Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net

[linux.git] / Documentation / i2c / i2c-protocol

diff --git a/Documentation/i2c/i2c-protocol b/Documentation/i2c/i2c-protocol
index 0b3e62d1f77a1853765338afd9ed9d6ea56902d2..ff6d6cee6c7e17a684d9cad757f74d719c7bfb82 100644 (file)
--- a/Documentation/i2c/i2c-protocol
+++ b/Documentation/i2c/i2c-protocol
@@ -6,8 +6,8 @@ Key to symbols
 S     (1 bit) : Start bit
 P     (1 bit) : Stop bit
 Rd/Wr (1 bit) : Read/Write bit. Rd equals 1, Wr equals 0.
-A, NA (1 bit) : Accept and reverse accept bit. 
-Addr  (7 bits): I2C 7 bit address. Note that this can be expanded as usual to 
+A, NA (1 bit) : Accept and reverse accept bit.
+Addr  (7 bits): I2C 7 bit address. Note that this can be expanded as usual to
                 get a 10 bit I2C address.
 Comm  (8 bits): Command byte, a data byte which often selects a register on
                 the device.
@@ -49,11 +49,20 @@ a byte read, followed by a byte write:
 Modified transactions
 =====================
 
-The following modifications to the I2C protocol can also be generated,
-with the exception of I2C_M_NOSTART these are usually only needed to
-work around device issues:
+The following modifications to the I2C protocol can also be generated by
+setting these flags for i2c messages. With the exception of I2C_M_NOSTART, they
+are usually only needed to work around device issues:
 
-  Flag I2C_M_NOSTART: 
+I2C_M_IGNORE_NAK:
+    Normally message is interrupted immediately if there is [NA] from the
+    client. Setting this flag treats any [NA] as [A], and all of
+    message is sent.
+    These messages may still fail to SCL lo->hi timeout.
+
+I2C_M_NO_RD_ACK:
+    In a read message, master A/NA bit is skipped.
+
+I2C_M_NOSTART:
     In a combined transaction, no 'S Addr Wr/Rd [A]' is generated at some
     point. For example, setting I2C_M_NOSTART on the second partial message
     generates something like:
@@ -67,17 +76,13 @@ work around device issues:
     I2C device but may also be used between direction changes by some
     rare devices.
 
-  Flags I2C_M_REV_DIR_ADDR
+I2C_M_REV_DIR_ADDR:
     This toggles the Rd/Wr flag. That is, if you want to do a write, but
     need to emit an Rd instead of a Wr, or vice versa, you set this
     flag. For example:
       S Addr Rd [A] Data [A] Data [A] ... [A] Data [A] P
 
-  Flags I2C_M_IGNORE_NAK
-    Normally message is interrupted immediately if there is [NA] from the
-    client. Setting this flag treats any [NA] as [A], and all of
-    message is sent.
-    These messages may still fail to SCL lo->hi timeout.
-
-  Flags I2C_M_NO_RD_ACK
-    In a read message, master A/NA bit is skipped.
+I2C_M_STOP:
+    Force a stop condition (P) after the message. Some I2C related protocols
+    like SCCB require that. Normally, you really don't want to get interrupted
+    between the messages of one transfer.