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authorAndrew Ruder <andrew.ruder@elecsyscorp.com>2014-04-24 13:39:32 -0500
committerJagannadha Sutradharudu Teki <jaganna@xilinx.com>2014-06-08 23:12:27 +0530
commitc1c0dd2644d6bdd64f5d36528d801d14832f6394 (patch)
treee00eeb8db9318ad294b18f9349a5fe60539d0975 /drivers/spi
parent04728086088e2dcc37ae0512a521246b21389838 (diff)
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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 <andrew.ruder@elecsyscorp.com> Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com> Reviewed-by: Jagannadha Sutradharudu Teki <jaganna@xilinx.com>
Diffstat (limited to 'drivers/spi')
-rw-r--r--drivers/spi/soft_spi.c18
1 files 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);