Several drivers reuse mapped scatterlists, and modify sg_dma_len(sg) to
match the actual number of bytes they want to transfer.
Hence during driver shutdown, dma_unmap_sg() is called with a scatterlist
that has modified lengths, compared to the original passed to dma_map_sg().
If CONFIG_DMA_API_DEBUG=y, this causes warnings like:
WARNING: CPU: 0 PID: 20 at lib/dma-debug.c:1103 check_unmap+0x24c/0x85c()
rcar-dmac e6700000.dma-controller: DMA-API: device driver frees
DMA memory with different size [device address=0x000000006e15f000]
[map size=4096 bytes] [unmap size=3 bytes]
The warning can be silenced by restoring the original sg_dma_len() just before
calling dma_unmap_sg(), but it looks like no driver actually does that.
Is it allowed to modify sg_dma_len(sg)?
Is it OK to restore the original sg_dma_len()?
Thanks for your answers!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
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
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