Re: dmaengine: add interface of dma_get_slave_channel

zhangfei
2013-08-15T01:29:18Z

On 13-08-15 03:51 AM, Dan Carpenter wrote:
> 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
>

Thanks Dan for point out.

I am sorry, make does not report such error here, is it config related.

Dear Vinod

Could I update this patch and resend to you?
Change to:
struct dma_chan *dma_get_slave_channel(struct dma_chan *chan)
{
int err = -EBUSY;

/* lock against __dma_request_channel */
mutex_lock(&dma_list_mutex);

if (chan->client_count = 0) {
err = dma_chan_get(chan);
if (err)
pr_debug("%s: failed to get %s: (%d)\n",
__func__, dma_chan_name(chan), err);
} else
chan = NULL;

mutex_unlock(&dma_list_mutex);

return chan;
}

Sorry for inconvenience.

Thanks