linux-kernel - Re: [PATCH 0/4] HID: debugfs rework

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Message-ID: <516FA648.20207@redhat.com>
Date:	Thu, 18 Apr 2013 09:52:40 +0200
From:	Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:	Jiri Kosina <jkosina@...e.cz>
CC:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Benjamin Tissoires <benjamin.tissoires@...il.com>,
	linux-input@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] HID: debugfs rework

On 04/17/2013 07:44 PM, Jiri Kosina wrote:
> On Wed, 17 Apr 2013, Benjamin Tissoires wrote:
> 
>> Hi Jiri,
>>
>> This is a small rework of the HID debugfs.
>> I encountered a problem with multitouch devices: they have too much usages to
>> fit into the fixed size output buffer of 512.
>> So I digg a little, and end up with those 4 patches.
> 
> Hi Benjamin,
> 
> thanks, I will look into it and see whether I would be able to apply it 
> still for 3.10 merge window.

Thanks. I think patches 1 and 2 of this series are pretty straightforward.
Patches 3 and 4 will maybe require a little bit more attention.

I don't mind if it's postponed to 3.11 (given the long time this has
been broken for devices with big reports).
I just need to access HID debugfs for hid-replay when hidraw does not
send anything. But as I'm also willing to use hid-replay with current
kernels, I still need a way to use the best option (hidraw or hid
debugfs) for current kernels.

> 
> I also have a locking fix for HID-debugfs which I am going to apply 
> shortly, but I am travelling this week, so I am in a bit degraded mode.
> 
> For reference, locking fix below.
> 
> 
> 
> From: Jiri Kosina <jkosina@...e.cz>
> Subject: [PATCH] HID: protect hid_debug_list
> 
> Accesses to hid_device->hid_debug_list are not serialized properly, which
> could result in SMP concurrency issues when HID debugfs events are accessesed

s/accessesed/accessed ?

> by multiple userspace processess.

s/processess/processes ?

> 
> Serialize all the list operations by a mutex.
> 
> Reported-by: Al Viro <viro@...iv.linux.org.uk>
> Signed-off-by: Jiri Kosina <jkosina@...e.cz>

Reviewed-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>

I also have a patch regarding forcing hidraw output even if raw_event
returns > 0, but I'll send it over a new thread. This thread will start
to be quite complicate to follow otherwise... :)

Cheers,
Benjamin
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