nvmem: import Linux nvmem_cell_read_variable_le_u32

We already have nvmem_cell_get_and_read(), so add its Linux sibling
nvmem_cell_read_variable_le_u32 as well, which additionally takes care
of conversion to little-endian.

Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Link: https://lore.barebox.org/20220818051955.2088238-7-a.fatoum@pengutronix.de
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

1 files changed, 33 insertions, 0 deletions

diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
index fed387c43a..c5fe5f6b76 100644
--- a/drivers/nvmem/core.c
+++ b/drivers/nvmem/core.c
@@ -803,3 +803,36 @@ void *nvmem_cell_get_and_read(struct device_node *np, const char *cell_name,
 	return value;
 }
 EXPORT_SYMBOL_GPL(nvmem_cell_get_and_read);
+
+/**
+ * nvmem_cell_read_variable_le_u32() - Read up to 32-bits of data as a little endian number.
+ *
+ * @dev: Device that requests the nvmem cell.
+ * @cell_id: Name of nvmem cell to read.
+ * @val: pointer to output value.
+ *
+ * Return: 0 on success or negative errno.
+ */
+int nvmem_cell_read_variable_le_u32(struct device_d *dev, const char *cell_id,
+				    u32 *val)
+{
+	size_t len;
+	const u8 *buf;
+	int i;
+
+	len = sizeof(*val);
+
+	buf = nvmem_cell_get_and_read(dev->device_node, cell_id, len);
+	if (IS_ERR(buf))
+		return PTR_ERR(buf);
+
+	/* Copy w/ implicit endian conversion */
+	*val = 0;
+	for (i = 0; i < len; i++)
+		*val |= buf[i] << (8 * i);
+
+	kfree(buf);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(nvmem_cell_read_variable_le_u32);