Date:   Mon, 6 Mar 2017 10:18:54 +1030
From:   Jonathan Woithe <jwoithe@...t42.net>
To:     Micha?? K??pie?? <kernel@...pniu.pl>
Cc:     Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/4] fujitsu_init() cleanup

Hi Michael

On Sat, Mar 04, 2017 at 12:17:23PM +1030, Jonathan Woithe wrote:
> On Wed, Mar 01, 2017 at 09:10:40AM +0100, Micha?? K??pie?? wrote:
> > These patches should make fujitsu_init() a bit more palatable.  No
> > changes are made to platform device code yet, for clarity these will be
> > posted in a separate series after this one gets applied.
> 
> I have a preliminary report.  The backlight functionality remains functional
> on an S7020 across all four of the patches in this series and with the
> additional 2-patch cleanup series applied.
> 
> With regard to patch 2/4 you wrote:
> > Jonathan, this *really* needs testing on relevant hardware.  After
> > applying this patch, you should be able to turn LCD backlight on and off
> > using /sys/class/backlight/fujitsu-laptop/bl_power.  Also, the value
> > returned by that attribute upon read should be in sync with actual
> > backlight state even right after loading the module (i.e. before writing
> > anything to bl_power).  Please let me know if any of the above is not
> > true and the module works correctly without this patch applied.
> 
> With patch 2/4 applied:
> 
>  * It is possible to read bl_power
> 
>  * It is possible to write a value to bl_power and read that value back
> 
>  * Writing values to bl_power does not appear to affect the LCD panel in 
>    any way.  That is, the backlight remains unchanged regardless of the 
>    value written.
> 
>  * Behaviour is the same both under X and from the terminal.
> 
> Backing out patch 2/4 but with all others still in place, resulted in no
> change in behaviour.  So while bl_power had no effect with patch 2/4 in
> place, it seems that patch 2/4 is *not* the cause of this.
> 
> I shall run some more bl_power tests and complete a review of the code later
> this weekend.

I have completed a review of the code in this patch series (patches 1-4 of
4) and can find no obvious problems.  There do not appear to be any
regressions introduced by this patch series.  As noted, patch 2/4 does not
provide working backlight power control on an S7020 but it may well be that
this has never been functional on the S7020 (I do not make use of bl_power
myself).

I can add that immediately after loading the driver the value returned by a
read of bl_power is 0.  As noted above, setting to 1 makes no difference to
the backlight, neither does returning it to 0.  A value of 0 would normally
indicate that it's on I think, which means that the initial read of the
backlight power state does not appear to be working either.  As for the
other behaviour, this does not change if patch 2/4 is omitted.

Unfortunately I ran out of time over the weekend to cross check the
behaviour of bl_power on the S7020 with an unpatched kernel (as mentioned, I
don't utilise bl_power routinely myself and therefore can't recall whether
it has worked on my hardware in the past).  For completeness I will try to
look at this sometime this week.  However, given the patch content and the
observation that omitting patch 2/4 makes no difference to the S7020
behaviour I am satisfied that at least on S7020 this patch series does not
introduce any regressions and represents a worthwhile clean up of the
driver's code.

I am happy to see this series applied in its entirety (including patch 2/4).

Tested-by: Jonathan Woithe <jwoithe@...t42.net>
Reviewed-by: Jonathan Woithe <jwoithe@...t42.net>

Regards
  jonathan

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