David Hubbard <dmamf...@gmail.com> writes: > From: Cord Amfmgm <dmamf...@gmail.com> > > This changes the way the ohci emulation handles a Transfer Descriptor with > "Current Buffer Pointer" set to "Buffer End" + 1. > > The OHCI spec 4.3.1.2 Table 4-2 allows td.cbp to be one byte more than td.be > to signal the buffer has zero length. Currently qemu only accepts zero-length > Transfer Descriptors if the td.cbp is equal to 0, while actual OHCI hardware > accepts both cases.
Which version of the OHCI spec is this? I can't find it in the one copy Google throws up: http://download.microsoft.com/download/1/6/1/161ba512-40e2-4cc9-843a-923143f3456c/ohci_11.pdf > The qemu ohci emulation has a regression in ohci_service_td. Version 4.2 > and earlier matched the spec. (I haven't taken the time to bisect exactly > where the logic was changed.) > > With a tiny OS[1] that boots and executes a test, the issue can be seen: > > * OS that sends USB requests to a USB mass storage device > but sends td.cbp = td.be + 1 > * qemu 4.2 > * qemu HEAD (4e66a0854) > * Actual OHCI controller (hardware) <snip> -- Alex Bennée Virtualisation Tech Lead @ Linaro
