smart battery: Fix mfgacc access function reading wrong number of bytes

`sb_read_mfgacc` currently uses `sb_read_string`. This function reads a
null-terminated string. However, the data that is being read is not a
null-terminated string. This is causing N-1 bytes to be read instead of
N bytes. This commit adds an `sb_read_sized_block` function that is used
instead. Only PARAM_SAFETY_STATUS and PARAM_OPERATION_STATUS are read
with `sb_read_mfgacc` and neither of these values are a string.

BUG=b:228589840
TEST=Ran i2ctrace to verify that right number of bytes are now being
read, tested with CL:3578293 to ensure no errors
BRANCH=guybrush

Change-Id: Iaedb4d28274bda8b6d1ee6d2021ebd04f83767f8
Signed-off-by: Robert Zieba <robertzieba@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3606146
Reviewed-by: Rob Barnes <robbarnes@google.com>
Reviewed-by: Diana Z <dzigterman@chromium.org>
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>

2 files changed, 37 insertions, 3 deletions

diff --git a/driver/battery/smart.c b/driver/battery/smart.c
index 62a7d61258..c87a1a6cdc 100644
--- a/driver/battery/smart.c
+++ b/driver/battery/smart.c
@@ -92,7 +92,28 @@ int sb_read_string(int offset, uint8_t *data, int len)
 	if (battery_supports_pec())
 		addr_flags |= I2C_FLAG_PEC;
 
-	return i2c_read_string(I2C_PORT_BATTERY, addr_flags, offset, data, len);
+	return i2c_read_string(I2C_PORT_BATTERY, addr_flags, offset, data,
+			       len);
+}
+
+int sb_read_sized_block(int offset, uint8_t *data, int len)
+{
+	uint16_t addr_flags = BATTERY_ADDR_FLAGS;
+	int read_len = 0;
+
+	if (IS_ENABLED(CONFIG_BATTERY_CUT_OFF)) {
+		/*
+		 * Some batteries would wake up after cut-off if we talk to it.
+		 */
+		if (battery_is_cut_off())
+			return EC_RES_ACCESS_DENIED;
+	}
+
+	if (battery_supports_pec())
+		addr_flags |= I2C_FLAG_PEC;
+
+	return i2c_read_sized_block(I2C_PORT_BATTERY, addr_flags, offset, data,
+				    len, &read_len);
 }
 
 int sb_read_mfgacc(int cmd, int block, uint8_t *data, int len)
@@ -116,7 +137,7 @@ int sb_read_mfgacc(int cmd, int block, uint8_t *data, int len)
 	 * First two bytes returned are command sent,
 	 * rest are actual data LSB to MSB.
 	 */
-	rv = sb_read_string(block, data, len);
+	rv = sb_read_sized_block(block, data, len);
 	if (rv)
 		return rv;
 	if ((data[0] | data[1] << 8) != cmd)
diff --git a/include/battery_smart.h b/include/battery_smart.h
index b97d681223..9b373f7c8a 100644
--- a/include/battery_smart.h
+++ b/include/battery_smart.h
@@ -169,9 +169,22 @@
 /* Read from battery */
 int sb_read(int cmd, int *param);
 
-/* Read sequence from battery */
+/**
+ * Read null-terminated string from battery
+ * @param offset	Battery register to read from
+ * @param data		Buffer to hold the string
+ * @param len		Length of data buffer
+ */
 int sb_read_string(int offset, uint8_t *data, int len);
 
+/**
+ * Read sized block of data from battery
+ * @param offset	Battery register to read from
+ * @param data		Buffer to hold read data
+ * @param len		Length of data buffer
+ */
+int sb_read_sized_block(int offset, uint8_t *data, int len);
+
 /* Write to battery */
 int sb_write(int cmd, int param);