Re: deprecating fix->mmio_start and smem_start

[Geert Uytterhoeven <geert@linux-m68k.org>]

On Tue, 22 Apr 2008, Scott D. Davilla wrote:
> > On Tue, 22 Apr 2008, Scott D. Davilla wrote:
> > >  >On Tue, 22 Apr 2008, Benjamin Herrenschmidt wrote:
> > >  >>  We currently have a problem with those two members of struct
> > >  >>  fb_fix_screeninfo. The struct contains an "unsigned long" which means
> > >  >>  that:
> > >  >>
> > >  >>  - 64 bits kernels with 32 bits userspace can't pass a complete
> > > address
> > >  >>  - 32 bits machines with 64 bits resource_size_t can't pass a complete
> > >  >>  address
> > >  >>  - The structure isn't even properly padded to be 32/64 bits neutral
> > > in
> > >  >>  the first place.
> > >  >>
> > >  >  > We could define new versions of the struct with new get/set ioctls,
> > >  >>  or we could try to just deprecate those fields. What do you guys
> > > think ?
> > >  >
> > >  >As userspace doesn't really need those fields[1], we can easily
> > >  >deprecate them.
> > > 
> >  > kexec uses FBIOGET_FSCREENINFO and FBIOGET_VSCREENINFO. So if these
> >  > ioctls changes, it will possibly break kexec under vesafb and efifb.
> > 
> > Does kexec use the smem_start and mmio_start fields of
> > fb_fix_screeninfo?
> > 
> 
> In "kexec/arch/i386/x86-linux-setup.c", the routine "setup_linux_vesafb" uses
> smem_start, smem_len, and line_length.
> 
> This is used for vesafb and efifb framebuffer kernel boot param setup. This is
> required for PC hardware that do not contain a PC-BIOS and need the bootloader
> to setup the kernel video boot params.

OK, but the problem doesn't show up on x86-32 (no >32-bit physical
addresses yet), as x86_linux_param_header.lfb_base is uint32_t and there's no
way it's gonna change.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

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