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Commit cc211863 authored by Chris Lesiak's avatar Chris Lesiak Committed by Greg Kroah-Hartman
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spi: Fix zero length xfer bug



[ Upstream commit 5442dcaa0d90fc376bdfc179a018931a8f43dea4 ]

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: default avatarChris Lesiak <chris.lesiak@licor.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 8f7f333a
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