Added sketch of bit-bashing interface common code

src/Makefile

@@ -140,6 +140,7 @@ SRCDIRS		+= drivers/block
 SRCDIRS		+= drivers/scsi
 SRCDIRS		+= drivers/ata
 SRCDIRS		+= drivers/nvs
+SRCDIRS		+= drivers/bitbash
 SRCDIRS		+= interface/pxe
 SRCDIRS		+= tests
 

src/drivers/bitbash/bitbash.c

@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * 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 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., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include <timer.h>
+#include <gpxe/bitbash.h>
+
+/** @file
+ *
+ * Bit-bashing interfaces
+ *
+ */
+
+/**
+ * Set/clear output bit
+ *
+ * @v basher		Bit-bashing interface
+ * @v bit_id		Bit number
+ * @v data		Value to write
+ * 
+ * If @c data is 0, a logic 0 will be written.  If @c data is
+ * non-zero, a logic 1 will be written.
+ */
+void write_bit ( struct bit_basher *basher, unsigned int bit_id,
+		 unsigned long data ) {
+	basher->write ( basher, bit_id, ( data ? -1UL : 0 ) );
+	udelay ( basher->udelay );
+}
+
+/**
+ * Read input bit
+ *
+ * @v basher		Bit-bashing interface
+ * @v bit_id		Bit number
+ * @ret data		Value read
+ *
+ * @c data will always be either 0 or 1.
+ */
+int read_bit ( struct bit_basher *basher, unsigned int bit_id ) {
+	return ( basher->read ( basher, bit_id ) ? 1 : 0 );
+}

src/include/gpxe/bitbash.h

@@ -0,0 +1,44 @@
+#ifndef _GPXE_BITBASH_H
+#define _GPXE_BITBASH_H
+
+/** @file
+ *
+ * Bit-bashing interfaces
+ *
+ */
+
+/** A bit-bashing interface */
+struct bit_basher {
+	/**
+	 * Set/clear output bit
+	 *
+	 * @v basher		Bit-bashing interface
+	 * @v bit_id		Bit number
+	 * @v data		Value to write
+	 * 
+	 * @c data will be 0 if a logic 0 should be written (i.e. the
+	 * bit should be cleared), or -1UL if a logic 1 should be
+	 * written (i.e. the bit should be set).  This is done so that
+	 * the method may simply binary-AND @c data with the
+	 * appropriate bit mask.
+	 */
+	void ( * write ) ( struct bit_basher *basher, unsigned int bit_id,
+			   unsigned long data );
+	/**
+	 * Read input bit
+	 *
+	 * @v basher		Bit-bashing interface
+	 * @v bit_id		Bit number
+	 * @ret zero		Input is a logic 0
+	 * @ret non-zero	Input is a logic 1
+	 */
+	int ( * read ) ( struct bit_basher *basher, unsigned int bit_id );
+	/** Delay between subsequent calls to write(), in microseconds */
+	unsigned int udelay;
+};
+
+extern void write_bit ( struct bit_basher *basher, unsigned int bit_id,
+			unsigned long data );
+extern int read_bit ( struct bit_basher *basher, unsigned int bit_id );
+
+#endif /* _GPXE_BITBASH_H */