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From: Takashi Iwai <tiwai@suse.de>
To: Christoph Hellwig <hch@lst.de>
Cc: iommu@lists.linux-foundation.org,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Takashi Iwai <tiwai@suse.de>, Robin Murphy <robin.murphy@arm.com>,
	Michal Simek <monstr@monstr.eu>,
	linux-arm-kernel@lists.infradead.org,
	linux-m68k@lists.linux-m68k.org, linux-parisc@vger.kernel.org,
	linux-sh@vger.kernel.org, linux-xtensa@linux-xtensa.org,
	linuxppc-dev@lists.ozlabs.org, x86@kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/7] ALSA: pcm: use dma_can_mmap() to check if a device supports dma_mmap_*
Date: Mon, 05 Aug 2019 11:22:03 +0200
Message-ID: <s5hzhkonf0k.wl-tiwai@suse.de> (raw)
In-Reply-To: <20190805091159.7826-5-hch@lst.de>

On Mon, 05 Aug 2019 11:11:56 +0200,
Christoph Hellwig wrote:
> 
> Replace the local hack with the dma_can_mmap helper to check if
> a given device supports mapping DMA allocations to userspace.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  sound/core/pcm_native.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index 703857aab00f..81c82c3ee8a2 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -220,12 +220,11 @@ static bool hw_support_mmap(struct snd_pcm_substream *substream)
>  {
>  	if (!(substream->runtime->hw.info & SNDRV_PCM_INFO_MMAP))
>  		return false;
> -	/* architecture supports dma_mmap_coherent()? */
> -#if defined(CONFIG_ARCH_NO_COHERENT_DMA_MMAP) || !defined(CONFIG_HAS_DMA)
> +	if (!dma_can_mmap(substream->dma_buffer.dev.dev))
> +		return false;
>  	if (!substream->ops->mmap &&
>  	    substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV)
>  		return false;
> -#endif

This won't work as expected, unfortunately.  It's a bit tricky check,
since the driver may have its own mmap implementation via
substream->ops->mmap, and the dma_buffer.dev.dev might point to
another object depending on the dma_buffer.dev.type.

So please replace with something like below:

--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -221,11 +221,10 @@ static bool hw_support_mmap(struct snd_pcm_substream *substream)
 	if (!(substream->runtime->hw.info & SNDRV_PCM_INFO_MMAP))
 		return false;
 	/* architecture supports dma_mmap_coherent()? */
-#if defined(CONFIG_ARCH_NO_COHERENT_DMA_MMAP) || !defined(CONFIG_HAS_DMA)
 	if (!substream->ops->mmap &&
-	    substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV)
+	    substream->dma_buffer.dev.type == SNDRV_DMA_TYPE_DEV &&
+	    !dma_can_mmap(substream->dma_buffer.dev.dev))
 		return false;
-#endif
 	return true;
 }
 
 

Thanks!

Takashi

  reply index

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-05  9:11 remove default fallbacks in dma_map_ops v2 Christoph Hellwig
2019-08-05  9:11 ` [PATCH 1/7] dma-mapping: move the dma_get_sgtable API comments from arm to common code Christoph Hellwig
2019-08-05  9:11 ` [PATCH 2/7] dma-mapping: explicitly wire up ->mmap and ->get_sgtable Christoph Hellwig
2019-08-05  9:11 ` [PATCH 3/7] dma-mapping: add a dma_can_mmap helper Christoph Hellwig
2019-08-05  9:11 ` [PATCH 4/7] ALSA: pcm: use dma_can_mmap() to check if a device supports dma_mmap_* Christoph Hellwig
2019-08-05  9:22   ` Takashi Iwai [this message]
2019-08-06  5:29     ` Christoph Hellwig
2019-08-06  6:00       ` Takashi Iwai
2019-08-05  9:11 ` [PATCH 5/7] m68knommu: add a pgprot_noncached stub Christoph Hellwig
2019-08-05  9:11 ` [PATCH 6/7] dma-mapping: remove ARCH_NO_COHERENT_DMA_MMAP Christoph Hellwig
2019-08-05  9:11 ` [PATCH 7/7] dma-mapping: provide a better default ->get_required_mask Christoph Hellwig

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