linux-kernel - Re: [PATCH 1/2] dmaengine: Cleanups for the slave <-> channel symlink support

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Message-ID: <CAMuHMdUdhqRU8NmHrcgKQpiVDsuFosWUykZs47HdF9RRCDv-KA@mail.gmail.com>
Date:   Thu, 30 Jan 2020 16:20:14 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     Vinod <vkoul@...nel.org>, dmaengine@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH 1/2] dmaengine: Cleanups for the slave <-> channel symlink support

Hi Peter,

On Thu, Jan 30, 2020 at 12:41 PM Peter Ujfalusi <peter.ujfalusi@...com> wrote:
> No need to use goto to jump over the
> return chan ? chan : ERR_PTR(-EPROBE_DEFER);
> We can just revert the check and return right there.
>
> Do not fail the channel request if the chan->name allocation fails, but
> print a warning about it.
>
> Change the dev_err to dev_warn if sysfs_create_link() fails as it is not
> fatal.
>
> Only attempt to remove the DMA_SLAVE_NAME symlink if it is created - or it
> was attempted to be created.
>
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>

Thanks for your patch!

> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -756,22 +756,24 @@ struct dma_chan *dma_request_chan(struct device *dev, const char *name)
>         }
>         mutex_unlock(&dma_list_mutex);
>
> -       if (!IS_ERR_OR_NULL(chan))
> -               goto found;
> -
> -       return chan ? chan : ERR_PTR(-EPROBE_DEFER);
> +       if (IS_ERR_OR_NULL(chan))
> +               return chan ? chan : ERR_PTR(-EPROBE_DEFER);
>
>  found:
> -       chan->slave = dev;
>         chan->name = kasprintf(GFP_KERNEL, "dma:%s", name);
> -       if (!chan->name)
> -               return ERR_PTR(-ENOMEM);
> +       if (!chan->name) {
> +               dev_warn(dev,
> +                        "Cannot allocate memory for slave symlink name\n");

No need to print a message, as the memory allocator core will have
screamed already.

> +               return chan;
> +       }
> +       chan->slave = dev;
>
>         if (sysfs_create_link(&chan->dev->device.kobj, &dev->kobj,
>                               DMA_SLAVE_NAME))
> -               dev_err(dev, "Cannot create DMA %s symlink\n", DMA_SLAVE_NAME);
> +               dev_warn(dev, "Cannot create DMA %s symlink\n", DMA_SLAVE_NAME);
>         if (sysfs_create_link(&dev->kobj, &chan->dev->device.kobj, chan->name))
> -               dev_err(dev, "Cannot create DMA %s symlink\n", chan->name);
> +               dev_warn(dev, "Cannot create DMA %s symlink\n", chan->name);
> +
>         return chan;
>  }
>  EXPORT_SYMBOL_GPL(dma_request_chan);

With the above fixed:
Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds