adis->xfer = NULL;
 		return -ENOMEM;
 	}
 
-	tx = adis->buffer + burst_length;
+	tx = adis->buffer + burst_max_length;
 	tx[0] = ADIS_READ_REG(adis->burst->reg_cmd);
 	tx[1] = 0;
 
diff --git a/include/linux/iio/imu/adis.h b/include/linux/iio/imu/adis.h
index 94031b3fc9d5..5bdd6f457e78 100644
--- a/include/linux/iio/imu/adis.h
+++ b/include/linux/iio/imu/adis.h
@@ -502,11 +502,14 @@ int adis_single_conversion(struct iio_dev *indio_dev,
  * @en			burst mode enabled
  * @reg_cmd		register command that triggers burst
  * @extra_len		extra length to account in the SPI RX buffer
+ * @burst_max_len	holds the maximum burst size when the device supports
+ *			more than one burst mode with different sizes
  */
 struct adis_burst {
 	bool		en;
 	unsigned int	reg_cmd;
 	unsigned int	extra_len;
+	const u32	burst_max_len;
 };
 
 int
-- 
2.25.1