[PATCH v2] i2c: add pmic_reg_read() for PBL use

[Bastian Krause <bst@xxxxxxxxxxxxxx>]

Add a common PMIC read function to PBL which allows easy porting of
U-Boot's pmic_reg_read() in lowlevel board code.

Signed-off-by: Bastian Krause <bst@xxxxxxxxxxxxxx>
---
Changes since (implicit) v1:
- make function static inline as suggested by Ahmad
- change void *buf to u32 *val to resemble's U-Boot's pmic_reg_read() as
  suggested by Ahmad
---
 include/pbl/pmic.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/include/pbl/pmic.h b/include/pbl/pmic.h
index 0f882c5649d..4eeee31d46c 100644
--- a/include/pbl/pmic.h
+++ b/include/pbl/pmic.h
@@ -9,6 +9,30 @@ struct pmic_config {
 	u8 val;
 };
 
+static inline void pmic_reg_read(struct pbl_i2c *i2c, int addr, u8 reg, u32 *val)
+{
+	int ret;
+	u8 buf[1];
+	struct i2c_msg msg[] = {
+		{
+			.addr = addr,
+			.buf = &reg,
+			.len = 1,
+		}, {
+			.addr = addr,
+			.flags = I2C_M_RD,
+			.buf = buf,
+			.len = 1,
+		},
+	};
+
+	ret = pbl_i2c_xfer(i2c, msg, ARRAY_SIZE(msg));
+	if (ret != ARRAY_SIZE(msg))
+		pr_err("Failed to read from pmic@%x: %d\n", addr, ret);
+
+	*val = buf[0];
+}
+
 static void pmic_reg_write(struct pbl_i2c *i2c, int addr, u8 reg, u8 val)
 {
 	int ret;
-- 
2.39.2