linux-kernel - Re: [PATCH] media: pwc: Fix the URB buffer allocation

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Date:   Fri, 22 Jan 2021 09:57:13 +0100
From:   Robert Foss <robert.foss@...aro.org>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     Hans Verkuil <hverkuil@...all.nl>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media <linux-media@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: pwc: Fix the URB buffer allocation

Thanks for the patch, it all looks good to me.

Feel free to add my r-b:
Reviewed-by: Robert Foss <robert.foss@...aro.org>

On Thu, 21 Jan 2021 at 21:34, Takashi Iwai <tiwai@...e.de> wrote:
>
> The URB buffer allocation of pwc driver involves with the
> dma_map_single(), and it needs to pass the right device.  Currently it
> passes usb_device.dev, but it's no real device that manages the DMA.
> Since the passed device has no DMA mask set up, now the pwc driver
> hits the WARN_ON_ONCE() check in dma_map_page_attrs() (that was
> introduced in 5.10), resulting in an error at URB allocations.
> Eventually this ended up with the black output.
>
> This patch fixes the bug by passing the proper device, the bus
> controller, to make the URB allocation and map working again.
>
> BugLink: https://bugzilla.suse.com/show_bug.cgi?id=1181133
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai@...e.de>
> ---
>  drivers/media/usb/pwc/pwc-if.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/usb/pwc/pwc-if.c b/drivers/media/usb/pwc/pwc-if.c
> index 61869636ec61..d771160bb168 100644
> --- a/drivers/media/usb/pwc/pwc-if.c
> +++ b/drivers/media/usb/pwc/pwc-if.c
> @@ -461,7 +461,7 @@ static int pwc_isoc_init(struct pwc_device *pdev)
>                 urb->pipe = usb_rcvisocpipe(udev, pdev->vendpoint);
>                 urb->transfer_flags = URB_ISO_ASAP | URB_NO_TRANSFER_DMA_MAP;
>                 urb->transfer_buffer_length = ISO_BUFFER_SIZE;
> -               urb->transfer_buffer = pwc_alloc_urb_buffer(&udev->dev,
> +               urb->transfer_buffer = pwc_alloc_urb_buffer(udev->bus->controller,
>                                                             urb->transfer_buffer_length,
>                                                             &urb->transfer_dma);
>                 if (urb->transfer_buffer == NULL) {
> @@ -524,7 +524,7 @@ static void pwc_iso_free(struct pwc_device *pdev)
>                 if (urb) {
>                         PWC_DEBUG_MEMORY("Freeing URB\n");
>                         if (urb->transfer_buffer)
> -                               pwc_free_urb_buffer(&urb->dev->dev,
> +                               pwc_free_urb_buffer(urb->dev->bus->controller,
>                                                     urb->transfer_buffer_length,
>                                                     urb->transfer_buffer,
>                                                     urb->transfer_dma);
> --
> 2.26.2
>