From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from exprod5og108.obsmtp.com (exprod5og108.obsmtp.com [64.18.0.186]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id C36BFB6F88 for ; Thu, 23 Jun 2011 22:13:48 +1000 (EST) Message-ID: <4E032DF2.20108@ge.com> Date: Thu, 23 Jun 2011 13:13:38 +0100 From: Martyn Welch MIME-Version: 1.0 To: Ralf Baechle 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> Content-Type: text/plain; charset=UTF-8 Cc: devel@driverdev.osuosl.org, linux-m32r-ja@ml.linux-m32r.org, linux-m32r@ml.linux-m32r.org, Paul Mundt , linux-sh@vger.kernel.org, Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Chris Metcalf , David Howells , linux-am33-list@redhat.com, Paul Mackerras , "H. Peter Anvin" , Thomas Gleixner , linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Ingo Molnar , x86@kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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