Hello M'boumba Cedric Madianga,
The patch 2b12c5580e0a: "dmaengine: stm32-dma: Fix residue
computation issue in cyclic mode" from Dec 13, 2016, leads to the
following static checker warning:
drivers/dma/stm32-dma.c:914 stm32_dma_tx_status()
error: we previously assumed 'chan->desc' could be null (see line 910)
drivers/dma/stm32-dma.c
868 static size_t stm32_dma_desc_residue(struct stm32_dma_chan *chan,
869 struct stm32_dma_desc *desc,
870 u32 next_sg)
871 {
872 u32 residue = 0;
873 int i;
874
875 /*
876 * In cyclic mode, for the last period, residue = remaining bytes from
877 * NDTR
878 */
879 if (chan->desc->cyclic && next_sg == 0)
Should this just be "desc->cyclic"?
880 return stm32_dma_get_remaining_bytes(chan);
881
882 /*
883 * For all other periods in cyclic mode, and in sg mode,
884 * residue = remaining bytes from NDTR + remaining periods/sg to be
885 * transferred
886 */
887 for (i = next_sg; i < desc->num_sgs; i++)
888 residue += desc->sg_req[i].len;
889 residue += stm32_dma_get_remaining_bytes(chan);
890
891 return residue;
892 }
[ snip ]
894 static enum dma_status stm32_dma_tx_status(struct dma_chan *c,
895 dma_cookie_t cookie,
896 struct dma_tx_state *state)
897 {
898 struct stm32_dma_chan *chan = to_stm32_dma_chan(c);
899 struct virt_dma_desc *vdesc;
900 enum dma_status status;
901 unsigned long flags;
902 u32 residue = 0;
903
904 status = dma_cookie_status(c, cookie, state);
905 if ((status == DMA_COMPLETE) || (!state))
906 return status;
907
908 spin_lock_irqsave(&chan->vchan.lock, flags);
909 vdesc = vchan_find_desc(&chan->vchan, cookie);
910 if (chan->desc && cookie == chan->desc->vdesc.tx.cookie)
^^^^^^^^^^
Check for NULL
911 residue = stm32_dma_desc_residue(chan, chan->desc,
912 chan->next_sg);
913 else if (vdesc)
914 residue = stm32_dma_desc_residue(chan,
^^^^
Unchecked dereference.
915 to_stm32_dma_desc(vdesc), 0);
916 dma_set_residue(state, residue);
917
918 spin_unlock_irqrestore(&chan->vchan.lock, flags);
919
920 return status;
921 }
922
regards,
dan carpenter
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