linux-kernel - Re: [PATCH] serdev: Fix detection of UART devices on Apple machines.

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Message-ID: <20200220063335.GA9421@innovation.ch>
Date:   Wed, 19 Feb 2020 22:33:35 -0800
From:   "Life is hard, and then you die" <ronald@...ovation.ch>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Rob Herring <robh@...nel.org>, Jiri Slaby <jslaby@...e.com>,
        Maximilian Luz <luzmaximilian@...il.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH] serdev: Fix detection of UART devices on Apple machines.


On Wed, Feb 19, 2020 at 12:15:19PM +0100, Greg Kroah-Hartman wrote:
> On Tue, Feb 11, 2020 at 11:47:23AM -0800, Ronald Tschalär wrote:
> > On Apple devices the _CRS method returns an empty resource template, and
> > the resource settings are instead provided by the _DSM method. But
> > commit 33364d63c75d6182fa369cea80315cf1bb0ee38e (serdev: Add ACPI
> > devices by ResourceSource field) changed the search for serdev devices
> > to require valid, non-empty resource template, thereby breaking Apple
> > devices and causing bluetooth devices to not be found.
> > 
> > This expands the check so that if we don't find a valid template, and
> > we're on an Apple machine, then just check for the device being an
> > immediate child of the controller and having a "baud" property.
> > 
> > Cc: <stable@...r.kernel.org> # 5.5
> > Signed-off-by: Ronald Tschalär <ronald@...ovation.ch>
> > ---
> >  drivers/tty/serdev/core.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
> > index ce5309d00280..0f64a10ba51f 100644
> > --- a/drivers/tty/serdev/core.c
> > +++ b/drivers/tty/serdev/core.c
> > @@ -18,6 +18,7 @@
> >  #include <linux/sched.h>
> >  #include <linux/serdev.h>
> >  #include <linux/slab.h>
> > +#include <linux/platform_data/x86/apple.h>
> 
> Why is this needed?  Just for the x86_apple_machine variable?

Yes.

> Why do we still have platform_data for new systems anymore?  Can't this
> go into a much more generic location?  Like as an inline function?

I'm not sure I follow you. What exactly would you like to see in the
function? The check that sets this variable? Note that this was
originally pulled out into a variable that is set once for performance
reasons - see commit 630b3aff8a51c.


  Cheers,

  Ronald