ALSA: core: Add continuous and vmalloc mmap ops

The mmap of continuous pages and vmalloc'ed pages are relatively
easily done in a shot with the existing helper functions.
Implement the mmap ops for those types, so that the mmap works without
relying on the page fault handling.

Link: https://lore.kernel.org/r/20210609162551.7842-6-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/memalloc.c

@@ -211,9 +211,19 @@ static void snd_dma_continuous_free(struct snd_dma_buffer *dmab)
 	free_pages_exact(dmab->area, dmab->bytes);
 }
 
+static int snd_dma_continuous_mmap(struct snd_dma_buffer *dmab,
+				   struct vm_area_struct *area)
+{
+	return remap_pfn_range(area, area->vm_start,
+			       dmab->addr >> PAGE_SHIFT,
+			       area->vm_end - area->vm_start,
+			       area->vm_page_prot);
+}
+
 static const struct snd_malloc_ops snd_dma_continuous_ops = {
 	.alloc = snd_dma_continuous_alloc,
 	.free = snd_dma_continuous_free,
+	.mmap = snd_dma_continuous_mmap,
 };
 
 /*
@@ -232,6 +242,12 @@ static void snd_dma_vmalloc_free(struct snd_dma_buffer *dmab)
 	vfree(dmab->area);
 }
 
+static int snd_dma_vmalloc_mmap(struct snd_dma_buffer *dmab,
+				struct vm_area_struct *area)
+{
+	return remap_vmalloc_range(area, dmab->area, 0);
+}
+
 static dma_addr_t snd_dma_vmalloc_get_addr(struct snd_dma_buffer *dmab,
 					   size_t offset)
 {
@@ -259,6 +275,7 @@ snd_dma_vmalloc_get_chunk_size(struct snd_dma_buffer *dmab,
 static const struct snd_malloc_ops snd_dma_vmalloc_ops = {
 	.alloc = snd_dma_vmalloc_alloc,
 	.free = snd_dma_vmalloc_free,
+	.mmap = snd_dma_vmalloc_mmap,
 	.get_addr = snd_dma_vmalloc_get_addr,
 	.get_page = snd_dma_vmalloc_get_page,
 	.get_chunk_size = snd_dma_vmalloc_get_chunk_size,