Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759356Ab1FWMDm (ORCPT ); Thu, 23 Jun 2011 08:03:42 -0400 Received: from h5.dl5rb.org.uk ([81.2.74.5]:47721 "EHLO duck.linux-mips.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753011Ab1FWMDk (ORCPT ); Thu, 23 Jun 2011 08:03:40 -0400 Date: Thu, 23 Jun 2011 13:02:35 +0100 From: Ralf Baechle To: Martyn Welch Cc: Greg Kroah-Hartman , devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org, David Howells , linux-m32r@ml.linux-m32r.org, linux-m32r-ja@ml.linux-m32r.org, linux-am33-list@redhat.com, Paul Mundt , linux-sh@vger.kernel.org, Chris Metcalf , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, linux-arch@vger.kernel.org, Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH] STAGING: Comedi: Build only on arches providing PAGE_KERNEL_NOCACHE Message-ID: <20110623120234.GA22524@linux-mips.org> References: <20110623114536.GA14011@linux-mips.org> <4E032940.5010205@ge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4E032940.5010205@ge.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2362 Lines: 51 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 > > > > 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? (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-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/