Commit 7e8edae3 authored Nov 05, 2019 by Takashi Iwai

ALSA: pcm: Handle special page mapping in the default mmap handler

When a driver needs to deal with a special buffer like a SG or a
vmalloc buffer, it has to set up the PCM page ops explicitly for the
corresponding helper function.  This is rather error-prone and many
people forgot or incorrectly used it.

For simplifying the call patterns and avoiding such a potential bug,
this patch enhances the PCM default mmap handler to check the
(pre-)allocated buffer type and handles the page gracefully depending
on the buffer type.  If the PCM page ops is given, the ops is still
used in a higher priority.  The new code path is only for the default
(NULL page ops) case.

Link: https://lore.kernel.org/r/20191105080138.1260-4-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent 1fe7f397

sound/core/pcm_native.c

+13 −1

Original line number	Diff line number	Diff line
		@@ -13,6 +13,7 @@
		#include <linux/pm_qos.h>
		#include <linux/io.h>
		#include <linux/dma-mapping.h>
		#include <linux/vmalloc.h>
		#include <sound/core.h>
		#include <sound/control.h>
		#include <sound/info.h>
		@@ -3335,8 +3336,19 @@ static inline struct page *
		snd_pcm_default_page_ops(struct snd_pcm_substream *substream, unsigned long ofs)
		{
		void *vaddr = substream->runtime->dma_area + ofs;

		switch (substream->dma_buffer.dev.type) {
		#ifdef CONFIG_SND_DMA_SGBUF
		case SNDRV_DMA_TYPE_DEV_SG:
		case SNDRV_DMA_TYPE_DEV_UC_SG:
		return snd_pcm_sgbuf_ops_page(substream, ofs);
		#endif /* CONFIG_SND_DMA_SGBUF */
		case SNDRV_DMA_TYPE_VMALLOC:
		return vmalloc_to_page(vaddr);
		default:
		return virt_to_page(vaddr);
		}
		}

		/*
		* fault callback for mmapping a RAM page

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