On 04/04/2015 07:12 AM, Paul Kocialkowski wrote:
> This may happen when using an USB1 device on a controller that only supports
> USB2 (e.g. EHCI). Reading the first descriptor will fail (read 0 byte), so we
> can abort the process at this point instead of failing later and wasting time.
FYI, this patch breaks USB keyboard (or perhaps any USB 1.x device)
support on the RPi.
> diff --git a/common/usb.c b/common/usb.c
> @@ -956,7 +956,7 @@ int usb_new_device(struct usb_device *dev)
> */
> #ifndef CONFIG_USB_XHCI
> err = usb_get_descriptor(dev, USB_DT_DEVICE, 0, desc, 64);
> - if (err < 0) {
> + if (err < sizeof(struct usb_device_descriptor)) {
> debug("usb_new_device: usb_get_descriptor() failed\n");
> return -EIO;
> }
The value returned here is 8 not 18 (the sizeof the descriptor), so the
code bails out with an error.
Given the description of what this patch is attempting to achieve,
shouldn't the replacement check be:
if (err <= 0) {
My guess for why the value 8 is returned is because the device's
maxpacket is 8, and the DWC2 driver only attempts to transfer 1 packet
because the requested transfer size is 64, and the default packet size
is 64, which means 1 packet. Note that DWC2 HW (perhaps unlike e.g.
EHCI) requires the driver to specify the number of packets transferred,
not a byte count. However, I haven't validated that yet. My device is a
USB 1.x FS keyboard.
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