linux-kernel - Re: [PATCH v2 0/4] fujitsu

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Date:   Mon, 6 Mar 2017 19:47:23 +0100
From:   Michał Kępień <kernel@...pniu.pl>
To:     Jonathan Woithe <jwoithe@...t42.net>
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
> > 
> > Some quick feedback.
> > 
> > On Mon, Mar 06, 2017 at 03:31:04PM +1030, Jonathan Woithe wrote:
> > > > > 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.
> > > > 
> > > > Have you tried setting bl_power to 4?  Because that is the value of
> > > > FB_BLANK_POWERDOWN, which is the value the patch is supposed to handle.
> > > 
> > > Oh no, I didn't try 4.  I should have.  I will try to squeeze in a test of
> > > this tonight (time is short but the test won't take a lot of time).
> > 
> > With an unpatched 4.5 kernel, writing 4 (as opposed to 1, which I stupidly
> > tried earlier) to bl_power caused the backlight to turn off.  Writing 0
> > turned it back on again.
> > 
> > With patches 1-4/4 applied, writing 4 to bl_power did *NOT* turn the
> > backlight off.
> > 
> > With patch 2 reverted, writing 4 to bl_power turned the backlight off. 
> > Writing 0 to bl_power turned it back on again.
> > 
> > This means that patch 2/4 seems to prevent bl_power from operating as
> > expected on the S7020 hardware.  Without this patch (but with all the others
> > in place) bl_power works.
> > 
> > I am unlikely to have any more time to investigate this further tonight. 
> > 
> > In light of the above findings, what would you like to do?
> 
> Thanks for testing, good that we caught this before the patch series was
> applied.  I think it is reasonable to skip applying this version of the
> series as at least patch 2/4 is faulty and breaks a working feature.
> 
> Moving on, though, as I do not have access to Fujitsu hardware on which
> this feature works, I was hoping you could help me verify whether my
> assumptions were reasonable in the first place.  
> 
> I attached a crude patch to this message.  I would like to understand
> how the underlying ACPI variables behave when the FEXT interface is
> used, so please apply this patch on top of dvhart/testing (i.e. without
> this series applied).  After compiling, please load the module with
> debugging enabled, then test backlight control once again by writing 4
> and then 0 to bl_power (this should work).  Then please send me all the
> messages spit out by the driver into dmesg.  This should shed some light
> on the matter.

Actually, scratch that.  I just ordered a banged up S7020 for €15 to
avoid pestering you with experimental patches and hopefully make the
whole driver cleanup process a bit smoother.

Darren, Andy, please ignore this whole series for now.  I will post v3
once I figure out how to clean things up without breaking working
features.

-- 
Best regards,
Michał Kępień