From c1c0dd2644d6bdd64f5d36528d801d14832f6394 Mon Sep 17 00:00:00 2001 From: Andrew Ruder Date: Thu, 24 Apr 2014 13:39:32 -0500 Subject: [PATCH] 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 Cc: Jean-Christophe PLAGNIOL-VILLARD Reviewed-by: Jagannadha Sutradharudu Teki --- 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 5d22351290..c969be31eb 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); -- 2.39.5