linux-kernel - Re: [PATCH] i2c: Add message transfer tracepoints for I2C and SMBUS

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Message-ID: <20131213175350.0c4a95d5@endymion.delvare>
Date:	Fri, 13 Dec 2013 17:53:50 +0100
From:	Jean Delvare <khali@...ux-fr.org>
To:	David Howells <dhowells@...hat.com>
Cc:	linux-i2c@...r.kernel.org, rostedt@...dmis.org,
	linux-kernel@...r.kernel.org, Wolfram Sang <wolfram@...-dreams.de>
Subject: Re: [PATCH] i2c: Add message transfer tracepoints for I2C and SMBUS

On Fri, 13 Dec 2013 16:05:36 +0000, David Howells wrote:
> Jean Delvare <khali@...ux-fr.org> wrote:
> 
> > One significant difference between both implementations is that the old
> > one logs before the actual transfer, while yours logs afterward. While I
> > understand this allows you to log the result of the transfer, this also
> > means you'll miss the log if the actual transaction locks the system
> > (we've seen this before.) Something to think about...
> 
> I could split each into three messages:
> 
> 	- Write request (has params & data buffer)
> 	- Read request (has params but no data buffer)
> 	- Read reply (has data buffer only)
> 
> It will make the transfer functions more complex, though, and will mean that,
> for i2c, you won't get all the replies to the messages in a batch in with the
> requests.  I can also label the messages with the index number.  Mostly I
> suspect this won't be a problem.

Fine with me, we can leave it as is and revisit if it ever is a
problem in practice.

-- 
Jean Delvare
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