2006-06-14 00:22:50 +00:00
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/*
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* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 of the
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* License, or any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include <stddef.h>
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#include <stdint.h>
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#include <string.h>
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2006-12-04 15:36:51 +00:00
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#include <byteswap.h>
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2006-06-14 00:22:50 +00:00
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#include <errno.h>
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#include <assert.h>
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#include <timer.h>
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#include <gpxe/bitbash.h>
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2006-12-04 15:36:51 +00:00
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#include <gpxe/spi_bit.h>
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2006-06-14 00:22:50 +00:00
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/** @file
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*
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* SPI bit-bashing interface
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*
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*/
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/** Delay between SCLK changes and around SS changes */
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2006-12-04 15:36:51 +00:00
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static void spi_bit_delay ( void ) {
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udelay ( SPI_BIT_UDELAY );
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2006-06-14 00:22:50 +00:00
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}
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2006-12-04 15:36:51 +00:00
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/** Chip select line will be asserted */
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#define SELECT_SLAVE 0
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/** Chip select line will be deasserted */
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#define DESELECT_SLAVE SPI_MODE_SSPOL
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2006-06-14 00:22:50 +00:00
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/**
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* Select/deselect slave
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*
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2006-12-04 15:36:51 +00:00
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* @v spibit SPI bit-bashing interface
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2006-06-14 00:22:50 +00:00
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* @v slave Slave number
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* @v state Slave select state
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*
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2006-12-04 15:36:51 +00:00
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* @c state must be @c SELECT_SLAVE or @c DESELECT_SLAVE.
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2006-06-14 00:22:50 +00:00
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*/
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static void spi_bit_set_slave_select ( struct spi_bit_basher *spibit,
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unsigned int slave,
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unsigned int state ) {
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struct bit_basher *basher = &spibit->basher;
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2006-12-04 15:36:51 +00:00
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state ^= ( spibit->bus.mode & SPI_MODE_SSPOL );
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2006-06-14 00:22:50 +00:00
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DBG ( "Setting slave %d select %s\n", slave,
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( state ? "high" : "low" ) );
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2006-12-04 15:36:51 +00:00
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spi_bit_delay();
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2006-06-14 00:22:50 +00:00
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write_bit ( basher, SPI_BIT_SS ( slave ), state );
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2006-12-04 15:36:51 +00:00
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spi_bit_delay();
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2006-06-14 00:22:50 +00:00
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}
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/**
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2006-12-04 15:36:51 +00:00
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* Transfer bits over SPI bit-bashing bus
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2006-06-14 00:22:50 +00:00
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*
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2006-12-04 15:36:51 +00:00
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* @v bus SPI bus
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2006-06-14 00:22:50 +00:00
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* @v data_out TX data buffer (or NULL)
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* @v data_in RX data buffer (or NULL)
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* @v len Length of transfer (in @b bits)
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*
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* This issues @c len clock cycles on the SPI bus, shifting out data
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* from the @c data_out buffer to the MOSI line and shifting in data
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* from the MISO line to the @c data_in buffer. If @c data_out is
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* NULL, then the data sent will be all zeroes. If @c data_in is
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* NULL, then the incoming data will be discarded.
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*/
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static void spi_bit_transfer ( struct spi_bit_basher *spibit,
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const void *data_out, void *data_in,
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unsigned int len ) {
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struct spi_bus *bus = &spibit->bus;
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struct bit_basher *basher = &spibit->basher;
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2006-12-04 15:36:51 +00:00
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unsigned int sclk = ( ( bus->mode & SPI_MODE_CPOL ) ? 1 : 0 );
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unsigned int cpha = ( ( bus->mode & SPI_MODE_CPHA ) ? 1 : 0 );
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unsigned int offset;
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unsigned int mask;
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unsigned int bit;
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int step;
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2006-12-04 15:36:51 +00:00
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DBG ( "Transferring %d bits in mode %x\n", len, bus->mode );
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2006-06-14 00:22:50 +00:00
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for ( step = ( ( len * 2 ) - 1 ) ; step >= 0 ; step-- ) {
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/* Calculate byte offset within data and bit mask */
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offset = ( step / 16 );
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mask = ( 1 << ( ( step % 16 ) / 2 ) );
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/* Shift data in or out */
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if ( sclk == cpha ) {
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const uint8_t *byte;
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/* Shift data out */
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if ( data_out ) {
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byte = ( data_out + offset );
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bit = ( *byte & mask );
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} else {
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bit = 0;
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}
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write_bit ( basher, SPI_BIT_MOSI, bit );
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} else {
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uint8_t *byte;
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/* Shift data in */
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bit = read_bit ( basher, SPI_BIT_MISO );
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if ( data_in ) {
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byte = ( data_in + offset );
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*byte &= ~mask;
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*byte |= ( bit & mask );
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}
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}
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/* Toggle clock line */
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spi_bit_delay();
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sclk = ~sclk;
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write_bit ( basher, SPI_BIT_SCLK, sclk );
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}
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}
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2006-12-04 15:36:51 +00:00
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/**
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* Read/write data via SPI bit-bashing bus
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*
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* @v bus SPI bus
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* @v device SPI device
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* @v command Command
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* @v address Address to read/write (<0 for no address)
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* @v data_out TX data buffer (or NULL)
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* @v data_in RX data buffer (or NULL)
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* @v len Length of transfer (in @b words)
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* @ret rc Return status code
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*/
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static int spi_bit_rw ( struct spi_bus *bus, struct spi_device *device,
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unsigned int command, int address,
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const void *data_out, void *data_in,
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unsigned int len ) {
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struct spi_bit_basher *spibit
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= container_of ( bus, struct spi_bit_basher, bus );
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struct spi_device_type *devtype = device->type;
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uint32_t tmp;
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/* Assert chip select on specified slave */
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spi_bit_set_slave_select ( spibit, device->slave, SELECT_SLAVE );
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/* Transmit command */
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assert ( devtype->command_len <= ( 8 * sizeof ( tmp ) ) );
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tmp = cpu_to_le32 ( command );
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spi_bit_transfer ( spibit, &tmp, NULL, devtype->command_len );
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/* Transmit address, if present */
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if ( address >= 0 ) {
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assert ( devtype->address_len <= ( 8 * sizeof ( tmp ) ) );
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tmp = cpu_to_le32 ( address );
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spi_bit_transfer ( spibit, &tmp, NULL, devtype->address_len );
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}
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/* Transmit/receive data */
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spi_bit_transfer ( spibit, data_out, data_in,
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( len * devtype->word_len ) );
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/* Deassert chip select on specified slave */
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spi_bit_set_slave_select ( spibit, device->slave, DESELECT_SLAVE );
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return 0;
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}
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2006-06-14 00:22:50 +00:00
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/**
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* Initialise SPI bit-bashing interface
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*
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* @v spibit SPI bit-bashing interface
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*/
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void init_spi_bit_basher ( struct spi_bit_basher *spibit ) {
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assert ( &spibit->basher.op->read != NULL );
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assert ( &spibit->basher.op->write != NULL );
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spibit->bus.rw = spi_bit_rw;
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2006-06-14 00:22:50 +00:00
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}
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