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

[Paul Kocialkowski]

Le lundi 30 mars 2015 à 01:47 +0200, Marek Vasut a écrit :
> On Saturday, March 28, 2015 at 06:31:42 PM, Paul Kocialkowski wrote:
> > 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).
> 
> Why is this not unexpected in your case please ?

Because using an USB low speed device with an EHCI controller should
normally fail (that is, the first descriptor read returns 0 bytes), or
at least it does on the sunxi platforms. I thought there was no need to
report that as an error, but I changed my mind.

Since the end result is that the USB device won't work, I think it makes
sense to print an error.

> > If you're not convinced by this, I can still make a v2 with printf, I
> > just don't think it's a necessity.
> 
> Let me just understand what you're seeing a bit better first please .

At this point, v2 of this patch was sent as: usb: Early failure when the
first descriptor read fails or is invalid

Let me know if you need some more context on this.

-- 
Paul Kocialkowski, Replicant developer

Replicant is a fully free Android distribution running on several
devices, a free software mobile operating system putting the emphasis on
freedom and privacy/security.

Website: http://www.replicant.us/
Blog: http://blog.replicant.us/
Wiki/tracker/forums: http://redmine.replicant.us/

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