[PATCH v2] nvmem: meson-mx-efuse: allow reading data smaller than word_size

Martin Blumenstingl martin.blumenstingl at googlemail.com
Sat Jul 27 12:34:14 PDT 2019

Some Amlogic boards store the Ethernet MAC address inside the eFuse. The
Ethernet MAC address uses 6 bytes. The existing logic in
meson_mx_efuse_read() would write beyond the end of the data buffer when
trying to read data with a size that is not aligned to word_size (4
bytes on Meson8, Meson8b and Meson8m2).

Calculate the remaining data to copy inside meson_mx_efuse_read() so
reading 6 bytes doesn't write beyond the end of the data buffer.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl at googlemail.com>
Changes since v1:
- switch from min() to min_t() to get rid of a compiler warning

 drivers/nvmem/meson-mx-efuse.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/nvmem/meson-mx-efuse.c b/drivers/nvmem/meson-mx-efuse.c
index 2976aef87c82..e8fc0baa09e7 100644
--- a/drivers/nvmem/meson-mx-efuse.c
+++ b/drivers/nvmem/meson-mx-efuse.c
@@ -155,7 +155,8 @@ static int meson_mx_efuse_read(void *context, unsigned int offset,
 		if (err)
-		memcpy(buf + i, &tmp, efuse->config.word_size);
+		memcpy(buf + i, &tmp,
+		       min_t(size_t, bytes - i, efuse->config.word_size));
 	meson_mx_efuse_mask_bits(efuse, MESON_MX_EFUSE_CNTL1,

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