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-rw-r--r--Documentation/i2c/smbus-protocol40
1 files changed, 31 insertions, 9 deletions
diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol
index 49f5b680809..d1f22618e14 100644
--- a/Documentation/i2c/smbus-protocol
+++ b/Documentation/i2c/smbus-protocol
@@ -23,6 +23,12 @@ don't match these function names. For some of the operations which pass a
single data byte, the functions using SMBus protocol operation names execute
a different protocol operation entirely.
+Each transaction type corresponds to a functionality flag. Before calling a
+transaction function, a device driver should always check (just once) for
+the corresponding functionality flag to ensure that the underlying I2C
+adapter supports the transaction in question. See
+<file:Documentation/i2c/functionality> for the details.
+
Key to symbols
==============
@@ -49,6 +55,8 @@ This sends a single bit to the device, at the place of the Rd/Wr bit.
A Addr Rd/Wr [A] P
+Functionality flag: I2C_FUNC_SMBUS_QUICK
+
SMBus Receive Byte: i2c_smbus_read_byte()
==========================================
@@ -60,6 +68,8 @@ the previous SMBus command.
S Addr Rd [A] [Data] NA P
+Functionality flag: I2C_FUNC_SMBUS_READ_BYTE
+
SMBus Send Byte: i2c_smbus_write_byte()
========================================
@@ -69,6 +79,8 @@ to a device. See Receive Byte for more information.
S Addr Wr [A] Data [A] P
+Functionality flag: I2C_FUNC_SMBUS_WRITE_BYTE
+
SMBus Read Byte: i2c_smbus_read_byte_data()
============================================
@@ -78,6 +90,8 @@ The register is specified through the Comm byte.
S Addr Wr [A] Comm [A] S Addr Rd [A] [Data] NA P
+Functionality flag: I2C_FUNC_SMBUS_READ_BYTE_DATA
+
SMBus Read Word: i2c_smbus_read_word_data()
============================================
@@ -88,6 +102,8 @@ byte. But this time, the data is a complete word (16 bits).
S Addr Wr [A] Comm [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P
+Functionality flag: I2C_FUNC_SMBUS_READ_WORD_DATA
+
Note the convenience function i2c_smbus_read_word_swapped is
available for reads where the two data bytes are the other way
around (not SMBus compliant, but very popular.)
@@ -102,6 +118,8 @@ the Read Byte operation.
S Addr Wr [A] Comm [A] Data [A] P
+Functionality flag: I2C_FUNC_SMBUS_WRITE_BYTE_DATA
+
SMBus Write Word: i2c_smbus_write_word_data()
==============================================
@@ -112,6 +130,8 @@ specified through the Comm byte.
S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A] P
+Functionality flag: I2C_FUNC_SMBUS_WRITE_WORD_DATA
+
Note the convenience function i2c_smbus_write_word_swapped is
available for writes where the two data bytes are the other way
around (not SMBus compliant, but very popular.)
@@ -126,6 +146,8 @@ This command selects a device register (through the Comm byte), sends
S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A]
S Addr Rd [A] [DataLow] A [DataHigh] NA P
+Functionality flag: I2C_FUNC_SMBUS_PROC_CALL
+
SMBus Block Read: i2c_smbus_read_block_data()
==============================================
@@ -137,6 +159,8 @@ of data is specified by the device in the Count byte.
S Addr Wr [A] Comm [A]
S Addr Rd [A] [Count] A [Data] A [Data] A ... A [Data] NA P
+Functionality flag: I2C_FUNC_SMBUS_READ_BLOCK_DATA
+
SMBus Block Write: i2c_smbus_write_block_data()
================================================
@@ -147,6 +171,8 @@ Comm byte. The amount of data is specified in the Count byte.
S Addr Wr [A] Comm [A] Count [A] Data [A] Data [A] ... [A] Data [A] P
+Functionality flag: I2C_FUNC_SMBUS_WRITE_BLOCK_DATA
+
SMBus Block Write - Block Read Process Call
===========================================
@@ -160,6 +186,8 @@ This command selects a device register (through the Comm byte), sends
S Addr Wr [A] Comm [A] Count [A] Data [A] ...
S Addr Rd [A] [Count] A [Data] ... A P
+Functionality flag: I2C_FUNC_SMBUS_BLOCK_PROC_CALL
+
SMBus Host Notify
=================
@@ -229,15 +257,7 @@ designated register that is specified through the Comm byte.
S Addr Wr [A] Comm [A]
S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P
-
-I2C Block Read (2 Comm bytes)
-=============================
-
-This command reads a block of bytes from a device, from a
-designated register that is specified through the two Comm bytes.
-
-S Addr Wr [A] Comm1 [A] Comm2 [A]
- S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P
+Functionality flag: I2C_FUNC_SMBUS_READ_I2C_BLOCK
I2C Block Write: i2c_smbus_write_i2c_block_data()
@@ -249,3 +269,5 @@ Comm byte. Note that command lengths of 0, 2, or more bytes are
supported as they are indistinguishable from data.
S Addr Wr [A] Comm [A] Data [A] Data [A] ... [A] Data [A] P
+
+Functionality flag: I2C_FUNC_SMBUS_WRITE_I2C_BLOCK