Initial revision

include/spi.h

+/*
+ * (C) Copyright 2001
+ * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#ifndef _SPI_H_
+#define _SPI_H_
+
+/*
+ * The function call pointer type used to drive the chip select.
+ */
+typedef void (*spi_chipsel_type)(int cs);
+
+
+/*-----------------------------------------------------------------------
+ * Initialization, must be called once on start up.
+ */
+void spi_init(void);
+
+
+/*-----------------------------------------------------------------------
+ * SPI transfer
+ *
+ * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
+ * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
+ *
+ * The source of the outgoing bits is the "dout" parameter and the
+ * destination of the input bits is the "din" parameter.  Note that "dout"
+ * and "din" can point to the same memory location, in which case the
+ * input data overwrites the output data (since both are buffered by
+ * temporary variables, this is OK).
+ *
+ * If the chipsel() function is not NULL, it is called with a parameter
+ * of '1' (chip select active) at the start of the transfer and again with
+ * a parameter of '0' at the end of the transfer.
+ *
+ * If the chipsel() function _is_ NULL, it the responsibility of the
+ * caller to make the appropriate chip select active before calling
+ * spi_xfer() and making it inactive after spi_xfer() returns.
+ *
+ * spi_xfer() interface:
+ *   chipsel: Routine to call to set/clear the chip select:
+ *              if chipsel is NULL, it is not used.
+ *              if(cs),  make the chip select active (typically '0').
+ *              if(!cs), make the chip select inactive (typically '1').
+ *   dout:    Pointer to a string of bits to send out.  The bits are
+ *              held in a byte array and are sent MSB first.
+ *   din:     Pointer to a string of bits that will be filled in.
+ *   bitlen:  How many bits to write and read.
+ *
+ *   Returns: 0 on success, not 0 on failure
+ */
+int  spi_xfer(spi_chipsel_type chipsel, int bitlen, uchar *dout, uchar *din);
+
+#endif	/* _SPI_H_ */