linux-kernel - Re: crash on CONFIG_CFAG12864B=y in 2.6.20-rc3-mm1

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Date:	Thu, 1 Feb 2007 19:17:08 +0100
From:	"Miguel Ojeda" <maxextreme@...il.com>
To:	"Daniel Walker" <dwalker@...sta.com>
Cc:	akpm@...l.org, linux-kernel@...r.kernel.org
Subject: Re: crash on CONFIG_CFAG12864B=y in 2.6.20-rc3-mm1

On 2/1/07, Daniel Walker <dwalker@...sta.com> wrote:
> On Thu, 2007-02-01 at 18:39 +0100, Miguel Ojeda wrote:
> > On 2/1/07, Daniel Walker <dwalker@...sta.com> wrote:
> > > On Thu, 2007-02-01 at 18:13 +0100, Miguel Ojeda wrote:
> > >
> > > > >
> > > > >
> > > >
> > > > Well, I use the word "module" for both cases: When I modprobe
> > > > cfag12864b, if ks0108 fails, it doesn't get linked. So I thought the
> > > > same happen for built-in drivers (in other words, I didn't think
> > > > cfag12864b would be linked if ks0108 failed).
> > > >
> > > > So I'm waiting until someone tell me what is the right way to avoid
> > > > drivers like cfag12864b been inited if their dependencies failed.
> > > >
> > > > Anyway, thanks for discovering the bug (I wouldn't have discovered it
> > > > as my motherboard has parallel port ;).
> > >
> > > I have a parallel port, but I don't have the cfag12864b or ks0108 .. I
> >
> > In fact, you don't need the cfag12864b display, as the driver just
> > needs the parallel port for output (you can put some LEDs attached to
> > the parallel port to check the driver's operations and it will be
> > fine).
> >
> > BTW, why ks0108 didn't find the 888 parallel port? Haven't you got such
> number?
>
> You know I think your right, it may not have a parallel port.. It's so
> common I tend to take it for granted .
>

Sadly, parallel ports are dying :(

> > > think the simplest way to fix it would be to add a flag to ks0108 that
> > > signals successful initialization , then force cfag12864b to check for
> > > that ..
> >
> > Sure, that won't be a problem; however, maybe there is other better way
> (?).
>
> When you build the driver as a module the module loader will only load
> what is needed, and in order .. When the same driver is built-in the
> module_init() becomes a device_initcall() , and all device_initcall's
> get executed .. So you have to expect that cfag12864b drivers initcalls
> will run eventually and will need to be careful about it's
> initialization.

That is the real problem, indeed.

>
> Daniel
>
>

All right, if there is no other better way to avoid that, I will send
the patch soon.

Miguel

-- 
Miguel Ojeda
http://maxextreme.googlepages.com/index.htm
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