Perform I2C transmission in a single burst when mode is "none" or not set

Some more automated I2C controllers cannot explicitly create
START/STOP/etc. conditions on the bus.
Instead, the correct condition is set automatically according
to the pending transfer status.
This particular behavior can cause trouble if some I2C slave
requires sending address offset within the chip followed by
the actual data or command. In that case we cannot assume that
the driver will not STOP immediately after sending
offset.

To avoid that, do not split offset transfer from data transfer
for default transmission modes and do exactly that if requested
in command line (stop-start and repeated-start modes).
This more generic approach should cover special cases like
the one described.

Reviewed by:   imp
Submitted by:  Marcin Mazurek <mma@semihalf.com>
Obtained from: Semihalf

1 files changed, 79 insertions, 28 deletions

diff --git a/usr.sbin/i2c/i2c.c b/usr.sbin/i2c/i2c.c
index 920dda2..3021b86 100644
--- a/usr.sbin/i2c/i2c.c
+++ b/usr.sbin/i2c/i2c.c
@@ -280,9 +280,6 @@ i2c_write(char *dev, struct options i2c_opt, char *i2c_buf)
 		err(1, "open failed");
 	}
 
-	/*
-	 * Write offset where the data will go
-	 */
 	cmd.slave = i2c_opt.addr;
 	error = ioctl(fd, I2CSTART, &cmd);
 	if (error == -1) {
@@ -297,20 +294,24 @@ i2c_write(char *dev, struct options i2c_opt, char *i2c_buf)
 			err_msg = "error: offset malloc";
 			goto err1;
 		}
+	}
 
-		cmd.count = bufsize;
-		cmd.buf = buf;
-		error = ioctl(fd, I2CWRITE, &cmd);
-		free(buf);
-		if (error == -1) {
-			err_msg = "ioctl: error when write offset";
-			goto err1;
+	switch(i2c_opt.mode) {
+	case I2C_MODE_STOP_START:
+		/*
+		 * Write offset where the data will go
+		 */
+		if (i2c_opt.width) {
+			cmd.count = bufsize;
+			cmd.buf = buf;
+			error = ioctl(fd, I2CWRITE, &cmd);
+			free(buf);
+			if (error == -1) {
+				err_msg = "ioctl: error when write offset";
+				goto err1;
+			}
 		}
-	}
 
-	/* Mode - stop start */
-	if (i2c_opt.mode == I2C_MODE_STOP_START) {
-		cmd.slave = i2c_opt.addr;
 		error = ioctl(fd, I2CSTOP, &cmd);
 		if (error == -1) {
 			err_msg = "ioctl: error sending stop condition";
@@ -322,9 +323,35 @@ i2c_write(char *dev, struct options i2c_opt, char *i2c_buf)
 			err_msg = "ioctl: error sending start condition";
 			goto err1;
 		}
-	}
-	/* Mode - repeated start */
-	if (i2c_opt.mode == I2C_MODE_REPEATED_START) {
+
+		/*
+		 * Write the data
+		 */
+		cmd.count = i2c_opt.count;
+		cmd.buf = i2c_buf;
+		cmd.last = 0;
+		error = ioctl(fd, I2CWRITE, &cmd);
+		if (error == -1) {
+			err_msg = "ioctl: error when write";
+			goto err1;
+		}
+		break;
+
+	case I2C_MODE_REPEATED_START:
+		/*
+		 * Write offset where the data will go
+		 */
+		if (i2c_opt.width) {
+			cmd.count = bufsize;
+			cmd.buf = buf;
+			error = ioctl(fd, I2CWRITE, &cmd);
+			free(buf);
+			if (error == -1) {
+				err_msg = "ioctl: error when write offset";
+				goto err1;
+			}
+		}
+
 		cmd.slave = i2c_opt.addr;
 		error = ioctl(fd, I2CRPTSTART, &cmd);
 		if (error == -1) {
@@ -332,18 +359,42 @@ i2c_write(char *dev, struct options i2c_opt, char *i2c_buf)
 			    "condition";
 			goto err1;
 		}
-	}
 
-	/*
-	 * Write the data
-	 */
-	cmd.count = i2c_opt.count;
-	cmd.buf = i2c_buf;
-	cmd.last = 0;
-	error = ioctl(fd, I2CWRITE, &cmd);
-	if (error == -1) {
-		err_msg = "ioctl: error when write";
-		goto err1;
+		/*
+		 * Write the data
+		 */
+		cmd.count = i2c_opt.count;
+		cmd.buf = i2c_buf;
+		cmd.last = 0;
+		error = ioctl(fd, I2CWRITE, &cmd);
+		if (error == -1) {
+			err_msg = "ioctl: error when write";
+			goto err1;
+		}
+		break;
+
+	case I2C_MODE_NONE: /* fall through */
+	default:		
+		buf = realloc(buf, bufsize + i2c_opt.count);
+		if (buf == NULL) {
+			err_msg = "error: data malloc";
+			goto err1;
+		}
+
+		memcpy(buf + bufsize, i2c_buf, i2c_opt.count);
+		/*
+		 * Write offset and data
+		 */
+		cmd.count = bufsize + i2c_opt.count;
+		cmd.buf = buf;
+		cmd.last = 0;
+		error = ioctl(fd, I2CWRITE, &cmd);
+		free(buf);
+		if (error == -1) {
+			err_msg = "ioctl: error when write";
+			goto err1;
+		}
+		break;
 	}
 	cmd.slave = i2c_opt.addr;
 	error = ioctl(fd, I2CSTOP, &cmd);