Re: correct use of bus_dmamap_sync

From: Dinesh Nair (dinesh_at_alphaque.com)
Date: 10/27/05

  • Next message: Dinesh Nair: "locking in a device driver (was: use of bus_dmamap_sync)" 
    Date: Thu, 27 Oct 2005 13:47:59 +0800
To: Scott Long <scottl@samsco.org>

    On 10/27/05 04:16 Scott Long said the following:
    >>> an example would be using (BUS_DMASYNC_POSTREAD|BUS_DMASYNC_PREWRITE)
    >>> which
    >>> would be 0x03 in freebsd 4.x and 0x06 in freebsd 5.x. the gotcha is that
    >>> 0x03 in freebsd 4.x is BUS_DMASYNC_POSTWRITE. so therefore,
    >>> BUS_DMASYNC_POSTREAD|BUS_DMASYNC_PREWRITE will be
    >>> BUS_DMASYNC_POSTWRITE in
    >>> 4.x which in the syscall is actually a no op.
    >>
    >> Yes, that is fugly. Just don't use the | versions for now I would guess.
    >
    > Trying to maintain source compatibility between 4.x and 5.x/6.x will
    > make you encounter a whole lot more problems than just this.

    could you elaborate on what busdma related problems there'd be, between 4.x
    and 5.x/6.x ? do, for example, the inner workings of the bus_dma* syscalls
    work the same on both ? 

    -- 
Regards,                           /\_/\   "All dogs go to heaven."
dinesh@alphaque.com                (0 0)    http://www.alphaque.com/
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