cvs commit: src/sys/dev/usb ehci.c ehcivar.h

[Ian Dowse]

iedowse     2006-05-24 03:04:11 UTC

  FreeBSD src repository

  Modified files:
    sys/dev/usb          ehci.c ehcivar.h 
  Log:
  Attempt to follow the procedure described in section 4.10 of the
  EHCI spec for linking in new qTDs into an asynchronous QH. This
  requires that there is a qTD marked as not active and not halted
  at the start of the QH's list, and the hardware will know to re-fetch
  the qTD on each pass rather than just looking at the overlay qTD:
  
    "The host controller must be able to advance the queue from the
    Fetch QH state in order to avoid all hardware/software race
    conditions. This simple mechanism allows software to simply link
    qTDs to the queue head and activate them, then the host controller
    will always find them if/when they are reachable."
  
  This is achieved by keeping an "inactivesqtd" entry on the QH list,
  and re-using it each time as the start of the next transfer, and
  allocating a new qTD to become the next inactivesqtd. Then a new
  transfer can be activated by just setting its "active" flag, which
  avoids all the previous messing with overlay qTD state in
  ehci_set_qh_qtd().
  
  Revision  Changes    Path
  1.45      +223 -94   src/sys/dev/usb/ehci.c
  1.14      +1 -0      src/sys/dev/usb/ehcivar.h