On Sun, Dec 16, 2012 at 5:03 PM, Geert Uytterhoeven [off-list ref]
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