On Fri, Apr 27, 2018 at 01:06:49PM +0300, Аладышев Константин wrote:
> Ok, I’ve finally got it working!
>
> As I said earlier, this keyboard has interrupt endpoint size = 32 bytes.
> SeaBIOS doesn’t allow it ("usb_kbd_setup" function checks for
> “(epdesc->wMaxPacketSize != 8)").
>
> But this fix is not enough, cause “ehci_poll_intr(struct usb_pipe *p, void
> *data)” use unsafe “memcpy_far” for data with size of “maxpacket”. So if
> maxpacket is 32, there will be 32 bytes copied. But “usb_check_key” function
> use “keyevent” structure address as data parameter for “ehci_poll_intr”
> function. And the size of this structure is only 8 bytes, so this will lead
> to memory corruption.
>
> If we look at "Device Class Definition for Human Interface Devices (HID)"
> specification (http://www.usb.org/developers/hidpage/HID1_11.pdf - Appendix
> B: Boot Interface Descriptors – page 59):
>
> “The HID Subclass 1 defines two descriptors for Boot Devices. Devices may
> append additional data to these boot reports, but the first 8 bytes of
> keyboard reports and the first 3 bytes of mouse reports must conform to the
> format defined by the Boot Report descriptor in order for the data to be
> correctly interpreted by the BIOS. The report may not exceed 8 bytes in
> length. The BIOS will ignore any extensions to reports. These descriptors
> describe reports that the BIOS expects to see.”
>
> This is a little ambiguous for me how “Devices may append additional data”
> but “The report may not exceed 8 bytes in length” (maybe I misunderstand “may
> not” in second sentence), but it looks like it is SeaBIOS responsibility to
> “ignore any extensions to reports”. What do you think?
It sounds like the device is out of spec. But, I don't think there's
any harm in supporting it.
I guess we could add a "datasize" parameter to usb_poll_intr() so that
only the requested amount of data is transferred.
-Kevin
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