Re: [PATCH] PCI: endpoint: IS_ERR() vs NULL bug in pci_epf_test_init_dma_chan()

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This patch changes for a tx dma channel. There is a similar problem for a
 rx one too. The code doesn't cause an error, but it is likely better to
change to just NULL checking.

2022年7月8日(金) 17:41 Dan Carpenter <dan.carpenter@xxxxxxxxxx>:

>
> The dma_request_channel() function doesn't return error pointers, it
> returns NULL.
>
> Fixes: fff86dfbbf82 ("PCI: endpoint: Enable DMA tests for endpoints with DMA capabilities")
> Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
> ---
> It's surprising and unfortunate that dma_request_channel() returns NULL
> while dma_request_chan_by_mask() returns error pointers.  These days
> static checkers will catch this so it's not as bad as it could be but
> still not ideal.
>
>  drivers/pci/endpoint/functions/pci-epf-test.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> index 34aac220dd4c..eed6638ab71d 100644
> --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> @@ -221,7 +221,7 @@ static int pci_epf_test_init_dma_chan(struct pci_epf_test *epf_test)
>         filter.dma_mask = BIT(DMA_MEM_TO_DEV);
>         dma_chan = dma_request_channel(mask, epf_dma_filter_fn, &filter);
>
> -       if (IS_ERR(dma_chan)) {
> +       if (!dma_chan) {
>                 dev_info(dev, "Failed to get private DMA tx channel. Falling back to generic one\n");
>                 goto fail_back_rx;
>         }
> --
> 2.35.1
>

Thanks,
Shunsuke.




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