From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id E5538B6F9E for ; Thu, 23 Jun 2011 22:23:38 +1000 (EST) Subject: Re: [PATCH] STAGING: Comedi: Build only on arches providing PAGE_KERNEL_NOCACHE Mime-Version: 1.0 (Apple Message framework v1084) Content-Type: text/plain; charset=windows-1252 From: Kumar Gala In-Reply-To: <20110623120234.GA22524@linux-mips.org> Date: Thu, 23 Jun 2011 07:10:29 -0500 Message-Id: <8B77EED3-D197-4AB9-9594-278DB7002D6D@kernel.crashing.org> References: <20110623114536.GA14011@linux-mips.org> <4E032940.5010205@ge.com> <20110623120234.GA22524@linux-mips.org> To: Ralf Baechle Cc: devel@driverdev.osuosl.org, David Howells , linux-m32r@ml.linux-m32r.org, Paul Mundt , linux-sh@vger.kernel.org, Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Chris Metcalf , Martyn Welch , linux-am33-list@redhat.com, Paul Mackerras , linux-m32r-ja@ml.linux-m32r.org, "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 Jun 23, 2011, at 7:02 AM, Ralf Baechle wrote: > On Thu, Jun 23, 2011 at 12:53:36PM +0100, Martyn Welch wrote: >=20 >> On 23/06/11 12:45, Ralf Baechle wrote: >>> On architectures that don't define PAGE_KERNEL_NOCACHE, the Comedi = driver turns >>> into tragedy: >>>=20 >>> CC [M] drivers/staging/comedi/drivers.o >>> drivers/staging/comedi/drivers.c: In function =91comedi_buf_alloc=92: >>> drivers/staging/comedi/drivers.c:505:41: error: = =91PAGE_KERNEL_NOCACHE=92 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 >>>=20 >>> Restrict the driver to only those architectures that define = PAGE_KERNEL_NOCACHE. >>>=20 >>> 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. >>>=20 >>> Signed-off-by: Ralf Baechle >>>=20 >>> drivers/staging/comedi/Kconfig | 1 + >>> 1 files changed, 1 insertions(+), 0 deletions(-) >>>=20 >>> 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 >>=20 >> 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? >=20 > (Adding the PPC folks to cc.) >=20 > 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. I can verify it fails on PPC as well: drivers/staging/comedi/drivers.c: In function 'comedi_buf_alloc': drivers/staging/comedi/drivers.c:505:37: error: 'PAGE_KERNEL_NOCACHE' = undeclared (first use in this function) drivers/staging/comedi/drivers.c:505:37: note: each undeclared = identifier is reported only once for each function it appears in However, we do have a #define for PAGE_KERNEL_NC. - k=