---- Original Message -----
From: "David Brownell" <david-b@xxxxxxxxxxx>
On Sunday 05 July 2009, Hemanth V wrote:
Do you see any major changes required to support
slave mode in the SPI core driver.
There *is* no such thing as a "SPI core driver"...
I was referring to
spi.c - SPI init/core code
We are able to
use the existing interface for slave mode also, but
some APIs/ Structures could be made generic.
Three things are obvious:
- A spi_master is not a slave side driver!
Yes a more generic or new structure would be good,
but the current one does work for slave mode also.
- Control model would need to be inverted
* Chip select would be one input,
not N outputs
* No clock rate controls at all
Conditional checks for slave/master mode have been added in
the driver where required.
* latency issues ... driver can't necessarily
respond quickly enough to guarantee no data
loss (FIFOs help)
We currently support both FIFO and DMA for
slave mode
* Can't re-use /dev/spidev*
* Request queue would have a very different role
- Some primitives are likely missing, for flow
control (when hardware has a READY handshake)
I think a few proposals for how to handle slave
side have been circulated.
So would it be possible to merge the slave support also for
now, and could be modified to support the new slave interface
as and when available.
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