Hello Takashi Iwai,

The patch 925ca893b4a6: "ALSA: memalloc: Add fallback SG-buffer allocations for x86" from Apr 13, 2022, leads to the following Smatch static checker warning:

sound/core/memalloc.c:732 snd_dma_sg_fallback_alloc() error: 'p' came from dma_alloc_coherent() so we can't do virt_to_phys()

sound/core/memalloc.c 708 static void *snd_dma_sg_fallback_alloc(struct snd_dma_buffer *dmab, size_t size) 709 { 710 struct snd_dma_sg_fallback *sgbuf; 711 struct page **pages; 712 size_t i, count; 713 void *p; 714 715 sgbuf = kzalloc(sizeof(*sgbuf), GFP_KERNEL); 716 if (!sgbuf) 717 return NULL; 718 count = PAGE_ALIGN(size) >> PAGE_SHIFT; 719 pages = kvcalloc(count, sizeof(*pages), GFP_KERNEL); 720 if (!pages) 721 goto error; 722 sgbuf->pages = pages; 723 sgbuf->addrs = kvcalloc(count, sizeof(*sgbuf->addrs), GFP_KERNEL); 724 if (!sgbuf->addrs) 725 goto error; 726 727 for (i = 0; i < count; sgbuf->count++, i++) { 728 p = dma_alloc_coherent(dmab->dev.dev, PAGE_SIZE, 729 &sgbuf->addrs[i], DEFAULT_GFP); 730 if (!p) 731 goto error; --> 732 sgbuf->pages[i] = virt_to_page(p);

The warning is a bit useless. It's complaining about __phys_addr() and not virt_to_phys(). I don't really understand the rules here, it might be legal in certain contexts.

733 } 734 735 if (dmab->dev.type == SNDRV_DMA_TYPE_DEV_WC_SG_FALLBACK) 736 set_pages_array_wc(pages, count); 737 p = vmap(pages, count, VM_MAP, PAGE_KERNEL); 738 if (!p) 739 goto error; 740 dmab->private_data = sgbuf; 741 return p; 742

regards, dan carpenter