linux-kernel - Re: [PATCH] PM / wakeup: Avoid dev

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Date:   Mon, 29 Jul 2019 07:07:19 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Tri Vo <trong@...roid.com>,
        Kalesh Singh <kaleshsingh@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>
Subject: Re: [PATCH] PM / wakeup: Avoid dev_name collisions in wakeup class

Quoting Rafael J. Wysocki (2019-07-27 06:10:00)
> On Sat, Jul 27, 2019 at 3:11 AM Stephen Boyd <swboyd@...omium.org> wrote:
> >
> > If a device is wakeup capable and the driver calls device_wakeup_init()
> > on it during probe and then userspace writes 'enabled' to that device's
> > power/wakeup file in sysfs we'll try to create the same named wakeup
> > device in sysfs. The kernel will complain about duplicate file names.
> >
> > sysfs: cannot create duplicate filename '/devices/virtual/wakeup/1-1.1'
> > kobject_add_internal failed for 1-1.1 with -EEXIST, don't try to register things with the same name in the same directory.
> >
> > It may be advantageous to not write 'enabled' to the wakeup file (see
> > wakeup_store()) from userspace for these devices because we allocate
> > devices and register them and then throw them all away later on if the
> > device driver has already initialized the wakeup attribute. The
> > implementation currently tries to avoid taking locks here so it seems
> > best to optimize that path in a separate patch.
> >
> > Let's rename the wakeup class devices as 'wakeupN' with an IDA that's
> > simple enough to just return some sort of number. In addition, let's
> > make the device registering the wakeup the parent and include a 'name'
> > attribute in case userspace wants to figure out the type of wakeup it is
> > (in the case of virtual wakeups) or the device associated with the
> > wakeup. This makes it easier for userspace to go from /sys/class/wakeup
> > to a place in the device hierarchy where the wakeup is generated from
> > like an input device.
> >
> > Cc: Tri Vo <trong@...roid.com>
> > Cc: Kalesh Singh <kaleshsingh@...gle.com>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Cc: Ravi Chandra Sadineni <ravisadineni@...omium.org>
> > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> 
> I'd rather change the commit that introduced this issue which is only
> in linux-next for now.

Feel free to squash the two patches together and throw my signed-off-by
on it. I forgot to add 'name' to the Documentation directory. Here's
something to that effect.

-----8<-----
diff --git a/Documentation/ABI/testing/sysfs-class-wakeup b/Documentation/ABI/testing/sysfs-class-wakeup
index 30fb23eb9112..b83a87380d2c 100644
--- a/Documentation/ABI/testing/sysfs-class-wakeup
+++ b/Documentation/ABI/testing/sysfs-class-wakeup
@@ -5,6 +5,13 @@ Description:
 		The /sys/class/wakeup/ directory contains pointers to all
 		wakeup sources in the kernel at that moment in time.
 
+What:		/sys/class/wakeup/.../name
+Date:		June 2019
+Contact:	Tri Vo <trong@...roid.com>
+Description:
+		This file contains the name of the wakeup source when
+		it was created.
+
 What:		/sys/class/wakeup/.../active_count
 Date:		June 2019
 Contact:	Tri Vo <trong@...roid.com>