| Message ID | 20220625142138.19363-1-mkfssion@mkfssion.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4,1/2] hw: canokey: Remove HS support as not compliant to the spec | expand |
On Sat, Jun 25, 2022 at 10:21:37PM +0800, MkfsSion wrote: > Canokey core currently using 16 bytes as maximum packet size for > control endpoint, but to run the device in high-speed a 64 bytes > maximum packet size is required according to USB 2.0 specification. > Since we don't acutally need to run the device in high-speed, simply > don't assign high member in USBDesc. > > When canokey-qemu is used with xhci, xhci would drive canokey > in high speed mode, since the bcdUSB in canokey-core is 2.1, > yet canokey-core set bMaxPacketSize0 to be 16, this is out > of the spec as the spec said that ``The allowable maximum > control transfer data payload sizes...for high-speed devices, > it is 64 bytes''. > > In this case, usb device validation in Windows 10 LTSC 2021 > as the guest would fail. It would complain > USB\DEVICE_DESCRIPTOR_VALIDATION_FAILURE. > > Note that bcdUSB only identifies the spec version the device > complies, but it has no indication of its speed. So it is > allowed for the device to run in FS but comply the 2.1 spec. > > To solve the issue we decided to just drop the high > speed support. This only affects usb-ehci as usb-ehci would > complain speed mismatch when FS device is attached to a HS port. > That's why the .high member was initialized in the first place. > Meanwhile, xhci is not affected as it works well with FS device. > Since everyone is now using xhci, it does no harm to most users. > > Suggested-by: Hongren (Zenithal) Zheng <i@zenithal.me> > Signed-off-by: YuanYang Meng <mkfssion@mkfssion.com> > --- > hw/usb/canokey.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/hw/usb/canokey.c b/hw/usb/canokey.c > index 4a08b1cbd7..6a7ab965a5 100644 > --- a/hw/usb/canokey.c > +++ b/hw/usb/canokey.c > @@ -56,7 +56,6 @@ static const USBDesc desc_canokey = { > .iSerialNumber = STR_SERIALNUMBER, > }, > .full = &desc_device_canokey, > - .high = &desc_device_canokey, > .str = desc_strings, > }; > > -- > 2.36.1 > Reviewed-by: Hongren (Zenithal) Zheng <i@zenithal.me> kraxel could you please pick this patch and queue this up for PULL, thanks!
diff --git a/hw/usb/canokey.c b/hw/usb/canokey.c index 4a08b1cbd7..6a7ab965a5 100644 --- a/hw/usb/canokey.c +++ b/hw/usb/canokey.c @@ -56,7 +56,6 @@ static const USBDesc desc_canokey = { .iSerialNumber = STR_SERIALNUMBER, }, .full = &desc_device_canokey, - .high = &desc_device_canokey, .str = desc_strings, };
Canokey core currently using 16 bytes as maximum packet size for control endpoint, but to run the device in high-speed a 64 bytes maximum packet size is required according to USB 2.0 specification. Since we don't acutally need to run the device in high-speed, simply don't assign high member in USBDesc. When canokey-qemu is used with xhci, xhci would drive canokey in high speed mode, since the bcdUSB in canokey-core is 2.1, yet canokey-core set bMaxPacketSize0 to be 16, this is out of the spec as the spec said that ``The allowable maximum control transfer data payload sizes...for high-speed devices, it is 64 bytes''. In this case, usb device validation in Windows 10 LTSC 2021 as the guest would fail. It would complain USB\DEVICE_DESCRIPTOR_VALIDATION_FAILURE. Note that bcdUSB only identifies the spec version the device complies, but it has no indication of its speed. So it is allowed for the device to run in FS but comply the 2.1 spec. To solve the issue we decided to just drop the high speed support. This only affects usb-ehci as usb-ehci would complain speed mismatch when FS device is attached to a HS port. That's why the .high member was initialized in the first place. Meanwhile, xhci is not affected as it works well with FS device. Since everyone is now using xhci, it does no harm to most users. Suggested-by: Hongren (Zenithal) Zheng <i@zenithal.me> Signed-off-by: YuanYang Meng <mkfssion@mkfssion.com> --- hw/usb/canokey.c | 1 - 1 file changed, 1 deletion(-)