linux-kernel - Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

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Date:	Thu, 29 Apr 2010 16:41:57 -0700
From:	Arve Hjønnevåg <arve@...roid.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	linux-pm@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
	Alan Stern <stern@...land.harvard.edu>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ryusuke Konishi <konishi.ryusuke@....ntt.co.jp>,
	Jim Collar <jim.collar@...are.net>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Avi Kivity <avi@...hat.com>, Len Brown <len.brown@...el.com>,
	Pavel Machek <pavel@....cz>, Magnus Damm <damm@...l.co.jp>,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	Nigel Cunningham <nigel@...onice.net>,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend 
	blockers from user-space

2010/4/29 Rafael J. Wysocki <rjw@...k.pl>:
> On Thursday 29 April 2010, Arve Hjønnevåg wrote:
>> 2010/4/28 Rafael J. Wysocki <rjw@...k.pl>:
>> > On Thursday 29 April 2010, Arve Hjønnevåg wrote:
>> >> 2010/4/28 Rafael J. Wysocki <rjw@...k.pl>:
>> >> > On Wednesday 28 April 2010, Arve Hjønnevåg wrote:
>> >> >> Add a misc device, "suspend_blocker", that allows user-space processes
>> >> >> to block auto suspend. The device has ioctls to create a suspend_blocker,
>> >> >> and to block and unblock suspend. To delete the suspend_blocker, close
>> >> >> the device.
>> >> >>
>> >> >> Signed-off-by: Arve Hjønnevåg <arve@...roid.com>
>> >> > ...
>> >> >> +
>> >> >> +#include <linux/fs.h>
>> >> >> +#include <linux/miscdevice.h>
>> >> >> +#include <linux/module.h>
>> >> >> +#include <linux/uaccess.h>
>> >> >> +#include <linux/slab.h>
>> >> >> +#include <linux/suspend_blocker.h>
>> >> >> +#include <linux/suspend_block_dev.h>
>> >> >> +
>> >> >> +enum {
>> >> >> +     DEBUG_FAILURE   = BIT(0),
>> >> >> +};
>> >> >> +static int debug_mask = DEBUG_FAILURE;
>> >> >
>> >> > What's the exact purpose of this?
>> >>
>> >> To show errors returned to user space. I can turn it off by default if you want.
>> >
>> > Not necessarily, but why is it a mask?  It looks like a 0/1 thing would be
>> > sufficient.
>>
>> I may want to add a bit to print all user-space block and unblock calls.
>
> Alternatively, you can add a new parameter for that, which I think I would prefer.
>

I use a bit-mask in the main suspend blocker code. This makes it easy
to turn on or off all the messages.

-- 
Arve Hjønnevåg
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