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Subject[PATCH/RFC 0/4] Re: dma_mmap_coherent / ARCH_HAS_DMA_MMAP_COHERENT
Date
On Sun, Dec 16, 2012 at 5:03 PM, Geert Uytterhoeven <geert@linux-m68k.org>
wrote:
> drivers/media/v4l2-core/videobuf2-dma-contig.c: In function ‘vb2_dc_mmap’:
> drivers/media/v4l2-core/videobuf2-dma-contig.c:204: error: implicit declaration of function ‘dma_mmap_coherent’
> drivers/media/v4l2-core/videobuf2-dma-contig.c: In function ‘vb2_dc_get_base_sgt’:
> drivers/media/v4l2-core/videobuf2-dma-contig.c:387: error: implicit declaration of function ‘dma_get_sgtable’
> make[6]: *** [drivers/media/v4l2-core/videobuf2-dma-contig.o] Error 1
> make[6]: Target `__build' not remade because of errors.
> make[5]: *** [drivers/media/v4l2-core] Error 2
>
> Both dma_mmap_coherent() and dma_get_sgtable() are defined in
> include/asm-generic/dma-mapping-common.h only, which is included by
> <asm/dma-mapping.h> on alpha, arm, arm64, hexagon, ia64, microblaze, mips,
> openrisc, powerpc, s390, sh, sparc, tile, unicore32, x86.
> Should the remaining architectures include this, too?
> Should it be moved to <linux/dma-mapping.h>?

I came up with an RFC-solution for this in [PATCH/RFC 3/4]
("avr32/bfin/c6x/cris/frv/m68k/mn10300/parisc/xtensa: Add dummy get_dma_ops()")
and [PATCH/RFC 4/4] ("common: dma-mapping: Move dma_common_*() to
<linux/dma-mapping.h>") of this series.

> Furthermore, there's ARCH_HAS_DMA_MMAP_COHERENT, which is defined
> by powerpc only:
> arch/powerpc/include/asm/dma-mapping.h:#define ARCH_HAS_DMA_MMAP_COHERENT
>
> and handled in some fishy way in sound/core/pcm_native.c:
>
> #ifndef ARCH_HAS_DMA_MMAP_COHERENT
> /* This should be defined / handled globally! */
> #ifdef CONFIG_ARM
> #define ARCH_HAS_DMA_MMAP_COHERENT
> #endif
> #endif
>
> /*
> * mmap the DMA buffer on RAM
> */
> int snd_pcm_lib_default_mmap(struct snd_pcm_substream *substream,
> struct vm_area_struct *area)
> {
> area->vm_flags |= VM_DONTEXPAND | VM_DONTDUMP;
> #ifdef ARCH_HAS_DMA_MMAP_COHERENT
> if (!substream->ops->page &&
> substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV)
> return dma_mmap_coherent(substream->dma_buffer.dev.dev,
> area,
> substream->runtime->dma_area,
> substream->runtime->dma_addr,
> area->vm_end - area->vm_start);
> #elif defined(CONFIG_MIPS) && defined(CONFIG_DMA_NONCOHERENT)
> if (substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV &&
> !plat_device_is_coherent(substream->dma_buffer.dev.dev))
> area->vm_page_prot = pgprot_noncached(area->vm_page_prot);
> #endif /* ARCH_HAS_DMA_MMAP_COHERENT */
> /* mmap with fault handler */
> area->vm_ops = &snd_pcm_vm_ops_data_fault;
> return 0;
> }
> EXPORT_SYMBOL_GPL(snd_pcm_lib_default_mmap);
>
> What's up here?

Probably an easy solution here is to kill ARCH_HAS_DMA_MMAP_COHERENT and
change the code to

#if defined(CONFIG_MIPS) && defined(CONFIG_DMA_NONCOHERENT)
if (substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV &&
!plat_device_is_coherent(substream->dma_buffer.dev.dev))
area->vm_page_prot = pgprot_noncached(area->vm_page_prot);
#else
if (!substream->ops->page &&
substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV)
return dma_mmap_coherent(substream->dma_buffer.dev.dev,
area,
substream->runtime->dma_area,
substream->runtime->dma_addr,
area->vm_end - area->vm_start);
#endif

but obviously I don't like the test for CONFIG_MIPS in generic code...

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

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