568d0697f4
Support two new half-duplex SPI implementation restrictions, for links that talk to TX-only or RX-only devices. (Existing half-duplex flavors support both transfer directions, just not at the same time.) Move spi_async() into the spi.c core, and stop inlining it. Then make that function perform error checks and reject messages that demand more than the underlying controller can support. Based on a patch from Marek Szyprowski which did this only for the bitbanged GPIO driver. Cc: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>