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From: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
To: linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Cc: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
Subject: [PATCH] Documentation: i2c: improve section about flags mangling the protocol
Date: Sun,  6 Apr 2014 13:49:32 +0200	[thread overview]
Message-ID: <1396784972-3965-1-git-send-email-wsa@the-dreams.de> (raw)

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: Wolfram Sang <wsa-z923LK4zBo2bacvFa/9K2g@public.gmane.org>
---
 Documentation/i2c/i2c-protocol | 35 ++++++++++++++++++++---------------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/Documentation/i2c/i2c-protocol b/Documentation/i2c/i2c-protocol
index 0b3e62d1f77a..ff6d6cee6c7e 100644
--- 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.
-- 
1.9.1

                 reply	other threads:[~2014-04-06 11:49 UTC|newest]

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