[U-Boot] [PATCH] usb: Early failure when the first descriptor read fails, one way or another
Paul Kocialkowski
contact at paulk.fr
Sat Mar 28 18:31:42 CET 2015
Le samedi 28 mars 2015 à 18:26 +0100, Marek Vasut a écrit :
> 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 at 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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