dmaengine: xilinx-vdma: add some sanity checks

The newly added xilinx_dma_prep_dma_cyclic function sometimes causes
a gcc warning about the use of the segment function in case
we never run into the inner loop of the function:

dma/xilinx/xilinx_vdma.c: In function 'xilinx_dma_prep_dma_cyclic':
dma/xilinx/xilinx_vdma.c:1808:23: error: 'segment' may be used uninitialized in this function [-Werror=maybe-uninitialized]
   segment->hw.control |= XILINX_DMA_BD_SOP;

This can only happen if the period len is zero (which would cause other
problems earlier), or if the buffer is shorter than a period. Neither
of them should ever happen, but by adding an explicit check for these two
cases, we can abort in a more controlled way, and the compiler is
able to see that we never use uninitialized data.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

diff --git a/drivers/dma/xilinx/xilinx_vdma.c b/drivers/dma/xilinx/xilinx_vdma.c
index 0af0cf4b5f2e4349f6d17e3c77c2300f0a2159eb..914268bc9990c838551c39dbdef523164aaca3db 100644 (file)
--- a/drivers/dma/xilinx/xilinx_vdma.c
+++ b/drivers/dma/xilinx/xilinx_vdma.c
@@ -1745,8 +1745,14 @@ static struct dma_async_tx_descriptor *xilinx_dma_prep_dma_cyclic(
        int i;
        u32 reg;
 
+       if (!period_len)
+               return NULL;
+
        num_periods = buf_len / period_len;
 
+       if (!num_periods)
+               return NULL;
+
        if (!is_slave_direction(direction))
                return NULL;