[U-Boot] [PATCH] usb: Early failure when the first descriptor read fails, one way or another

[Paul Kocialkowski <contact@paulk.fr>]

Le samedi 28 mars 2015 ? 18:26 +0100, Marek Vasut a ?crit :
> On Saturday, March 28, 2015 at 06:23:58 PM, Paul Kocialkowski wrote:
> > 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.
> > 
> > Signed-off-by: Paul Kocialkowski <contact@paulk.fr>
> > ---
> >  common/usb.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/common/usb.c b/common/usb.c
> > index 32e15cd..d1b3316 100644
> > --- a/common/usb.c
> > +++ b/common/usb.c
> > @@ -950,7 +950,7 @@ 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 1;
> >  	}
> > @@ -990,6 +990,9 @@ int usb_new_device(struct usb_device *dev)
> >  	case 64:
> >  		dev->maxpacketsize = PACKET_SIZE_64;
> >  		break;
> > +	default:
> > +		debug("usb_new_device: invalid max packet size\n");
> 
> Hi,
> 
> since this is an error, this should probably be a printf(). Also,
> to make the error message useful, it should state the invalid value
> due to which it failed.

Well, it is not unexpected behaviour in my use case (but I reckon it may
be generally speaking). Plugging an USB1 device on a controller that
doesn't support USB1 should normally fail, this is not some kind of
run-time error.

When this happens in Linux, it just fails (silently) and tries ohci
instead. I'm afraid there is no such mechanism in U-Boot, so the best we
can do is to treat the device as unsupported.

If you're not convinced by this, I can still make a v2 with printf, I
just don't think it's a necessity.

> Thanks!
> 
> > +		return 1;
> >  	}
> >  	dev->devnum = addr;
> 
> Best regards,
> Marek Vasut

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