Add support for short writes with PEC.

git-svn-id: http://lm-sensors.org/svn/i2c-tools/trunk@5771 7894878c-1315-0410-8ee3-d5d059ff63e0

CHANGES

@@ -14,6 +14,7 @@ SVN
                 Decode voltage interface level of DDR SDRAM
   decode-xeon: Delete
   eepromer: Fix array initialization overrun
+  i2cset: Add support for short writes with PEC
   i2c-stub-from-dump: Use udev settle to speed up initialization
 
 3.0.2 (2008-11-29)

tools/i2cset.8

@@ -11,7 +11,8 @@ i2cset \- set I2C registers
 .I i2cbus
 .I chip-address
 .I data-address
-.RI [ "value " [ "mode" ]]
+.RI [ value ]
+.RI [ mode ]
 .br
 .B i2cset
 .B -V
@@ -73,6 +74,9 @@ respectively. A \fBp\fP can also be appended to the \fImode\fR parameter to
 enable PEC. If the \fImode\fR parameter is omitted, i2cset defaults to byte
 mode without PEC. The \fIvalue\fR provided must be within range for the
 specified data type (0x00-0xFF for bytes, 0x0000-0xFFFF for words).
+Another possible mode is \fBc\fP, which doesn't write any value (so-called
+short write). You usually don't have to specify this mode, as it is the
+default when no value is provided, unless you also want to enable PEC.
 
 .SH WARNING
 i2cset can be extremely dangerous if used improperly. It can confuse your

tools/i2cset.c

@@ -2,7 +2,7 @@
     i2cset.c - A user-space program to write an I2C register.
     Copyright (C) 2001-2003  Frodo Looijaard <frodol@dds.nl>, and
                              Mark D. Studebaker <mdsxyz123@yahoo.com>
-    Copyright (C) 2004-2008  Jean Delvare <khali@linux-fr.org>
+    Copyright (C) 2004-2009  Jean Delvare <khali@linux-fr.org>
 
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -35,12 +35,13 @@ static void help(void) __attribute__ ((noreturn));
 static void help(void)
 {
 	fprintf(stderr,
-	        "Usage: i2cset [-f] [-y] [-m MASK] I2CBUS CHIP-ADDRESS DATA-ADDRESS [VALUE [MODE]]\n"
+	        "Usage: i2cset [-f] [-y] [-m MASK] I2CBUS CHIP-ADDRESS DATA-ADDRESS [VALUE] [MODE]\n"
 		"  I2CBUS is an integer or an I2C bus name\n"
 		"  ADDRESS is an integer (0x03 - 0x77)\n"
 		"  MODE is one of:\n"
-		"    b (byte, default)\n"
-		"    w (word)\n"
+		"    c (byte, no value)\n"
+		"    b (byte data, default)\n"
+		"    w (word data)\n"
 		"    Append p for SMBus PEC\n");
 	exit(1);
 }
@@ -180,11 +181,18 @@ int main(int argc, char *argv[])
 	}
 
 	if (argc > flags + 4) {
-		size = I2C_SMBUS_BYTE_DATA;
-		value = strtol(argv[flags+4], &end, 0);
-		if (*end || value < 0) {
-			fprintf(stderr, "Error: Data value invalid!\n");
-			help();
+		if (!strcmp(argv[flags+4], "c")
+		 || !strcmp(argv[flags+4], "cp")) {
+			size = I2C_SMBUS_BYTE;
+			value = -1;
+			pec = argv[flags+4][1] == 'p';
+		} else {
+			size = I2C_SMBUS_BYTE_DATA;
+			value = strtol(argv[flags+4], &end, 0);
+			if (*end || value < 0) {
+				fprintf(stderr, "Error: Data value invalid!\n");
+				help();
+			}
 		}
 	} else {
 		size = I2C_SMBUS_BYTE;