spi: spidev_test: allow zero-length transfers

SPI drivers may in fact handle zero-length transfers. The behavior so
far was that such transfers would be executed but then result in the
"can't send spi message" error message because the spi_sync() call
returning 0 would be treated as an error while really it simply
indicates that zero bytes were successfully transferred in a message.

Don't treat a return value of zero as indication of an error.

Update hex_dump() to work with empty buffers now printing e.g.

  TX | __ ||

Now including a trailing newline.

Signed-off-by: Jonas Rebmann <jre@pengutronix.de>
Link: https://patch.msgid.link/20260924-spi-sun4i-spidev_test-v7-4-126e31a07fdc@pengutronix.de
Signed-off-by: Mark Brown <broonie@kernel.org>

0 files changed, 0 insertions, 0 deletions