Hello Zhangfei Gao, The patch 7bb587f4eef8: "dmaengine: add interface of dma_get_slave_channel" from Jun 28, 2013, leads to the following warning: "drivers/dma/dmaengine.c:531 dma_get_slave_channel() error: potential NULL dereference 'chan'." drivers/dma/dmaengine.c 516 struct dma_chan *dma_get_slave_channel(struct dma_chan *chan) 517 { 518 int err = -EBUSY; 519 520 /* lock against __dma_request_channel */ 521 mutex_lock(&dma_list_mutex); 522 523 if (chan->client_count == 0) 524 err = dma_chan_get(chan); 525 else 526 chan = NULL; ^^^^^^^^^^^ 527 528 mutex_unlock(&dma_list_mutex); 529 530 if (err) 531 pr_debug("%s: failed to get %s: (%d)\n", 532 __func__, dma_chan_name(chan), err); ^^^^ Dereferenced here. 533 534 return chan; regards, dan carpenter -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html