linux-kernel - Re: [RFC,PATCH] i2c: fix device_init

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Message-Id: <200808110903.58658.marc.pignat@hevs.ch>
Date:	Mon, 11 Aug 2008 09:03:58 +0200
From:	Marc Pignat <marc.pignat@...s.ch>
To:	David Brownell <david-b@...bell.net>
Cc:	khali@...ux-fr.org, linux-kernel@...r.kernel.org,
	i2c@...sensors.org
Subject: Re: [RFC,PATCH] i2c: fix device_init_wakeup place

Hi all!

First, I would like to ask David to exuse me for saying something like "your
patch did nothing", it was crude.

David had a real good idea to add the flag I2C_CLIENT_WAKE.

On Monday 11 August 2008, David Brownell wrote:
> > > The current code calls device_init_wakeup() before device_register, but
...
> > Interesting point... David, what are you using this code for then? Same
> > question for you Marc.
...

I use it for an rtc chip (ds1374), but the board is not in tree (should be
soon).

> 
> 
> > > This patch also include a small functionnal change: the I2C_CLIENT_WAKE
> > > is no more removed from the client flags, but this should't hurt.
> >
> > Why do you want to change this?
> 
> It's kind of essential to making this patch work!  Else the flag
> won't be available when the i2c core gets control of that device
> node again, after device_initialize() code zeroes those flags.

Now the flag is used in the i2c_device_probe function and must be preserved
for future use (probe of another device or re-probe).

The downside is that it make this flag visible to the i2c_client.

To preserve the original behavior (hide the flag to the driver), the flag
should be saved, for instance in the i2c_device structure.
I think adding more code and adding a field in the i2c_device structure costs
more than making this flag visible (but if you think differently, I can fix the
patch).

> 
> 
...
> Better would be to preserve any existing settings:
> 
> 	if (!device_can_wakeup(&client->dev))
> 		device_init_wakeup(...)
> 
> That way the userspace policy setting is preserved unless the
> device itself gets removed ... instead of being clobbered by
> the simple act of (re)probing a driver.
Ok, will be fixed in version 2

Best regards

Marc
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