Re: [PATCH RFC 0/5] *** SPI Slave mode support ***

[Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>]

Hello Jiada,

On Tue, Apr 25, 2017 at 12:56:23AM -0700, Jiada Wang wrote:
> the use case of
> "A (master) <=> B (slave)", "B (master) <=> C(slave)", do share MISO and
> MOSI lines,
> but there is no SS line between A and C. so for each SPI slave device, there
> is only one
> master device.

So you need a mutex to make A not use the bus while B communicates to C.
Otherwise you have two drivers on MOSI (A and B) and MISO (B and C).

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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