linux-kernel - Re: [PATCH 1/2] i2c: Add message transfer tracepoints for I2C [ver #2]

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Message-ID: <20140313211532.GA2696@katana>
Date:	Thu, 13 Mar 2014 22:15:32 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	David Howells <dhowells@...hat.com>
Cc:	wolfram@...-dreams.de, khali@...ux-fr.org,
	linux-i2c@...r.kernel.org, rostedt@...dmis.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] i2c: Add message transfer tracepoints for I2C [ver
 #2]

On Thu, Mar 06, 2014 at 01:35:59PM +0000, David Howells wrote:
> Add tracepoints into the I2C message transfer function to retrieve the message
> sent or received.  The following config options must be turned on to make use
> of the facility:
> 
> 	CONFIG_FTRACE
> 	CONFIG_ENABLE_DEFAULT_TRACERS
> 
> The I2C tracepoint can be enabled thusly:
> 
> 	echo 1 >/sys/kernel/debug/tracing/events/i2c/i2c_transfer/enable
> 
> and will dump messages that can be viewed in /sys/kernel/debug/tracing/trace
> that look like:
> 
> 	... i2c_write: i2c-5 #0 a=044 f=0000 l=2 [02-14]
> 	... i2c_read: i2c-5 #1 a=044 f=0001 l=4
> 	... i2c_reply: i2c-5 #1 a=044 f=0001 l=4 [33-00-00-00]
> 	... i2c_result: i2c-5 n=2 ret=2
> 
> formatted as:
> 
> 	i2c-<adapter-nr>
> 	#<message-array-index>
> 	a=<addr>
> 	f=<flags>
> 	l=<datalen>
> 	n=<message-array-size>
> 	ret=<result>
> 	[<data>]
> 
> The operation is done between the i2c_write/i2c_read lines and the i2c_reply
> and i2c_result lines so that if the hardware hangs, the trace buffer can be
> consulted to determine the problematic operation.
> 
> The adapters to be traced can be selected by something like:
> 
> 	echo adapter_nr==1 >/sys/kernel/debug/tracing/events/i2c/filter
> 
> These changes are based on code from Steven Rostedt.
> 
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: David Howells <dhowells@...hat.com>
> Reviewed-by: Steven Rostedt <rostedt@...dmis.org>

Applied to for-next, thanks!


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