On Thu, 2011-06-23 at 13:02 +0100, Ralf Baechle wrote: > On Thu, Jun 23, 2011 at 12:53:36PM +0100, Martyn Welch wrote: > > > 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@xxxxxxxxxxxxxx> > > > > > > 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? It went away. There's a proper API (pgprot_noncached), but it depends what this is used for and it's likely to be broken anyways... what is that driver trying to map non-cached ? Cheers, Ben. > (Adding the PPC folks to cc.) > > A "git grep -w PAGE_KERNEL_NOCACHE arch/powerpc/" doesn't find anything so > I don't think the driver will build there. I don't have a PPC toolchain > to verify that. > > Ralf > -- > To unsubscribe from this list: send the line "unsubscribe linux-arch" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/devel
