[coreboot-gerrit] Change in coreboot[master]: device/i2c_bus: Add i2c_dev_writeb_at16()

[shkim (Code Review)]

Hello SH Kim,

I'd like you to do a code review. Please visit

https://review.coreboot.org/c/coreboot/+/46290

to review the following change.

Change subject: device/i2c_bus: Add i2c_dev_writeb_at16()
......................................................................

device/i2c_bus: Add i2c_dev_writeb_at16()

i2c_dev_writeb_at16() sends a 16-bit offset to the I2C chip (for larger
EEPROM parts), then write a byte.

Change-Id: Ic8ee87fd2175d7c2d4359ece425519aa25df9a16
Signed-off-by: Seunghwan Kim 
---
M src/device/i2c_bus.c
M src/include/device/i2c_bus.h
2 files changed, 35 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/90/46290/1

diff --git a/src/device/i2c_bus.c b/src/device/i2c_bus.c
index a65cdad..bbe1094 100644
--- a/src/device/i2c_bus.c
+++ b/src/device/i2c_bus.c
@@ -184,3 +184,32 @@
    	return -1;
    }
 }
+
+int i2c_dev_writeb_at16(struct device *const dev,
+			const uint16_t off, const uint8_t val)
+{
+	struct device *const busdev = i2c_busdev(dev);
+	if (!busdev)
+		return -1;
+
+	if (busdev->ops->ops_i2c_bus) {
+		uint8_t buf[3];
+		const struct i2c_msg msg = {
+			.flags	= 0,
+			.slave	= dev->path.i2c.device,
+			.buf	= buf,
+			.len	= sizeof(buf),
+		};
+
+		write_be16((uint16_t *)buf, off);
+		buf[2] = val;
+
+		return busdev->ops->ops_i2c_bus->transfer(busdev, &msg, 1);
+	} else if (busdev->ops->ops_smbus_bus->write_byte) {
+		return busdev->ops->ops_smbus_bus->write_byte(dev, off, val);
+	} else {
+		printk(BIOS_ERR, "%s Missing ops_smbus_bus->write_byte",
+		       dev_path(busdev));
+		return -1;
+	}
+}
diff --git a/src/include/device/i2c_bus.h b/src/include/device/i2c_bus.h
index b5e7710..6028e41 100644
--- a/src/include/device/i2c_bus.h
+++ b/src/include/device/i2c_bus.h
@@ -86,4 +86,10 @@
  */
 int i2c_dev_read_at16(struct device *, uint8_t *buf, size_t len, uint16_t off);

+/*
+ * Sends the 16-bit register offset `off` followed by the byte `val`.
+ *
+ * Returns 0 on success, negative `enum cb_err` value on error.
+ */
+int i2c_dev_writeb_at16(struct device *, uint16_t off, uint8_t val);
 #endif	/* _DEVICE_I2C_BUS_H_ */