[PATCH] STAGING: Comedi: Build only on arches providing PAGE_KERNEL_NOCACHE
Martyn Welch
martyn.welch at ge.com
Thu Jun 23 11:53:36 UTC 2011
On 23/06/11 12:45, Ralf Baechle wrote:
> On architectures that don't define PAGE_KERNEL_NOCACHE, the Comedi driver turns
> into tragedy:
>
> CC [M] drivers/staging/comedi/drivers.o
> drivers/staging/comedi/drivers.c: In function ‘comedi_buf_alloc’:
> drivers/staging/comedi/drivers.c:505:41: error: ‘PAGE_KERNEL_NOCACHE’ 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. I 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 at linux-mips.org>
>
> drivers/staging/comedi/Kconfig | 1 +
> 1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/staging/comedi/Kconfig b/drivers/staging/comedi/Kconfig
> index 1502d80..bccdc12 100644
> --- a/drivers/staging/comedi/Kconfig
> +++ b/drivers/staging/comedi/Kconfig
> @@ -2,6 +2,7 @@ config COMEDI
> tristate "Data acquisition support (comedi)"
> default N
> depends on m
> + depends on BROKEN || FRV || M32R || MN10300 || SUPERH || TILE || X86
I'm sure I got comedi to compile on a 32-bit PPC board not that long ago. Has
something changed, or is this just not an exhaustive list?
> ---help---
> Enable support a wide range of data acquisition devices
> for Linux.
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