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Date: Tue, 25 Oct 2022 21:38:12 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Ricardo Ribalda <ribalda@...omium.org>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
linux-media@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] media: uvcvideo: Handle errors from calls to
usb_string
Hi Ricardo and Guenter,
Thank you for the patch.
On Tue, Oct 25, 2022 at 04:41:01PM +0200, Ricardo Ribalda wrote:
> From: Guenter Roeck <linux@...ck-us.net>
>
> On a Webcam from Quanta, we see the following error.
>
> usb 3-5: New USB device found, idVendor=0408, idProduct=30d2, bcdDevice= 0.03
> usb 3-5: New USB device strings: Mfr=3, Product=1, SerialNumber=2
> usb 3-5: Product: USB2.0 HD UVC WebCam
> usb 3-5: Manufacturer: Quanta
> usb 3-5: SerialNumber: 0x0001
> ...
> uvcvideo: Found UVC 1.10 device USB2.0 HD UVC WebCam (0408:30d2)
> uvcvideo: Failed to initialize entity for entity 5
> uvcvideo: Failed to register entities (-22).
>
> The Webcam reports an entity of type UVC_VC_EXTENSION_UNIT. It reports a
> string index of '7' associated with that entity. The attempt to read that
> string from the camera fails with error -32 (-EPIPE). usb_string() returns
> that error, but it is ignored. As result, the entity name is empty. This
> later causes v4l2_device_register_subdev() to return -EINVAL, and no
> entities are registered as result.
>
> While this appears to be a firmware problem with the camera, the kernel
> should still handle the situation gracefully. To do that, check the return
> value from usb_string(). If it reports an error, assign the entity's
> default name.
Sounds good. The perfect world in which firmwares could be fixed doesn't
exist.
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
>
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index 215fb483efb0..828c443faaa9 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -879,10 +879,8 @@ static int uvc_parse_vendor_control(struct uvc_device *dev,
> + n;
> memcpy(unit->extension.bmControls, &buffer[23+p], 2*n);
>
> - if (buffer[24+p+2*n] != 0)
> - usb_string(udev, buffer[24+p+2*n], unit->name,
> - sizeof(unit->name));
> - else
> + if (buffer[24+p+2*n] == 0 ||
> + usb_string(udev, buffer[24+p+2*n], unit->name, sizeof(unit->name)) < 0)
> sprintf(unit->name, "Extension %u", buffer[3]);
There's quite a bit of common code between all the cases. I'll submit a
patch that refactors it on top. There's thus no need for nitpicking
here, so
Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>
> list_add_tail(&unit->list, &dev->entities);
> @@ -1006,15 +1004,15 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
> memcpy(term->media.bmTransportModes, &buffer[10+n], p);
> }
>
> - if (buffer[7] != 0)
> - usb_string(udev, buffer[7], term->name,
> - sizeof(term->name));
> - else if (UVC_ENTITY_TYPE(term) == UVC_ITT_CAMERA)
> - sprintf(term->name, "Camera %u", buffer[3]);
> - else if (UVC_ENTITY_TYPE(term) == UVC_ITT_MEDIA_TRANSPORT_INPUT)
> - sprintf(term->name, "Media %u", buffer[3]);
> - else
> - sprintf(term->name, "Input %u", buffer[3]);
> + if (buffer[7] == 0 ||
> + usb_string(udev, buffer[7], term->name, sizeof(term->name)) < 0) {
> + if (UVC_ENTITY_TYPE(term) == UVC_ITT_CAMERA)
> + sprintf(term->name, "Camera %u", buffer[3]);
> + if (UVC_ENTITY_TYPE(term) == UVC_ITT_MEDIA_TRANSPORT_INPUT)
> + sprintf(term->name, "Media %u", buffer[3]);
> + else
> + sprintf(term->name, "Input %u", buffer[3]);
> + }
>
> list_add_tail(&term->list, &dev->entities);
> break;
> @@ -1047,10 +1045,8 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
>
> memcpy(term->baSourceID, &buffer[7], 1);
>
> - if (buffer[8] != 0)
> - usb_string(udev, buffer[8], term->name,
> - sizeof(term->name));
> - else
> + if (buffer[8] == 0 ||
> + usb_string(udev, buffer[8], term->name, sizeof(term->name)) < 0)
> sprintf(term->name, "Output %u", buffer[3]);
>
> list_add_tail(&term->list, &dev->entities);
> @@ -1072,10 +1068,8 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
>
> memcpy(unit->baSourceID, &buffer[5], p);
>
> - if (buffer[5+p] != 0)
> - usb_string(udev, buffer[5+p], unit->name,
> - sizeof(unit->name));
> - else
> + if (buffer[5+p] == 0 ||
> + usb_string(udev, buffer[5+p], unit->name, sizeof(unit->name)) < 0)
> sprintf(unit->name, "Selector %u", buffer[3]);
>
> list_add_tail(&unit->list, &dev->entities);
> @@ -1105,10 +1099,8 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
> if (dev->uvc_version >= 0x0110)
> unit->processing.bmVideoStandards = buffer[9+n];
>
> - if (buffer[8+n] != 0)
> - usb_string(udev, buffer[8+n], unit->name,
> - sizeof(unit->name));
> - else
> + if (buffer[8+n] == 0 ||
> + usb_string(udev, buffer[8+n], unit->name, sizeof(unit->name)) < 0)
> sprintf(unit->name, "Processing %u", buffer[3]);
>
> list_add_tail(&unit->list, &dev->entities);
> @@ -1136,10 +1128,8 @@ static int uvc_parse_standard_control(struct uvc_device *dev,
> unit->extension.bmControls = (u8 *)unit + sizeof(*unit);
> memcpy(unit->extension.bmControls, &buffer[23+p], n);
>
> - if (buffer[23+p+n] != 0)
> - usb_string(udev, buffer[23+p+n], unit->name,
> - sizeof(unit->name));
> - else
> + if (buffer[23+p+n] == 0 ||
> + usb_string(udev, buffer[23+p+n], unit->name, sizeof(unit->name)) < 0)
> sprintf(unit->name, "Extension %u", buffer[3]);
>
> list_add_tail(&unit->list, &dev->entities);
>
--
Regards,
Laurent Pinchart
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