From 63f72f0cd0d01ef6138bfba80b7cd19d57c6602c Mon Sep 17 00:00:00 2001
From: Werner Zeh <werner.zeh@siemens.com>
Date: Fri, 26 Aug 2022 13:17:52 +0200
Subject: [PATCH] device/i2c_bus: Add routines to read and write multiple bytes

Some devices require that several bytes are written with a single I2C
write command. Extend the i2c_bus interface functions and add both, read
and write for more than one byte at a defined byte offset.

Change-Id: I0eec2e1d4185170f02b4ab35aa6546dc69569303
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/67098
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Mario Scheithauer <mario.scheithauer@siemens.com>
---
 src/device/i2c_bus.c         | 70 ++++++++++++++++++++++++++++++++++++
 src/include/device/i2c_bus.h | 14 ++++++++
 2 files changed, 84 insertions(+)

diff --git a/src/device/i2c_bus.c b/src/device/i2c_bus.c
index 8368c247b8..f0d7dd116e 100644
--- a/src/device/i2c_bus.c
+++ b/src/device/i2c_bus.c
@@ -183,3 +183,73 @@ int i2c_dev_read_at16(struct device *const dev, uint8_t *const buf, const size_t
 		return -1;
 	}
 }
+
+int i2c_dev_read_at(struct device *const dev, uint8_t *const buf, const size_t len,
+		      uint8_t off)
+{
+	struct device *const busdev = i2c_busdev(dev);
+	if (!busdev)
+		return -1;
+
+	if (busdev->ops->ops_i2c_bus) {
+		const struct i2c_msg msg[] = {
+			{
+				.flags	= 0,
+				.slave	= dev->path.i2c.device,
+				.buf	= &off,
+				.len	= sizeof(off),
+			},
+			{
+				.flags	= I2C_M_RD,
+				.slave	= dev->path.i2c.device,
+				.buf	= buf,
+				.len	= len,
+			},
+		};
+
+		const int ret = busdev->ops->ops_i2c_bus->transfer(busdev, msg,
+								   ARRAY_SIZE(msg));
+		if (ret)
+			return ret;
+		else
+			return len;
+	} else {
+		printk(BIOS_ERR, "%s Missing ops_i2c_bus->transfer", dev_path(busdev));
+		return -1;
+	}
+}
+
+int i2c_dev_write_at(struct device *const dev, uint8_t *const buf, const size_t len,
+		       uint8_t off)
+{
+	struct device *const busdev = i2c_busdev(dev);
+	if (!busdev)
+		return -1;
+
+	if (busdev->ops->ops_i2c_bus) {
+		const struct i2c_msg msg[] = {
+			{
+				.flags	= 0,
+				.slave	= dev->path.i2c.device,
+				.buf	= &off,
+				.len	= sizeof(off),
+			},
+			{
+				.flags	= I2C_M_NOSTART,
+				.slave	= dev->path.i2c.device,
+				.buf	= buf,
+				.len	= len,
+			},
+		};
+
+		const int ret = busdev->ops->ops_i2c_bus->transfer(busdev, msg,
+								   ARRAY_SIZE(msg));
+		if (ret)
+			return ret;
+		else
+			return len;
+	} else {
+		printk(BIOS_ERR, "%s Missing ops_i2c_bus->transfer", dev_path(busdev));
+		return -1;
+	}
+}
diff --git a/src/include/device/i2c_bus.h b/src/include/device/i2c_bus.h
index 1a7e777278..4c9b98d14f 100644
--- a/src/include/device/i2c_bus.h
+++ b/src/include/device/i2c_bus.h
@@ -90,5 +90,19 @@ int i2c_dev_writeb_at(struct device *, uint8_t off, uint8_t val);
  * value on error.
  */
 int i2c_dev_read_at16(struct device *, uint8_t *buf, size_t len, uint16_t off);
+/*
+ * Sends the 8-bit register offset `off` and reads `len` bytes into `buf`.
+ *
+ * Returns the number of bytes read on success, negative `enum cb_err`
+ * value on error.
+ */
+int i2c_dev_read_at(struct device *, uint8_t *buf, size_t len, uint8_t off);
+/*
+ * Sends the 8-bit register offset `off` and writes `len` bytes from `buf`.
+ *
+ * Returns the number of bytes written on success, negative `enum cb_err`
+ * value on error.
+ */
+int i2c_dev_write_at(struct device *, uint8_t *buf, size_t len, uint8_t off);
 
 #endif	/* _DEVICE_I2C_BUS_H_ */