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    SubjectRe: [PATCH 2/2] DMAENGINE: generic channel status
    From
    On Thu, Mar 25, 2010 at 3:37 PM, Guennadi Liakhovetski
    <g.liakhovetski@gmx.de> wrote:
    > On Thu, 25 Mar 2010, Dan Williams wrote:
    >
    >> On Thu, Mar 25, 2010 at 1:58 PM, Guennadi Liakhovetski
    >> <g.liakhovetski@gmx.de> wrote:
    >> > On Thu, 25 Mar 2010, Linus Walleij wrote:
    >> >
    >> >> Convert the device_is_tx_complete() operation on the
    >> >> DMA engine to a generic device_tx_status()operation which
    >> >> can return three states, DMA_TX_RUNNING, DMA_TX_COMPLETE,
    >> >> DMA_TX_PAUSED.
    >> >>
    >> [..]
    >> > General: you converted all drivers to the new .device_tx_status() API, but
    >> > since they don't implement "residue," you left it uninitialised
    >> > everywhere. Wouldn't it be better to set it to 0 or total length,
    >> > depending on the complete / not complete status?
    >>
    >> Agree that it should not be uninitialized.  At the same time I do not
    >> want to require drivers that don't need it to go through the hassle of
    >> looking up a byte count, so perhaps all but the drivers that want this
    >> support can return a 'max byte count'??
    >
    > Why not assign one of the two - 0 if the transfer is complete (DMA_SUCCESS
    > status returned) or whatever max count otherwise? Except I do think this
    > might confuse some users - seeing a residue larger than the total transfer
    > length...
    >

    0 if complete makes sense and then the actual residue or all 0xf's to
    indicate "I don't support inflight residue reporting".

    --
    Dan
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