Re: [PATCH] i2c: allow specifying separate wakeup interrupt in device tree
From: Wolfram Sang
Date: Mon Aug 24 2015 - 08:34:12 EST
> > When reviewing V2, I wasn't comfortable with just guessing what the old
> > code means. So, I did some digging and found:
> > https://lkml.org/lkml/2008/8/10/204
> > Quoting the interesting paragraph from David Brownell:
> > ===
> > 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.
> >> > + device_init_wakeup(&client->dev, client->flags &
> >> > I2C_CLIENT_WAKE);
> > ===
> > I have to admit that I am not familiar with device wakeup handling and
> > especially its userspace policies. Can you double check that your V2
> > meets the above intention?
> No it does not; it explicitly resets the wakeup flag. Note that the
> original code was not quite right in that regard either: it would
> preserve wakeup flag set by userspace upon driver rebinding; but it
> would re-arm the wakeup flag if it was disabled by userspace.
> I believe that resetting the flag upon re-binding the driver is proper
> behavior as the driver is responsible for setting up and handling
Okay, that meets my idea of how this should work. I rephrased the above
paragraph slightly and added it to the commit message of V2.
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