Support and use the new I2C block read with variable length which will

be available in Linux kernel 2.6.23. Binary compatibility is guaranteed,
source code compatibility isn't, but the incompatibility will be
spotted quickly as the prototype of the helper function
i2c_smbus_read_i2c_block_data() changed. The only problem would be if
a program is calling i2c_smbus_access() directly. Hopefully this should
be a rare case. The py-smbus binding code is in this case and will be
adjusted soon.


git-svn-id: http://lm-sensors.org/svn/lm-sensors/trunk@4417 7894878c-1315-0410-8ee3-d5d059ff63e0

kernel/include/i2c-dev.h

@@ -106,8 +106,9 @@ union i2c_smbus_data {
 #define I2C_SMBUS_WORD_DATA	    3
 #define I2C_SMBUS_PROC_CALL	    4
 #define I2C_SMBUS_BLOCK_DATA	    5
-#define I2C_SMBUS_I2C_BLOCK_DATA    6
+#define I2C_SMBUS_I2C_BLOCK_BROKEN  6
 #define I2C_SMBUS_BLOCK_PROC_CALL   7		/* SMBus 2.0 */
+#define I2C_SMBUS_I2C_BLOCK_DATA    8
 
 
 /* ----- commands for the ioctl like i2c_command call:
@@ -271,12 +272,20 @@ static inline __s32 i2c_smbus_write_block_data(int file, __u8 command,
 }
 
 /* Returns the number of read bytes */
+/* Until kernel 2.6.22, the length is hardcoded to 32 bytes. If you
+   ask for less than 32 bytes, your code will only work with kernels
+   2.6.23 and later. */
 static inline __s32 i2c_smbus_read_i2c_block_data(int file, __u8 command,
-                                                  __u8 *values)
+                                                  __u8 length, __u8 *values)
 {
 	union i2c_smbus_data data;
 	int i;
+
+	if (length > 32)
+		length = 32;
+	data.block[0] = length;
 	if (i2c_smbus_access(file,I2C_SMBUS_READ,command,
+	                     length == 32 ? I2C_SMBUS_I2C_BLOCK_BROKEN :
 	                      I2C_SMBUS_I2C_BLOCK_DATA,&data))
 		return -1;
 	else {
@@ -297,7 +306,7 @@ static inline __s32 i2c_smbus_write_i2c_block_data(int file, __u8 command,
 		data.block[i] = values[i-1];
 	data.block[0] = length;
 	return i2c_smbus_access(file,I2C_SMBUS_WRITE,command,
-	                        I2C_SMBUS_I2C_BLOCK_DATA, &data);
+	                        I2C_SMBUS_I2C_BLOCK_BROKEN, &data);
 }
 
 /* Returns the number of read bytes */