diff options
| author |   Mark Brown <broonie@linaro.org> | 2014-01-10 17:09:53 +0000 |
|---|---|---|
| committer | Mark Brown <broonie@linaro.org> | 2014-01-13 10:13:28 +0000 |
| commit | d3fbd457013c0f6d96de461ce0a9cb1f8b73cd0b (patch) | |
| tree | 0e6cce807a503acdeac23e1267a4c2fb1c9585b6 /include/linux/spi | |
| parent | spi: core: Use list_first_entry to extract head of queue (diff) | |
| download | linux-dev-d3fbd457013c0f6d96de461ce0a9cb1f8b73cd0b.tar.xz linux-dev-d3fbd457013c0f6d96de461ce0a9cb1f8b73cd0b.zip | |
spi: Use bitfields for multiple data lines
Trent Piepho observed that since the current realistic maximum number of
data lines is four we can pack the spi_transfer struct more efficiently
if we use a bitfield for the number of bits, allowing the fields to fit
in a single byte along with cs_change.
If space becomes an issue further optimiation is possible by only using
the constants and packing the values chosen for them.
Reported-by: Trent Piepho <tpiepho@gmail.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
Diffstat (limited to 'include/linux/spi')
| -rw-r--r-- | include/linux/spi/spi.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index 27a882978c15..77b529e418d5 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -576,8 +576,8 @@ struct spi_transfer { dma_addr_t rx_dma; unsigned cs_change:1; - u8 tx_nbits; - u8 rx_nbits; + unsigned tx_nbits:3; + unsigned rx_nbits:3; #define SPI_NBITS_SINGLE 0x01 /* 1bit transfer */ #define SPI_NBITS_DUAL 0x02 /* 2bits transfer */ #define SPI_NBITS_QUAD 0x04 /* 4bits transfer */ |