linux-kernel - Re: [PATCH] i2c: allow specifying separate wakeup interrupt in device tree

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 19 Aug 2015 19:43:49 +0200
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Vignesh R <vigneshr@...com>, Tony Lindgren <tony@...mide.com>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: allow specifying separate wakeup interrupt in
 device tree


> > > > @@ -659,20 +662,47 @@ static int i2c_device_probe(struct device *dev)
> > > >  	if (!device_can_wakeup(&client->dev))
> > > >  		device_init_wakeup(&client->dev,
> > > >  					client->flags & I2C_CLIENT_WAKE);
> > > 
> > > I was about to ask if we couldn't combine this and the later if-blocks
> > > with an if-else combination. But now I stumble over the above block in
> > > general: If the device cannot cause wake ups, then we might initialize
> > > it as a wakeup-device depending on client->flags??
> > 
> > I believe it is done so that we do not try to re-add wakeup source after
> > unbinding/rebinding the device. With my patch we clearing wakeup flag on
> > unbind, so it is OK, but there is still error path where we might want
> > to reset the wakeup flag as well.
> 
> I was wondering if it wants to achieve that, why does it not
> unconditionally use 0 instead of the WAKE flag.

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?

Thanks,

   Wolfram

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/