Re: [PATCH 2/3] i2c/pxa: only define 'blue_murder'-function if DEBUG is #defined

[Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>]

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Sorry to bump this old thread, it dropped off my todo-list :(

On Sun, Feb 28, 2010 at 03:55:02PM +0000, Russell King - ARM Linux wrote:
> On Wed, Feb 24, 2010 at 12:01:45PM +0100, Uwe Kleine-König wrote:
> > From: Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
> > 
> > This talkative function is also called on timeouts. As timeouts can
> > happen on regular writes to EEPROMs (no error case), this creates false
> > positives.  Giving lots of details is interesting only for developers
> > anyhow, so just use the function if DEBUG is #defined.
> 
> Are you sure this is safe?  If you time out the write before it completes,
> how do you know if the write was successful?
> 
> I don't think this is "no error code" nor "false positive".  If the timeout
> is too short for your EEPROMs, then the timeout needs to be increased.

I am sure this is safe because we have retries. The eeprom driver first tries
to write data without a delay, because EEPROMs often have buffers. Once the
buffers are full, the chip will not answer to the next write request which will
result in a timeout for this write request. This is expected, so it will be
retried after some delay. Something like -EBUSY. Only if another "outer"
timeout passed after some retries, then we have a problem and this should be
user visible. But the timeout for the write request is nothing exceptional and
the user doesn't need to be informed about it, especially not in this detail.
This is what the patch is addressing.

Kind regards,

   Wolfram

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