linux-kernel - Re: [PATCH 2/3] Input: ads7846 - fix up the pendown GPIO setup on Nokia 770

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CACRpkdYbtCODxWU8F48qGGBJoTL54R5Dj6iYLB6Z2MRwsDqYzw@mail.gmail.com>
Date: Tue, 14 Jan 2025 13:28:32 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: Aaro Koskinen <aaro.koskinen@....fi>, Helge Deller <deller@....de>, 
	Janusz Krzysztofik <jmkrzyszt@...il.com>, Tony Lindgren <tony@...mide.com>, linux-fbdev@...r.kernel.org, 
	linux-omap@...r.kernel.org, linux-input@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] Input: ads7846 - fix up the pendown GPIO setup on
 Nokia 770

On Mon, Jan 6, 2025 at 8:02 AM Dmitry Torokhov
<dmitry.torokhov@...il.com> wrote:
> On Thu, Jan 02, 2025 at 10:32:00PM +0100, Linus Walleij wrote:
> > On Thu, Jan 2, 2025 at 7:20 PM Aaro Koskinen <aaro.koskinen@....fi> wrote:
> >
> > > The GPIO is set up as an IRQ, so request it as non-exclusive. Otherwise the
> > > probe fails on Nokia 770 with:
> > >
> > >     ads7846 spi2.0: failed to request pendown GPIO
> > >     ads7846: probe of spi2.0 failed with error -16
> > >
> > > Also the polarity is wrong. Fix it.
> > >
> > > Fixes: 767d83361aaa ("Input: ads7846 - Convert to use software nodes")
> > > Signed-off-by: Aaro Koskinen <aaro.koskinen@....fi>
> >
> > Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
>
> Do we need to have this knowledge in the driver or can it be handled
> in GPIO subsystem or affected board support? Requesting a GPIO with "in"
> direction when it is also an interrupt source should be pretty common.

Hm I don't know exactly the question here but I try to answer
anyway :)

The patch makes the boardfile describe the polarity but the
boardfile (or device tree) cannot define directions, consumers
must specify this. The main reason is that actual users exist that
switch the direction of GPIOs at runtime so this has been designed
as a (runtime) consumer duty.

As for GPIOD_FLAGS_BIT_NONEXCLUSIVE, this enables the
GPIO subsystem to read the GPIO while the irqchip subsystem
can also handle the same GPIO line as an interrupt source, so
it's not exclusive to either subsystem.

Yours,
Linus Walleij