ACPM PMIC command handlers returned a u8 value when they should
have returned either zero or negative error codes.
Translate the APM PMIC errno to linux errno.

Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/linux-input/aElHlTApXj-W_o1r@stanley.mountain/
Fixes: a88927b534ba ("firmware: add Exynos ACPM protocol driver")
Cc: stable@vger.kernel.org
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
---
Changes in v2:
- remove `enum acpm_pmic_error_codes`. use designated initializers in
  the array instead.
- constify acpm_pmic_linux_errmap
- drop inline from acpm_pmic_to_linux_errno
- s/errno/err
- Link to v1: https://lore.kernel.org/r/20250821-acpm-pmix-fix-errno-v1-1-771a5969324c@linaro.org
---
 drivers/firmware/samsung/exynos-acpm-pmic.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/firmware/samsung/exynos-acpm-pmic.c b/drivers/firmware/samsung/exynos-acpm-pmic.c
index 39b33a356ebd240506b6390163229a70a2d1fe68..961d7599e4224ef6ebe64dfa2fcb441a4dbd78a3 100644
--- a/drivers/firmware/samsung/exynos-acpm-pmic.c
+++ b/drivers/firmware/samsung/exynos-acpm-pmic.c
@@ -4,7 +4,9 @@
  * Copyright 2020 Google LLC.
  * Copyright 2024 Linaro Ltd.
  */
+#include <linux/array_size.h>
 #include <linux/bitfield.h>
+#include <linux/errno.h>
 #include <linux/firmware/samsung/exynos-acpm-protocol.h>
 #include <linux/ktime.h>
 #include <linux/types.h>
@@ -33,6 +35,19 @@ enum exynos_acpm_pmic_func {
 	ACPM_PMIC_BULK_WRITE,
 };
 
+static const int acpm_pmic_linux_errmap[] = {
+	[0] = 0, /* ACPM_PMIC_SUCCESS */
+	[1] = -EACCES, /* Read register can't be accessed or issues to access it. */
+	[2] = -EACCES, /* Write register can't be accessed or issues to access it. */
+};
+
+static int acpm_pmic_to_linux_err(int err)
+{
+	if (err >= 0 && err < ARRAY_SIZE(acpm_pmic_linux_errmap))
+		return acpm_pmic_linux_errmap[err];
+	return -EIO;
+}
+
 static inline u32 acpm_pmic_set_bulk(u32 data, unsigned int i)
 {
 	return (data & ACPM_PMIC_BULK_MASK) << (ACPM_PMIC_BULK_SHIFT * i);
@@ -79,7 +94,7 @@ int acpm_pmic_read_reg(const struct acpm_handle *handle,
 
 	*buf = FIELD_GET(ACPM_PMIC_VALUE, xfer.rxd[1]);
 
-	return FIELD_GET(ACPM_PMIC_RETURN, xfer.rxd[1]);
+	return acpm_pmic_to_linux_err(FIELD_GET(ACPM_PMIC_RETURN, xfer.rxd[1]));
 }
 
 static void acpm_pmic_init_bulk_read_cmd(u32 cmd[4], u8 type, u8 reg, u8 chan,
@@ -110,7 +125,7 @@ int acpm_pmic_bulk_read(const struct acpm_handle *handle,
 	if (ret)
 		return ret;
 
-	ret = FIELD_GET(ACPM_PMIC_RETURN, xfer.rxd[1]);
+	ret = acpm_pmic_to_linux_err(FIELD_GET(ACPM_PMIC_RETURN, xfer.rxd[1]));
 	if (ret)
 		return ret;
 
@@ -150,7 +165,7 @@ int acpm_pmic_write_reg(const struct acpm_handle *handle,
 	if (ret)
 		return ret;
 
-	return FIELD_GET(ACPM_PMIC_RETURN, xfer.rxd[1]);
+	return acpm_pmic_to_linux_err(FIELD_GET(ACPM_PMIC_RETURN, xfer.rxd[1]));
 }
 
 static void acpm_pmic_init_bulk_write_cmd(u32 cmd[4], u8 type, u8 reg, u8 chan,
@@ -190,7 +205,7 @@ int acpm_pmic_bulk_write(const struct acpm_handle *handle,
 	if (ret)
 		return ret;
 
-	return FIELD_GET(ACPM_PMIC_RETURN, xfer.rxd[1]);
+	return acpm_pmic_to_linux_err(FIELD_GET(ACPM_PMIC_RETURN, xfer.rxd[1]));
 }
 
 static void acpm_pmic_init_update_cmd(u32 cmd[4], u8 type, u8 reg, u8 chan,
@@ -220,5 +235,5 @@ int acpm_pmic_update_reg(const struct acpm_handle *handle,
 	if (ret)
 		return ret;
 
-	return FIELD_GET(ACPM_PMIC_RETURN, xfer.rxd[1]);
+	return acpm_pmic_to_linux_err(FIELD_GET(ACPM_PMIC_RETURN, xfer.rxd[1]));
 }

---
base-commit: c17b750b3ad9f45f2b6f7e6f7f4679844244f0b9
change-id: 20250820-acpm-pmix-fix-errno-92b3e6e17d1b

Best regards,
-- 
Tudor Ambarus <tudor.ambarus@linaro.org>