i2c master: Add block read/write commands.

These commands are used by several modules that manage their own block
read/write protocols today.  This is the first of a series that
refactors several modules to use the I2C driver functions instead of
their own.

BUG=chromium:871851
BRANCH=none
TEST=make -j buildall; USB-PD and motionsense testing on Grunt
convertible, which exercises several users of the new interface.
Signed-off-by: Jonathan Brandmeyer <jbrandmeyer@chromium.org>

Change-Id: I08475a72031e5fbf49dc344d5b4858622f0d5e93
Reviewed-on: https://chromium-review.googlesource.com/1167957
Commit-Ready: Jonathan Brandmeyer <jbrandmeyer@chromium.org>
Tested-by: Jonathan Brandmeyer <jbrandmeyer@chromium.org>
Reviewed-by: Jett Rink <jettrink@chromium.org>
(cherry picked from commit 21e235dbe468bfa80bab86900ab4baeb48533a94)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2607209
Tested-by: David Huang <david.huang@quanta.corp-partner.google.com>
Auto-Submit: David Huang <david.huang@quanta.corp-partner.google.com>
Reviewed-by: Zhuohao Lee <zhuohao@chromium.org>
Commit-Queue: Keith Short <keithshort@chromium.org>

2 files changed, 54 insertions, 1 deletions

diff --git a/common/i2c_master.c b/common/i2c_master.c
index 36bdf81dd1..048891225c 100644
--- a/common/i2c_master.c
+++ b/common/i2c_master.c
@@ -408,6 +408,42 @@ exit:
 	return rv;
 }
 
+int i2c_read_block(int port, int slave_addr, int offset, uint8_t *data,
+		    int len)
+{
+	int rv;
+	uint8_t reg_address = offset;
+
+	i2c_lock(port, 1);
+	rv = i2c_xfer(port, slave_addr, &reg_address, 1, data, len,
+			I2C_XFER_SINGLE);
+	i2c_lock(port, 0);
+	return rv;
+}
+
+int i2c_write_block(int port, int slave_addr, int offset, const uint8_t *data,
+		    int len)
+{
+	int rv0, rv1;
+	uint8_t reg_address = offset;
+
+	/*
+	 * Split into two transactions to avoid the stack space consumption of
+	 * appending the destination address with the data array.  Even if the
+	 * first transaction fails, unconditionally perform the second one in
+	 * order to have a better chance at sending out the stop bit.
+	 */
+	i2c_lock(port, 1);
+	rv0 = i2c_xfer(port, slave_addr, &reg_address, 1, NULL, 0,
+		      I2C_XFER_START);
+	rv1 = i2c_xfer(port, slave_addr, data, len, NULL, 0,
+		      I2C_XFER_STOP);
+	i2c_lock(port, 0);
+
+	/* Guess that the first error seen is more helpful. */
+	return (rv0 != EC_SUCCESS) ? rv0 : rv1;
+}
+
 int get_sda_from_i2c_port(int port, enum gpio_signal *sda)
 {
 	const struct i2c_port_t *i2c_port = get_i2c_port(port);
diff --git a/include/i2c.h b/include/i2c.h
index 5683898bd6..9b429621ae 100644
--- a/include/i2c.h
+++ b/include/i2c.h
@@ -329,13 +329,30 @@ int i2c_unwedge(int port);
  *
  * <len>      : the max length of receiving buffer. to read N bytes
  *              ascii, len should be at least N+1 to include the
- *              terminating 0.
+ *              terminating 0.  Similar to strlcpy, the terminating null is
+ *              always written into the output buffer.
  * <len> == 0 : buffer size > 255
  */
 int i2c_read_string(int port, int slave_addr, int offset, uint8_t *data,
 			int len);
 
 /**
+ * Read a data block of <len> 8-bit transfers from the slave at 8-bit slave
+ * address <slaveaddr>, at the specified 8-bit <offset> in the slave's address
+ * space.
+ */
+int i2c_read_block(int port, int slave_addr, int offset, uint8_t *data,
+			int len);
+
+/**
+ * Write a data block of <len> 8-bit transfers to the slave at 8-bit slave
+ * address <slaveaddr>, at the specified 8-bit <offset> in the slave's address
+ * space.
+ */
+int i2c_write_block(int port, int slave_addr, int offset, const uint8_t *data,
+			int len);
+
+/**
  * Convert port number to controller number, for multi-port controllers.
  * This function will only be called if CONFIG_I2C_MULTI_PORT_CONTROLLER is
  * defined.