Re: [RFC] [PATCH] Fix b43 driver build for arm

From: Michael Buesch
Date: Sat Feb 23 2008 - 00:53:34 EST


On Saturday 23 February 2008, Gordon Farquharson wrote:
> On Fri, Feb 22, 2008 at 7:07 AM, Michael Buesch <mb@xxxxxxxxx> wrote:
> > On Friday 22 February 2008 05:24:32 Gordon Farquharson wrote:
> > > On Wed, Feb 20, 2008 at 12:37 PM, Sam Ravnborg <sam@xxxxxxxxxxxx> wrote:
> > >
> > > > Option 1) is the worst of the three as that can cost
> > > > of many hours bug-hunting.
> > > > Option 3) may seem optimal but I do not like to add more
> > > > complexity to this part of the build. And really I do not
> > > > know a reliable way to detech when we do cross builds anyway.
> > > >
> > > > Leaving us with option 2) that is simple, strighforward and harmless.
> > >
> > > Are you willing to sign off on and commit the patch?
> >
> > Only with a big fat comment added that the alignment is only needed
> > because of a broken sanity check in file2alias.c.
>
> How about this?
>
> ---
>
> Align the members of the SSB device structure to a 32 bit boundary so
> that the b43 driver can be built for arm using a cross compiler. This
> change is required so that the test in scripts/mod/file2alias.c that
> checks that the size of the device ID type against the size of the
> section in the object file succeeds (see
> http://lkml.org/lkml/2008/2/18/481 for discussion).
>
> Signed-off-by: Gordon Farquharson <gordonfarquharson@xxxxxxxxx>
>
> ---
>
> diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
> index 139d49d..93083ad 100644
> --- a/include/linux/mod_devicetable.h
> +++ b/include/linux/mod_devicetable.h
> @@ -351,7 +351,9 @@ struct sdio_device_id {
> struct ssb_device_id {
> __u16 vendor;
> __u16 coreid;
> - __u8 revision;
> + /* Explicit padding to support cross-compilation. */

A big fat comment is something like that:

/* Explicit padding to support a broken sanity check in file2alias.c.
* The check will compare the size of the structure in the kernel
* object file to the userspace the kernel is compiled on.
* This breaks on cross-compilation. This padding is a workaround
* for this. */

> + __u8 revision
> + __attribute__((aligned(sizeof(__u32))));
> };
> #define SSB_DEVICE(_vendor, _coreid, _revision) \
> { .vendor = _vendor, .coreid = _coreid, .revision = _revision, }
>


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