[PATCH v2] nvmem: rmem: Fix return value of rmem_read()

[Joy Chakraborty <joychakr@google.com>]

reg_read() callback registered with nvmem core expects an integer error
as a return value but rmem_read() returns the number of bytes read, as a
result error checks in nvmem core fail even when they shouldn't.

Return 0 on success where number of bytes read match the number of bytes
requested and a negative error -EINVAL on all other cases.

Fixes: 5a3fa75a4d9c ("nvmem: Add driver to expose reserved memory as nvmem")
Cc: stable@vger.kernel.org
Signed-off-by: Joy Chakraborty <joychakr@google.com>
---
 drivers/nvmem/rmem.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/nvmem/rmem.c b/drivers/nvmem/rmem.c
index 752d0bf4445e..a74dfa279ff4 100644
--- a/drivers/nvmem/rmem.c
+++ b/drivers/nvmem/rmem.c
@@ -46,7 +46,12 @@ static int rmem_read(void *context, unsigned int offset,
 
 	memunmap(addr);
 
-	return count;
+	if (count != bytes) {
+		dev_err(priv->dev, "Failed read memory (%d)\n", count);
+		return -EINVAL;
+	}
+
+	return 0;
 }
 
 static int rmem_probe(struct platform_device *pdev)
-- 
2.43.0.594.gd9cf4e227d-goog