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Commit a1681781 authored by Jean Delvare's avatar Jean Delvare Committed by Jean Delvare
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i2c: Mention functionality flags in SMBus protocol documentation 



While the mapping between I2C adapter functionality flags and
i2c_smbus_*() helper functions is rather obvious, let's still document
it for clarity.

Also drop the reference to 2 command byte I2C block reads, there is no
support for that in the kernel at the moment.

Signed-off-by: default avatarJean Delvare <khali@linux-fr.org>
parent 8117e41e

Documentation/i2c/smbus-protocol

+31 −9
Original line number Diff line number Diff line
@@ -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