On Tue, 5 Oct 2010, James wrote:
> On 10/05/10 10:34, Alan Stern wrote:
> > On Mon, 4 Oct 2010, James wrote:
> >
> >> The patch works.
> > Here is a slightly revised version. This patch will print a warning
> > message in the system log to let you know that the device is out of
> > spec, but will allow it to be used anyway.
> >
> > If this version works okay with your device, I'll submit it for
> > inclusion in the -stable kernel series.
> >
> > Alan Stern
> >
> >
> >
> > Index: usb-2.6/drivers/usb/core/hub.c
> > ===================================================================
> > --- usb-2.6.orig/drivers/usb/core/hub.c
> > +++ usb-2.6/drivers/usb/core/hub.c
> > @@ -2882,13 +2882,16 @@ hub_port_init (struct usb_hub *hub, stru
> > else
> > i = udev->descriptor.bMaxPacketSize0;
> > if (le16_to_cpu(udev->ep0.desc.wMaxPacketSize) != i) {
> > - if (udev->speed != USB_SPEED_FULL ||
> > + if (udev->speed == USB_SPEED_LOW ||
> > !(i == 8 || i == 16 || i == 32 || i == 64)) {
> > - dev_err(&udev->dev, "ep0 maxpacket = %d\n", i);
> > + dev_err(&udev->dev, "Invalid ep0 maxpacket: %d\n", i);
> > retval = -EMSGSIZE;
> > goto fail;
> > }
> > - dev_dbg(&udev->dev, "ep0 maxpacket = %d\n", i);
> > + if (udev->speed == USB_SPEED_FULL)
> > + dev_dbg(&udev->dev, "ep0 maxpacket = %d\n", i);
> > + else
> > + dev_warn(&udev->dev, "Using ep0 maxpacket: %d\n", i);
> > udev->ep0.desc.wMaxPacketSize = cpu_to_le16(i);
> > usb_ep0_reinit(udev);
> > }
> >
> > --
> usb 1-2: new high speed USB device using ehci_hcd and address 7
> usb 1-2: Using ep0 maxpacket: 32
> usb 1-2: New USB device found, idVendor=1fdd, idProduct=0001
> usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
> scsi5 : usb-storage 1-2:1.0
> scsi 5:0:0:0: Direct-Access RCA VR5220 1.00 PQ: 0 ANSI: 2
> sd 5:0:0:0: [sdb] 999424 512-byte logical blocks: (511 MB/488 MiB)
> sd 5:0:0:0: [sdb] Write Protect is off
> sd 5:0:0:0: [sdb] Mode Sense: 00 00 00 00
> sd 5:0:0:0: [sdb] Assuming drive cache: write through
> sd 5:0:0:0: [sdb] Assuming drive cache: write through
> sdb:
> sd 5:0:0:0: [sdb] Assuming drive cache: write through
> sd 5:0:0:0: [sdb] Attached SCSI removable disk
>
> I'm wondering if the message should be more informative about it
> violating the USB Spec, like "Violating section 5.5.3 of the USB-2.0
> specification by using ep0 maxpacket: %d\n".
No, that's not necessary. We accept several other configuration values
that violate the spec; in each case there's a warning message but it's
not as detailed as you suggest.
> I think there no needs to be an 'if' to not have a message for devices
> in spec.
There _is_ such an "if". If the device is in spec then the patch gives
a debugging message instead of a warning. If the kernel was build
without CONFIG_USB_DEBUG then these debugging message never even get
issued.
Alan Stern
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