GPIO operations, you should be able to leverage that for better
speed with a custom version of this driver; see the source code.
+config SPI_IMX
+ tristate "Freescale i.MX SPI controllers"
+ depends on ARCH_MXC
+ select SPI_BITBANG
+ help
+ This enables using the Freescale i.MX SPI controllers in master
+ mode.
+
config SPI_LM70_LLP
tristate "Parallel port adapter for LM70 eval board (DEVELOPMENT)"
depends on PARPORT && EXPERIMENTAL
help
SPI driver for SuperH SCI blocks.
+config SPI_STMP3XXX
+ tristate "Freescale STMP37xx/378x SPI/SSP controller"
+ depends on ARCH_STMP3XXX && SPI_MASTER
+ help
+ SPI driver for Freescale STMP37xx/378x SoC SSP interface
+
config SPI_TXX9
tristate "Toshiba TXx9 SPI controller"
depends on GENERIC_GPIO && CPU_TX49XX