tree e00eeb8db9318ad294b18f9349a5fe60539d0975
parent 04728086088e2dcc37ae0512a521246b21389838
author Andrew Ruder <andrew.ruder@elecsyscorp.com> 1398364772 -0500
committer Jagannadha Sutradharudu Teki <jaganna@xilinx.com> 1402249347 +0530

spi: soft_spi: Support NULL din/dout buffers

This mirrors the conventions used in other SPI drivers (kirkwood,
davinci, atmel, et al) where the din/dout buffer can be NULL when the
received/transmitted data isn't important.  This reduces the need for
allocating additional buffers when write-only/read-only functionality is
needed.

In the din == NULL case, the received data is simply not stored.  In the
dout == NULL case, zeroes are transmitted.

Signed-off-by: Andrew Ruder <andrew.ruder@elecsyscorp.com>
Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Reviewed-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>