Re: [PATCH] STAGING: Comedi: Build only on arches providing PAGE_KERNEL_NOCACHE

[Geert Uytterhoeven]

On Thu, Jun 23, 2011 at 13:45, Ralf Baechle <ralf@xxxxxxxxxxxxxx> wrote:
> On architectures that don't define PAGE_KERNEL_NOCACHE, the Comedi driver turns
> into tragedy:
>
> ÂCC [M] Âdrivers/staging/comedi/drivers.o
> drivers/staging/comedi/drivers.c: In function âcomedi_buf_allocâ:
> drivers/staging/comedi/drivers.c:505:41: error: âPAGE_KERNEL_NOCACHEâ undeclared (first use in this function)
> drivers/staging/comedi/drivers.c:505:41: note: each undeclared identifier is rep orted only once for each function it appears in
> make[3]: *** [drivers/staging/comedi/drivers.o] Error 1
>
> Restrict the driver to only those architectures that define PAGE_KERNEL_NOCACHE.
>
> PAGE_KERNEL_NOCACHE is a kludge - some system architectures such as SGI IP27
> are even uable to offer uncached operation - at least in the way an unwitting
> driver might assume. ÂI haven't looked in details how the driver is using
> the area vmaped with PAGE_KERNEL_NOCACHE but maybe doing it XFS-style using
> cached memory and the flush_kernel_vmap_range / invalidate_kernel_vmap_range
> APIs in conjunction with the DMA API is a practical alternative.
>
> Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>

Acked-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>

If only to get m68k/allmodconfig going again (hmm, there's another
staging driver
preventing a green light).

Gr{oetje,eeting}s,

            Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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.
             Â Â -- Linus Torvalds
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