Added PnP BIOS scanning code, separated out from the UNDI driver

src/arch/i386/firmware/pcbios/pnpbios.c

@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2007 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 <stdint.h>
+#include <string.h>
+#include <errno.h>
+#include <realmode.h>
+#include <pnpbios.h>
+
+/** @file
+ *
+ * PnP BIOS
+ *
+ */
+
+/** PnP BIOS structure */
+struct pnp_bios {
+	/** Signature
+	 *
+	 * Must be equal to @c PNP_BIOS_SIGNATURE
+	 */
+	uint32_t signature;
+	/** Version as BCD (e.g. 1.0 is 0x10) */
+	uint8_t version;
+	/** Length of this structure */
+	uint8_t length;
+	/** System capabilities */
+	uint16_t control;
+	/** Checksum */
+	uint8_t checksum;
+} __attribute__ (( packed ));
+
+/** Signature for a PnP BIOS structure */
+#define PNP_BIOS_SIGNATURE \
+	( ( '$' << 0 ) + ( 'P' << 8 ) + ( 'n' << 16 ) + ( 'P' << 24 ) )
+
+/**
+ * Test address for PnP BIOS structure
+ *
+ * @v offset		Offset within BIOS segment to test
+ * @ret rc		Return status code
+ */
+static int is_pnp_bios ( unsigned int offset ) {
+	union {
+		struct pnp_bios pnp_bios;
+		uint8_t bytes[256]; /* 256 is maximum length possible */
+	} u;
+	size_t len;
+	unsigned int i;
+	uint8_t sum = 0;
+
+	/* Read start of header and verify signature */
+	copy_from_real ( &u.pnp_bios, BIOS_SEG, offset, sizeof ( u.pnp_bios ));
+	if ( u.pnp_bios.signature != PNP_BIOS_SIGNATURE )
+		return -EINVAL;
+
+	/* Read whole header and verify checksum */
+	len = u.pnp_bios.length;
+	copy_from_real ( &u.bytes, BIOS_SEG, offset, len );
+	for ( i = 0 ; i < len ; i++ ) {
+		sum += u.bytes[i];
+	}
+	if ( sum != 0 )
+		return -EINVAL;
+
+	DBG ( "Found PnP BIOS at %04x:%04x\n", BIOS_SEG, offset );
+
+	return 0;
+}
+
+/**
+ * Locate Plug-and-Play BIOS
+ *
+ * @ret pnp_offset	Offset of PnP BIOS structure within BIOS segment
+ *
+ * The PnP BIOS structure will be at BIOS_SEG:pnp_offset.  If no PnP
+ * BIOS is found, -1 is returned.
+ */
+int find_pnp_bios ( void ) {
+	static int pnp_offset = 0;
+
+	if ( pnp_offset )
+		return pnp_offset;
+
+	for ( pnp_offset = 0 ; pnp_offset < 0x10000 ; pnp_offset += 0x10 ) {
+		if ( is_pnp_bios ( pnp_offset ) == 0 )
+			return pnp_offset;
+	}
+
+	pnp_offset = -1;
+	return pnp_offset;
+}

src/arch/i386/include/pnpbios.h

@@ -0,0 +1,15 @@
+#ifndef _PNPBIOS_H
+#define _PNPBIOS_H
+
+/** @file
+ *
+ * PnP BIOS
+ *
+ */
+
+/* BIOS segment address */
+#define BIOS_SEG 0xf000
+
+extern int find_pnp_bios ( void );
+
+#endif /* _PNPBIOS_H */