linux-kernel - [PATCH 08/14] iio: pressure: mprls0025pa: stricter checks for the status byte

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Message-Id: <20251218-mprls_cleanup-v1-8-b36a170f1a5c@subdimension.ro>
Date: Thu, 18 Dec 2025 13:05:50 +0200
From: Petre Rodan <petre.rodan@...dimension.ro>
To: Jonathan Cameron <jic23@...nel.org>, 
 David Lechner <dlechner@...libre.com>, 
 Nuno Sá <nuno.sa@...log.com>, 
 Andy Shevchenko <andy@...nel.org>, Andreas Klinger <ak@...klinger.de>
Cc: linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [PATCH 08/14] iio: pressure: mprls0025pa: stricter checks for the
 status byte

Make sure a valid conversion comes with a status byte that only has
the MPR_ST_POWER bit set.
Return -EBUSY if also MPR_ST_BUSY is set or -EIO otherwise.

Signed-off-by: Petre Rodan <petre.rodan@...dimension.ro>
---
 drivers/iio/pressure/mprls0025pa.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/pressure/mprls0025pa.c b/drivers/iio/pressure/mprls0025pa.c
index 7f8dc47d7073..973d205da3e9 100644
--- a/drivers/iio/pressure/mprls0025pa.c
+++ b/drivers/iio/pressure/mprls0025pa.c
@@ -12,6 +12,7 @@
 #include <linux/array_size.h>
 #include <linux/bitfield.h>
 #include <linux/bits.h>
+#include <linux/errno.h>
 #include <linux/math64.h>
 #include <linux/mod_devicetable.h>
 #include <linux/module.h>
@@ -195,9 +196,10 @@ static void mpr_reset(struct mpr_data *data)
  * waits for a maximum of one second for the interrupt.
  *
  * Return:
- * * 0		- OK, the pressure value could be read
- * * -ETIMEDOUT	- Timeout while waiting for the EOC interrupt or busy flag is
- *		  still set after nloops attempts of reading
+ * * 0          - OK, the pressure value could be read
+ * * -EBUSY     - Sensor does not have a new conversion ready
+ * * -ETIMEDOUT - Timeout while waiting for the EOC interrupt
+ * * -EIO       - Invalid status byte received from sensor
  */
 static int mpr_read_pressure(struct mpr_data *data, s32 *press)
 {
@@ -250,10 +252,25 @@ static int mpr_read_pressure(struct mpr_data *data, s32 *press)
 	if (ret < 0)
 		return ret;
 
-	if (data->rx_buf[0] & MPR_ST_ERR_FLAG) {
+	/*
+	 * Status byte flags
+	 *  bit7 SANITY_CHK   - must always be 0
+	 *  bit6 MPR_ST_POWER - 1 if device is powered
+	 *  bit5 MPR_ST_BUSY  - 1 if device has no new conversion ready
+	 *  bit4 SANITY_CHK   - must always be 0
+	 *  bit3 SANITY_CHK   - must always be 0
+	 *  bit2 MEMORY_ERR   - 1 if integrity test has failed
+	 *  bit1 SANITY_CHK   - must always be 0
+	 *  bit0 MATH_ERR     - 1 during internal math saturation error
+	 */
+
+	if (data->rx_buf[0] == (MPR_ST_POWER | MPR_ST_BUSY))
+		return -EBUSY;
+
+	if (data->rx_buf[0] != MPR_ST_POWER) {
 		dev_err(data->dev,
-			"unexpected status byte %02x\n", data->rx_buf[0]);
-		return -ETIMEDOUT;
+			"unexpected status byte 0x%02x\n", data->rx_buf[0]);
+		return -EIO;
 	}
 
 	*press = get_unaligned_be24(&data->rx_buf[1]);

-- 
2.51.2