From mboxrd@z Thu Jan 1 00:00:00 1970 From: Geert Uytterhoeven Subject: Re: [PATCH 8/9] parisc: Provide dma_mmap_coherent() and dma_get_sgtable() Date: Sun, 13 Jan 2013 15:52:25 +0100 Message-ID: References: <1358073890-3610-1-git-send-email-geert@linux-m68k.org> <1358073890-3610-8-git-send-email-geert@linux-m68k.org> <1358077001.3065.14.camel@dabdike.int.hansenpartnership.com> <1358084972.3065.18.camel@dabdike.int.hansenpartnership.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail-vb0-f53.google.com ([209.85.212.53]:50896 "EHLO mail-vb0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755106Ab3AMOw1 convert rfc822-to-8bit (ORCPT ); Sun, 13 Jan 2013 09:52:27 -0500 In-Reply-To: <1358084972.3065.18.camel@dabdike.int.hansenpartnership.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: James Bottomley Cc: linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, Marek Szyprowski , linux-parisc@vger.kernel.org On Sun, Jan 13, 2013 at 2:49 PM, James Bottomley wrote: > On Sun, 2013-01-13 at 14:12 +0100, Geert Uytterhoeven wrote: >> On Sun, Jan 13, 2013 at 12:36 PM, James Bottomley >> wrote: >> > On Sun, 2013-01-13 at 11:44 +0100, Geert Uytterhoeven wrote: >> >> parisc/allmodconfig: >> >> >> >> drivers/media/v4l2-core/videobuf2-dma-contig.c: In function =E2=80= =98vb2_dc_mmap=E2=80=99: >> >> drivers/media/v4l2-core/videobuf2-dma-contig.c:204: error: implic= it declaration of function =E2=80=98dma_mmap_coherent=E2=80=99 >> >> drivers/media/v4l2-core/videobuf2-dma-contig.c: In function =E2=80= =98vb2_dc_get_base_sgt=E2=80=99: >> >> drivers/media/v4l2-core/videobuf2-dma-contig.c:387: error: implic= it declaration of function =E2=80=98dma_get_sgtable=E2=80=99 >> >> >> >> For architectures using dma_map_ops, dma_mmap_coherent() and >> >> dma_get_sgtable() are provided in . >> >> >> >> Parisc does not use dma_map_ops, hence it should implement them a= s inline >> >> stubs using dma_common_mmap() and dma_common_get_sgtable(). >> >> >> >> Signed-off-by: Geert Uytterhoeven >> >> Cc: Marek Szyprowski >> >> Cc: linux-parisc@vger.kernel.org >> >> --- >> >> arch/parisc/include/asm/dma-mapping.h | 10 ++++++++++ >> >> 1 files changed, 10 insertions(+), 0 deletions(-) >> >> >> >> diff --git a/arch/parisc/include/asm/dma-mapping.h b/arch/parisc/= include/asm/dma-mapping.h >> >> index 467bbd5..1fac0bf 100644 >> >> --- a/arch/parisc/include/asm/dma-mapping.h >> >> +++ b/arch/parisc/include/asm/dma-mapping.h >> >> @@ -238,4 +238,14 @@ void * sba_get_iommu(struct parisc_device *d= ev); >> >> /* At the moment, we panic on error for IOMMU resource exaustion= */ >> >> #define dma_mapping_error(dev, x) 0 >> >> >> >> +/* drivers/base/dma-mapping.c */ >> >> +extern int dma_common_mmap(struct device *dev, struct vm_area_st= ruct *vma, >> >> + void *cpu_addr, dma_addr_t dma_addr, siz= e_t size); >> >> +extern int dma_common_get_sgtable(struct device *dev, struct sg_= table *sgt, >> >> + void *cpu_addr, dma_addr_t dma_ad= dr, >> >> + size_t size); >> >> + >> >> +#define dma_mmap_coherent(d, v, c, h, s) dma_common_mmap(d, v, c= , h, s) >> >> +#define dma_get_sgtable(d, t, v, h, s) dma_common_get_sgtable(d,= t, v, h, s) >> > >> > What is the documentation around these functions? The name sounds >> > suspiciously like you want a mapping of a buffer coherent between = kernel >> > and user space, which doesn't seem possible for us given the API. = We're >> > a VIPT architecture, so the only way we can do this is to have the >> > actual vma user space address be congruent with cpu_addr. How do = we do >> > that if the vma and kernel addresses are already fixed? >> >> I was already afraid of this when seeing the "coherent" in the namin= g... > > Afraid of what, that the interface won't actually work for VIPT or th= at > we need special functions? That it wouldn't work on parisc. > We won't be the only ones: MIPS at least will have this issue. MIPS uses , BUT has some ugly #ifdefery in sound/core/pcm_native.c:snd_pcm_lib_default_mmap(). BTW, does current ALSA mmap() work on parisc? > But I would like to clear up whether we can actually use this on PA o= r > not. > >> > In other words, either the interface is unusable by parisc, or the >> > common code definitely won't work for us. >> >> So you probably want a static inline function that returns -EINVAL f= or now? > > Yes, that should work (provided the consumers handle the return code > correctly). OK. Let's wait (for Marek's documentation) and see whether we can fix i= t for real in 3.8, or have to resort to -EINVAL. 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= =2E But when I'm talking to journalists I just say "programmer" or something li= ke that. -- Linus Torvalds