Re: Dell Vostro V131 hotkeys revisited

["Pali Rohár" <pali.rohar@gmail.com>]

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On Saturday 19 December 2015 01:02:53 Darren Hart wrote:
> On Thu, Dec 17, 2015 at 07:54:35PM +0100, Hans de Goede wrote:
> > Hi,
> > 
> > On 17-12-15 19:47, Pali Rohár wrote:
> > >Hi Hans! See my comments below about your patches.
> 
> ...
> 
> > >>@@ -159,7 +157,8 @@ static void dell_wmi_process_key(int
> > >>reported_key)
> > >>
> > >>  	/* Don't report brightness notifications that will also come
> > >>  	via ACPI */ if ((key->keycode == KEY_BRIGHTNESSUP ||
> > >>
> > >>-	     key->keycode == KEY_BRIGHTNESSDOWN) && acpi_video)
> > >>+	     key->keycode == KEY_BRIGHTNESSDOWN) &&
> > >>+	    acpi_video_handles_brightness_key_presses())
> > >
> > >I do not like this, because that function uses mutex and is called
> > >every time when brightness key event is received by wmi notify
> > >handler.
> > 
> > Right and this is going to happen 1000-s of times a second so is
> > really going to be a performance problem (not).
> > 
> > We cannot cache the return value as was being done before because
> > it can change during startup depending in module loading order
> > (the old code actually got this somewhat wrong), and taking a
> > mutex in a code-path which gets executed only once a second tops
> > is really a non issue.
> 
> Right, this is not a hot path, so the mutex is, indeed, not an issue.

Ok.

-- 
Pali Rohár
pali.rohar@gmail.com

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