linux-kernel - Re: [PATCH] toshiba_acpi: Fix keyboard backight sysfs entries not being updated

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Date:	Fri, 20 Nov 2015 16:55:06 -0700
From:	Azael Avalos <coproscefalo@...il.com>
To:	Darren Hart <dvhart@...radead.org>
Cc:	"platform-driver-x86@...r.kernel.org" 
	<platform-driver-x86@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] toshiba_acpi: Fix keyboard backight sysfs entries not
 being updated

Hi Darren,

2015-11-20 16:39 GMT-07:00 Darren Hart <dvhart@...radead.org>:
> On Mon, Nov 16, 2015 at 12:59:31PM -0700, Azael Avalos wrote:
>> Certain Toshiba models with the second generation keyboard backlight
>> (type 2) do not generate the keyboard backlight changed event (0x92),
>> and thus, the sysfs entries are never being updated.
>>
>> This patch adds a workquee and a global boolean variable to address
>> the issue.
>>
>> For those models that do generate the event, the sysfs entries are
>> being updated via the *notify function and the boolean is set to
>> true to avoid a second call to update the entries.
>>
>> For those models that do not generate the event, the workquee is
>> used to update the sysfs entries and also to emulate the event via
>> netlink, to make userspace aware of such change.
>
> Thanks Azael,
>
> Rather than ask you to wait while I research workqueues and their use more, what
> is it about this task that requires a workqueue? Why can we not call what's in
> the workqueue below directly from the kbd_backlight_mode_store sysfs write
> callback?

I used the workquee to let the sysfs *store function to finish w/o affecting
the "refresh" of the sysfs entries.

Previously the sysfs_update_group resided inside the *store function,
but caused a lock everytime the keyboard mode was changed, and the
sysfs entries were never updated, this was fixed by moving such function
to the *notify function, but turns out that some models do not fire such
event.


Cheers
Azael


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