Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932472Ab1FWQBu (ORCPT ); Thu, 23 Jun 2011 12:01:50 -0400 Received: from mail-iw0-f174.google.com ([209.85.214.174]:40562 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759395Ab1FWQBs convert rfc822-to-8bit (ORCPT ); Thu, 23 Jun 2011 12:01:48 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=hYh0G40mMYk5Yb7SqYktKrOavGNtZF4owaAmMnuMccaaNK+IWz5bVTtjxEyiwEFehE 1dqPwpukw0jQq6txEBmZMxoy+sXIZMFfEfo5jnA0jyU7mey561gmdzEEVIpXA+h8+VaB M/m+6TqqPbKbQB5JDTdQqsA8bAi2E6fj7ZTVw= MIME-Version: 1.0 In-Reply-To: <20110623114536.GA14011@linux-mips.org> References: <20110623114536.GA14011@linux-mips.org> Date: Thu, 23 Jun 2011 18:01:47 +0200 X-Google-Sender-Auth: kcLn_n0i-1kAVj79QiMBhOsQu4k Message-ID: Subject: Re: [PATCH] STAGING: Comedi: Build only on arches providing PAGE_KERNEL_NOCACHE From: Geert Uytterhoeven 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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1977 Lines: 42 On Thu, Jun 23, 2011 at 13:45, 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 Acked-by: Geert Uytterhoeven If only to get m68k/allmodconfig going again (hmm, there's another staging driver preventing a green light). Gr{oetje,eeting}s,                         Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that.                                 -- Linus Torvalds -- 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/