On Fri, 22 Feb 2008 14:36:53 -0500, Ned Forrester <[EMAIL PROTECTED]> wrote:
> Or are you and Atsushi talking about using spi_transfer.delay_usecs
> *with* a zero length transfer to effectively put a delay between the
> assertion of CS and the start of the first clock? If so, then I guess I
> miss
On Friday 22 February 2008, Ned Forrester wrote:
>
> So, what I think you said is that it would be better for pxa2xx_spi to
> silently ignore a zero-length message, passing it back with the rest of
> the message when all is complete, than to reject the message.
Yes. Remember that the reason to _
David Brownell wrote:
>> This would be OK. It would not be hard to fix pxa2xx_spi, for example,
>> to reject zero-length transfers in DMA mode, as long as it is acceptable
>> to reject the message in mid-message.
>
> Such "illegal message" rejection is best done early; "fail-fast".
> Mid-message
David Brownell wrote:
>> However, if the transfer is by DMA, note that the PXA255 and PXA270
>> Developer's Manuals have the following language regarding DMA lengths:
>>
>> LEN = 0 means zero bytes for descriptor-fetch transactions.
>> LEN = 0 is an invalid setting for no-descriptor-fetch
> > If the driver could not handle zero length transfer, then the driver
> > should reject it (just like unsupported transfer mode). Then the
> > behavior will be 'assert chip select and wait some time' or 'rejected
> > by the driver'.
>
> This would be OK. It would not be hard to fix pxa2xx_spi,
> >> David, do you think writing 0 bytes is a valid use of this API?
> >
> > Just a zero byte transfer ... no, though it depends what you mean
> > by "valid". (I'm not sure I'd expect all controller drivers to
> > reject such requests.) That has no effect on bits-on-the-wire,
> > and would make t
Quoth Atsushi Nemoto on Fri, 22 Feb 2008:
> On Fri, 22 Feb 2008 10:30:31 +0100, Marc Pignat <[EMAIL PROTECTED]> wrote:
> > > > David, do you think writing 0 bytes is a valid use of this API?
> > >
> > > Just a zero byte transfer ... no, though it depends what you mean
> > > by "valid". (I'm not s
David Brownell wrote:
>> David, do you think writing 0 bytes is a valid use of this API?
>
> Just a zero byte transfer ... no, though it depends what you mean
> by "valid". (I'm not sure I'd expect all controller drivers to
> reject such requests.) That has no effect on bits-on-the-wire,
> and wo
Atsushi Nemoto wrote:
> If the driver could not handle zero length transfer, then the driver
> should reject it (just like unsupported transfer mode). Then the
> behavior will be 'assert chip select and wait some time' or 'rejected
> by the driver'.
This would be OK. It would not be hard to fix
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