linux-kernel - [PATCH 1/4] nvmem: core: Read into buffers larger than data

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Date: Tue,  6 Feb 2024 15:37:08 +0100
From: Markus Schneider-Pargmann <msp@...libre.com>
To: Nishanth Menon <nm@...com>,
	Vignesh Raghavendra <vigneshr@...com>,
	Tero Kristo <kristo@...nel.org>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Santosh Shilimkar <ssantosh@...nel.org>
Cc: Andrew Davis <afd@...com>,
	linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Markus Schneider-Pargmann <msp@...libre.com>
Subject: [PATCH 1/4] nvmem: core: Read into buffers larger than data

The actual size that nvmem is using internally on a specific platform
with a specific devicetree may not be known in the consumer code. The
maximum size may be available at the same time.

Allow the use of larger buffers in nvmem_cell_read_common() by setting
buffers that are too large to zero before copying into them.

Signed-off-by: Markus Schneider-Pargmann <msp@...libre.com>
---
 drivers/nvmem/core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index 980123fb4dde..6fa061ede605 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -1806,12 +1806,14 @@ static int nvmem_cell_read_common(struct device *dev, const char *cell_id,
 		nvmem_cell_put(cell);
 		return PTR_ERR(buf);
 	}
-	if (len != count) {
+	if (len > count) {
 		kfree(buf);
 		nvmem_cell_put(cell);
 		return -EINVAL;
+	} else if (len < count) {
+		memset(val + len, 0, count - len);
 	}
-	memcpy(val, buf, count);
+	memcpy(val, buf, len);
 	kfree(buf);
 	nvmem_cell_put(cell);
 
-- 
2.43.0