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 Cc: Jagan Teki jagannadh.teki@gmail.com --- Cleaned up errors/warnings from checkpatch.pl. I'm surprised they were flagged by the script since the actual ERRORs were all on lines I didn't change but were only included in the context.
scripts/checkpatch.pl 0001-spi-soft_spi-Support-NULL-din-dout-buffers.patch total: 0 errors, 0 warnings, 0 checks, 31 lines checked
drivers/spi/soft_spi.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/drivers/spi/soft_spi.c b/drivers/spi/soft_spi.c index 5d22351..c969be3 100644 --- a/drivers/spi/soft_spi.c +++ b/drivers/spi/soft_spi.c @@ -136,10 +136,14 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen, /* * Check if it is time to work on a new byte. */ - if((j % 8) == 0) { - tmpdout = *txd++; + if ((j % 8) == 0) { + if (txd) + tmpdout = *txd++; + else + tmpdout = 0; if(j != 0) { - *rxd++ = tmpdin; + if (rxd) + *rxd++ = tmpdin; } tmpdin = 0; } @@ -164,9 +168,11 @@ int spi_xfer(struct spi_slave *slave, unsigned int bitlen, * bits over to left-justify them. Then store the last byte * read in. */ - if((bitlen % 8) != 0) - tmpdin <<= 8 - (bitlen % 8); - *rxd++ = tmpdin; + if (rxd) { + if ((bitlen % 8) != 0) + tmpdin <<= 8 - (bitlen % 8); + *rxd++ = tmpdin; + }
if (flags & SPI_XFER_END) spi_cs_deactivate(slave);