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Commit 9f02fba8 authored by Wolfram Sang's avatar Wolfram Sang
Browse files

Documentation: i2c: improve section about flags mangling the protocol 



Sort the entries alphabetically. Make the introductory paragraph more
precise. Skip useless 'Flag' introduction from the entries. Remove
trailing white spaces from the file. Add missing I2C_M_STOP entry.

Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent cf23e335

Documentation/i2c/i2c-protocol

+20 −15
Original line number Diff line number Diff line
@@ -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.