Re: [PATCH 2/2] DMAENGINE: generic channel status

[Dan Williams <dan.j.williams@intel.com>]

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