[PATCH] SPI: BCM2835: enable support of 3-wire mode

[pigpio]

Not sure what you guys are saying.

http://abyz.co.uk/rpi/pigpio/cif.html#spiOpen

On Fri, 2015-03-20 at 07:17 +0100, Martin Sperl wrote:
> > On 20.03.2015, at 06:12, Stephen Warren <swarren at wwwdotorg.org> wrote:
> > I can see how that tells the HW which direction to transfer data in
> > 3WIRE mode, but how does the HW know whether it's in 3WIRE mode or has
> > separate RX/TX lines?
> 
> The HW assumes with this flag that MISO (=RX) sits on the same physical
> line as MOSI (=TX). This flag essentially just changes directions of
> the TX GPIO pin from out to in and samples the level on the TX pin.
> 
> Without this patch what you would need to do to make such a device
> work is connecting RX with TX and that with the MIMO pin of the final
> device (maybe add a pullup). This flag is essentially just a shortcut.
> 
> Note that the SPI-framework does the testing so that either RX or TX
> can be set in SPI-3WIRE mode (not both).
> 
> Ciao,
> 	Martin
> 
> 
> 
> 
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