Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759412Ab1FWMNr (ORCPT ); Thu, 23 Jun 2011 08:13:47 -0400 Received: from exprod5og104.obsmtp.com ([64.18.0.178]:59931 "EHLO exprod5og104.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757947Ab1FWMNp (ORCPT ); Thu, 23 Jun 2011 08:13:45 -0400 Message-ID: <4E032DF2.20108@ge.com> Date: Thu, 23 Jun 2011 13:13:38 +0100 From: Martyn Welch Organization: GE Intelligent Platforms User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.17) Gecko/20110424 Thunderbird/3.1.10 MIME-Version: 1.0 To: Ralf Baechle 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 References: <20110623114536.GA14011@linux-mips.org> <4E032940.5010205@ge.com> <20110623120234.GA22524@linux-mips.org> In-Reply-To: <20110623120234.GA22524@linux-mips.org> X-Enigmail-Version: 1.1.2 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-OriginalArrivalTime: 23 Jun 2011 12:11:17.0002 (UTC) FILETIME=[A766AEA0:01CC319E] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3494 Lines: 76 On 23/06/11 13:02, 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 >>> >>> 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. Ah, just found the tree looks like I had a little patch to make it seemingly work, though it will make it "not work" for most other archs at a guess (it may not even be right on PPC): diff --git a/drivers/staging/comedi/drivers.c b/drivers/staging/comedi/drivers.c index 44d6b62..263ad3d 100644 --- a/drivers/staging/comedi/drivers.c +++ b/drivers/staging/comedi/drivers.c @@ -505,7 +505,7 @@ int comedi_buf_alloc(struct comedi_device *dev, struct comedi_subdevice *s, } if (i == n_pages) { async->prealloc_buf = - vmap(pages, n_pages, VM_MAP, PAGE_KERNEL_NOCACHE); + vmap(pages, n_pages, VM_MAP, PAGE_KERNEL_NC); } vfree(pages); (Sorry for the wrapping) -- Martyn Welch (Principal Software Engineer) | Registered in England and GE Intelligent Platforms | Wales (3828642) at 100 T +44(0)127322748 | Barbirolli Square, Manchester, E martyn.welch@ge.com | M2 3AB VAT:GB 927559189 -- 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/