spi: Fix zero length xfer bug

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This fixes a bug for messages containing both zero length and
unidirectional xfers.

The function spi_map_msg will allocate dummy tx and/or rx buffers
for use with unidirectional transfers when the hardware can only do
a bidirectional transfer.  That dummy buffer will be used in place
of a NULL buffer even when the xfer length is 0.

Then in the function __spi_map_msg, if he hardware can dma,
the zero length xfer will have spi_map_buf called on the dummy
buffer.

Eventually, __sg_alloc_table is called and returns -EINVAL
because nents == 0.

This fix prevents the error by not using the dummy buffer when
the xfer length is zero.

Signed-off-by: Chris Lesiak <chris.lesiak@licor.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

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Chris Lesiak 2019-03-07 20:39:00 +00:00 • committed by Mark Brown

parent 0e836c3bea

commit 5442dcaa0d

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drivers/spi/spi.c

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