From 7dfffb9541bca80bbf8df1869564f9220ee150d2 Mon Sep 17 00:00:00 2001 From: Geert Uytterhoeven Date: Mon, 17 Aug 2015 15:08:55 +0200 Subject: [PATCH] dmaengine: Stricter legacy checking in dma_request_slave_channel_compat() dma_request_slave_channel_compat() is meant for drivers that support both DT and legacy platform device based probing: if DT channel DMA setup fails, it will fall back to platform data based DMA channel setup, using hardcoded DMA channel IDs and a filter function. However, if the DTS doesn't provide a "dmas" property for the device, the fallback is also used. If the legacy filter function is not hardcoded in the DMA slave driver, but comes from platform data, it will be NULL. Then dma_request_slave_channel_compat() will succeed incorrectly, and return a DMA channel, as a NULL legacy filter function actually means "all channels are OK", not "do not match". Later, when trying to use that DMA channel, it will fail with: rcar-dmac e6700000.dma-controller: rcar_dmac_prep_slave_sg: bad parameter: len=1, id=-22 To fix this, ensure that both the filter function and the DMA channel ID are not NULL before using the legacy fallback. Note that some DMA slave drivers can handle this failure, and will fall back to PIO. See also commit 056f6c87028544de ("dmaengine: shdma: Make dummy shdma_chan_filter() always return false"), which fixed the same issue for the case where shdma_chan_filter() is hardcoded in a DMA slave driver. Suggested-by: Arnd Bergmann Signed-off-by: Geert Uytterhoeven Signed-off-by: Vinod Koul --- include/linux/dmaengine.h | 3 +++ 1 file changed, 3 insertions(+) diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index 3a732ac95285..7ea9184eaa13 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -1237,6 +1237,9 @@ static inline struct dma_chan if (chan) return chan; + if (!fn || !fn_param) + return NULL; + return __dma_request_channel(mask, fn, fn_param); } #endif /* DMAENGINE_H */ -- GitLab