src/drivers/bus/pci.c - ipxe - Git at Google

 /*
  * Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
  *
  * Based in part on pci.c from Etherboot 5.4, by Ken Yap and David
  * Munro, in turn based on the Linux kernel's PCI implementation.
  *
  * 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., 51 Franklin Street, Fifth Floor, Boston, MA
  * 02110-1301, USA.
  *
  * You can also choose to distribute this program under the terms of
  * the Unmodified Binary Distribution Licence (as given in the file
  * COPYING.UBDL), provided that you have satisfied its requirements.
  */

 FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

 #include <stdint.h>
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
 #include <ipxe/tables.h>
 #include <ipxe/device.h>
 #include <ipxe/pci.h>

 /** @file
  *
  * PCI bus
  *
  */

 static void pcibus_remove ( struct root_device *rootdev );

 /**
  * Read PCI BAR
  *
  * @v pci		PCI device
  * @v reg		PCI register number
  * @ret bar		Base address register
  *
  * Reads the specified PCI base address register, including the flags
  * portion.  64-bit BARs will be handled automatically.  If the value
  * of the 64-bit BAR exceeds the size of an unsigned long (i.e. if the
  * high dword is non-zero on a 32-bit platform), then the value
  * returned will be zero plus the flags for a 64-bit BAR.  Unreachable
  * 64-bit BARs are therefore returned as uninitialised 64-bit BARs.
  */
 static unsigned long pci_bar ( struct pci_device *pci, unsigned int reg ) {
 	uint32_t low;
 	uint32_t high;

 	pci_read_config_dword ( pci, reg, &low );
 	if ( ( low & (PCI_BASE_ADDRESS_SPACE_IO|PCI_BASE_ADDRESS_MEM_TYPE_MASK))
 	     == PCI_BASE_ADDRESS_MEM_TYPE_64 ) {
 		pci_read_config_dword ( pci, reg + 4, &high );
 		if ( high ) {
 			if ( sizeof ( unsigned long ) > sizeof ( uint32_t ) ) {
 				return ( ( ( uint64_t ) high << 32 ) | low );
 			} else {
 				DBGC ( pci, PCI_FMT " unhandled 64-bit BAR "
 				       "%08x%08x\n",
 				       PCI_ARGS ( pci ), high, low );
 				return PCI_BASE_ADDRESS_MEM_TYPE_64;
 			}
 		}
 	}
 	return low;
 }

 /**
  * Find the start of a PCI BAR
  *
  * @v pci		PCI device
  * @v reg		PCI register number
  * @ret start		BAR start address
  *
  * Reads the specified PCI base address register, and returns the
  * address portion of the BAR (i.e. without the flags).
  *
  * If the address exceeds the size of an unsigned long (i.e. if a
  * 64-bit BAR has a non-zero high dword on a 32-bit machine), the
  * return value will be zero.
  */
 unsigned long pci_bar_start ( struct pci_device *pci, unsigned int reg ) {
 	unsigned long bar;

 	bar = pci_bar ( pci, reg );
 	if ( bar & PCI_BASE_ADDRESS_SPACE_IO ) {
 		return ( bar & ~PCI_BASE_ADDRESS_IO_MASK );
 	} else {
 		return ( bar & ~PCI_BASE_ADDRESS_MEM_MASK );
 	}
 }

 /**
  * Read membase and ioaddr for a PCI device
  *
  * @v pci		PCI device
  *
  * This scans through all PCI BARs on the specified device.  The first
  * valid memory BAR is recorded as pci_device::membase, and the first
  * valid IO BAR is recorded as pci_device::ioaddr.
  *
  * 64-bit BARs are handled automatically.  On a 32-bit platform, if a
  * 64-bit BAR has a non-zero high dword, it will be regarded as
  * invalid.
  */
 static void pci_read_bases ( struct pci_device *pci ) {
 	unsigned long bar;
 	int reg;

 	/* Clear any existing base addresses */
 	pci->ioaddr = 0;
 	pci->membase = 0;

 	/* Get first memory and I/O BAR addresses */
 	for ( reg = PCI_BASE_ADDRESS_0; reg <= PCI_BASE_ADDRESS_5; reg += 4 ) {
 		bar = pci_bar ( pci, reg );
 		if ( bar & PCI_BASE_ADDRESS_SPACE_IO ) {
 			if ( ! pci->ioaddr )
 				pci->ioaddr =
 					( bar & ~PCI_BASE_ADDRESS_IO_MASK );
 		} else {
 			if ( ! pci->membase )
 				pci->membase =
 					( bar & ~PCI_BASE_ADDRESS_MEM_MASK );
 			/* Skip next BAR if 64-bit */
 			if ( bar & PCI_BASE_ADDRESS_MEM_TYPE_64 )
 				reg += 4;
 		}
 	}
 }

 /**
  * Enable PCI device
  *
  * @v pci		PCI device
  *
  * Set device to be a busmaster in case BIOS neglected to do so.  Also
  * adjust PCI latency timer to a reasonable value, 32.
  */
 void adjust_pci_device ( struct pci_device *pci ) {
 	unsigned short new_command, pci_command;
 	unsigned char pci_latency;

 	pci_read_config_word ( pci, PCI_COMMAND, &pci_command );
 	new_command = ( pci_command | PCI_COMMAND_MASTER |
 			PCI_COMMAND_MEM | PCI_COMMAND_IO );
 	if ( pci_command != new_command ) {
 		DBGC ( pci, PCI_FMT " device not enabled by BIOS! Updating "
 		       "PCI command %04x->%04x\n",
 		       PCI_ARGS ( pci ), pci_command, new_command );
 		pci_write_config_word ( pci, PCI_COMMAND, new_command );
 	}

 	pci_read_config_byte ( pci, PCI_LATENCY_TIMER, &pci_latency);
 	if ( pci_latency < 32 ) {
 		DBGC ( pci, PCI_FMT " latency timer is unreasonably low at "
 		       "%d. Setting to 32.\n", PCI_ARGS ( pci ), pci_latency );
 		pci_write_config_byte ( pci, PCI_LATENCY_TIMER, 32);
 	}
 }

 /**
  * Read PCI device configuration
  *
  * @v pci		PCI device
  * @ret rc		Return status code
  */
 int pci_read_config ( struct pci_device *pci ) {
 	uint32_t busdevfn;
 	uint8_t hdrtype;
 	uint32_t tmp;

 	/* Ignore all but the first function on non-multifunction devices */
 	if ( PCI_FUNC ( pci->busdevfn ) != 0 ) {
 		busdevfn = pci->busdevfn;
 		pci->busdevfn = PCI_FIRST_FUNC ( pci->busdevfn );
 		pci_read_config_byte ( pci, PCI_HEADER_TYPE, &hdrtype );
 		pci->busdevfn = busdevfn;
 		if ( ! ( hdrtype & PCI_HEADER_TYPE_MULTI ) )
 			return -ENODEV;
 	}

 	/* Check for physical device presence */
 	pci_read_config_dword ( pci, PCI_VENDOR_ID, &tmp );
 	if ( ( tmp == 0xffffffff ) || ( tmp == 0 ) )
 		return -ENODEV;

 	/* Populate struct pci_device */
 	pci->vendor = ( tmp & 0xffff );
 	pci->device = ( tmp >> 16 );
 	pci_read_config_dword ( pci, PCI_REVISION, &tmp );
 	pci->class = ( tmp >> 8 );
 	pci_read_config_byte ( pci, PCI_INTERRUPT_LINE, &pci->irq );
 	pci_read_config_byte ( pci, PCI_HEADER_TYPE, &pci->hdrtype );
 	pci_read_bases ( pci );

 	/* Initialise generic device component */
 	snprintf ( pci->dev.name, sizeof ( pci->dev.name ), "%04x:%02x:%02x.%x",
 		   PCI_SEG ( pci->busdevfn ), PCI_BUS ( pci->busdevfn ),
 		   PCI_SLOT ( pci->busdevfn ), PCI_FUNC ( pci->busdevfn ) );
 	pci->dev.desc.bus_type = BUS_TYPE_PCI;
 	pci->dev.desc.location = pci->busdevfn;
 	pci->dev.desc.vendor = pci->vendor;
 	pci->dev.desc.device = pci->device;
 	pci->dev.desc.class = pci->class;
 	pci->dev.desc.ioaddr = pci->ioaddr;
 	pci->dev.desc.irq = pci->irq;
 	INIT_LIST_HEAD ( &pci->dev.siblings );
 	INIT_LIST_HEAD ( &pci->dev.children );

 	return 0;
 }

 /**
  * Find next device on PCI bus
  *
  * @v pci		PCI device to fill in
  * @v busdevfn		Starting bus:dev.fn address
  * @ret busdevfn	Bus:dev.fn address of next PCI device
  * @ret rc		Return status code
  */
 int pci_find_next ( struct pci_device *pci, uint32_t *busdevfn ) {
 	static struct pci_range range;
 	uint8_t hdrtype;
 	uint8_t sub;
 	uint32_t end;
 	unsigned int count;
 	int rc;

 	/* Find next PCI device, if any */
 	do {
 		/* Find next PCI bus:dev.fn address range, if necessary */
 		if ( ( *busdevfn - range.start ) >= range.count ) {
 			pci_discover ( *busdevfn, &range );
 			if ( *busdevfn < range.start )
 				*busdevfn = range.start;
 			if ( ( *busdevfn - range.start ) >= range.count )
 				break;
 		}

 		/* Check for PCI device existence */
 		memset ( pci, 0, sizeof ( *pci ) );
 		pci_init ( pci, *busdevfn );
 		if ( ( rc = pci_read_config ( pci ) ) != 0 )
 			continue;

 		/* If device is a bridge, expand the PCI bus:dev.fn
 		 * address range as needed.
 		 */
 		pci_read_config_byte ( pci, PCI_HEADER_TYPE, &hdrtype );
 		hdrtype &= PCI_HEADER_TYPE_MASK;
 		if ( hdrtype == PCI_HEADER_TYPE_BRIDGE ) {
 			pci_read_config_byte ( pci, PCI_SUBORDINATE, &sub );
 			end = PCI_BUSDEVFN ( PCI_SEG ( *busdevfn ),
 					     ( sub + 1 ), 0, 0 );
 			count = ( end - range.start );
 			if ( count > range.count ) {
 				DBGC ( pci, PCI_FMT " found subordinate bus "
 				       "%#02x\n", PCI_ARGS ( pci ), sub );
 				range.count = count;
 			}
 		}

 		/* Return this device */
 		return 0;

 	} while ( ++(*busdevfn) );

 	return -ENODEV;
 }

 /**
  * Find driver for PCI device
  *
  * @v pci		PCI device
  * @ret rc		Return status code
  */
 int pci_find_driver ( struct pci_device *pci ) {
 	struct pci_driver *driver;
 	struct pci_device_id *id;
 	unsigned int i;

 	for_each_table_entry ( driver, PCI_DRIVERS ) {
 		if ( ( driver->class.class ^ pci->class ) & driver->class.mask )
 			continue;
 		for ( i = 0 ; i < driver->id_count ; i++ ) {
 			id = &driver->ids[i];
 			if ( ( id->vendor != PCI_ANY_ID ) &&
 			     ( id->vendor != pci->vendor ) )
 				continue;
 			if ( ( id->device != PCI_ANY_ID ) &&
 			     ( id->device != pci->device ) )
 				continue;
 			pci_set_driver ( pci, driver, id );
 			return 0;
 		}
 	}
 	return -ENOENT;
 }

 /**
  * Probe a PCI device
  *
  * @v pci		PCI device
  * @ret rc		Return status code
  *
  * Searches for a driver for the PCI device.  If a driver is found,
  * its probe() routine is called.
  */
 int pci_probe ( struct pci_device *pci ) {
 	int rc;

 	DBGC ( pci, PCI_FMT " (%04x:%04x) has driver \"%s\"\n",
 	       PCI_ARGS ( pci ), pci->vendor, pci->device, pci->id->name );
 	DBGC ( pci, PCI_FMT " has mem %lx io %lx irq %d\n",
 	       PCI_ARGS ( pci ), pci->membase, pci->ioaddr, pci->irq );

 	if ( ( rc = pci->driver->probe ( pci ) ) != 0 ) {
 		DBGC ( pci, PCI_FMT " probe failed: %s\n",
 		       PCI_ARGS ( pci ), strerror ( rc ) );
 		return rc;
 	}

 	return 0;
 }

 /**
  * Remove a PCI device
  *
  * @v pci		PCI device
  */
 void pci_remove ( struct pci_device *pci ) {
 	pci->driver->remove ( pci );
 	DBGC ( pci, PCI_FMT " removed\n", PCI_ARGS ( pci ) );
 }

 /**
  * Probe PCI root bus
  *
  * @v rootdev		PCI bus root device
  *
  * Scans the PCI bus for devices and registers all devices it can
  * find.
  */
 static int pcibus_probe ( struct root_device *rootdev ) {
 	struct pci_device *pci = NULL;
 	uint32_t busdevfn = 0;
 	int rc;

 	/* Skip automatic probing if prohibited */
 	if ( ! pci_can_probe() )
 		return 0;

 	do {
 		/* Allocate struct pci_device */
 		if ( ! pci )
 			pci = malloc ( sizeof ( *pci ) );
 		if ( ! pci ) {
 			rc = -ENOMEM;
 			goto err;
 		}

 		/* Find next PCI device, if any */
 		if ( ( rc = pci_find_next ( pci, &busdevfn ) ) != 0 )
 			break;

 		/* Look for a driver */
 		if ( ( rc = pci_find_driver ( pci ) ) != 0 ) {
 			DBGC ( pci, PCI_FMT " (%04x:%04x class %06x) has no "
 			       "driver\n", PCI_ARGS ( pci ), pci->vendor,
 			       pci->device, pci->class );
 			continue;
 		}

 		/* Add to device hierarchy */
 		pci->dev.parent = &rootdev->dev;
 		list_add ( &pci->dev.siblings, &rootdev->dev.children );

 		/* Look for a driver */
 		if ( ( rc = pci_probe ( pci ) ) == 0 ) {
 			/* pcidev registered, we can drop our ref */
 			pci = NULL;
 		} else {
 			/* Not registered; re-use struct pci_device */
 			list_del ( &pci->dev.siblings );
 		}

 	} while ( ++busdevfn );

 	free ( pci );
 	return 0;

  err:
 	free ( pci );
 	pcibus_remove ( rootdev );
 	return rc;
 }

 /**
  * Remove PCI root bus
  *
  * @v rootdev		PCI bus root device
  */
 static void pcibus_remove ( struct root_device *rootdev ) {
 	struct pci_device *pci;
 	struct pci_device *tmp;

 	list_for_each_entry_safe ( pci, tmp, &rootdev->dev.children,
 				   dev.siblings ) {
 		pci_remove ( pci );
 		list_del ( &pci->dev.siblings );
 		free ( pci );
 	}
 }

 /** PCI bus root device driver */
 static struct root_driver pci_root_driver = {
 	.probe = pcibus_probe,
 	.remove = pcibus_remove,
 };

 /** PCI bus root device */
 struct root_device pci_root_device __root_device = {
 	.dev = { .name = "PCI" },
 	.driver = &pci_root_driver,
 };
	/*
	* Copyright (C) 2006 Michael Brown <mbrown@fensystems.co.uk>.
	*
	* Based in part on pci.c from Etherboot 5.4, by Ken Yap and David
	* Munro, in turn based on the Linux kernel's PCI implementation.
	*
	* 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., 51 Franklin Street, Fifth Floor, Boston, MA
	* 02110-1301, USA.
	*
	* You can also choose to distribute this program under the terms of
	* the Unmodified Binary Distribution Licence (as given in the file
	* COPYING.UBDL), provided that you have satisfied its requirements.
	*/

	FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );

	#include <stdint.h>
	#include <stdlib.h>
	#include <stdio.h>
	#include <string.h>
	#include <errno.h>
	#include <ipxe/tables.h>
	#include <ipxe/device.h>
	#include <ipxe/pci.h>

	/** @file
	*
	* PCI bus
	*
	*/

	static void pcibus_remove ( struct root_device *rootdev );

	/**
	* Read PCI BAR
	*
	* @v pci PCI device
	* @v reg PCI register number
	* @ret bar Base address register
	*
	* Reads the specified PCI base address register, including the flags
	* portion. 64-bit BARs will be handled automatically. If the value
	* of the 64-bit BAR exceeds the size of an unsigned long (i.e. if the
	* high dword is non-zero on a 32-bit platform), then the value
	* returned will be zero plus the flags for a 64-bit BAR. Unreachable
	* 64-bit BARs are therefore returned as uninitialised 64-bit BARs.
	*/
	static unsigned long pci_bar ( struct pci_device *pci, unsigned int reg ) {
	uint32_t low;
	uint32_t high;

	pci_read_config_dword ( pci, reg, &low );
	if ( ( low & (PCI_BASE_ADDRESS_SPACE_IO\|PCI_BASE_ADDRESS_MEM_TYPE_MASK))
	== PCI_BASE_ADDRESS_MEM_TYPE_64 ) {
	pci_read_config_dword ( pci, reg + 4, &high );
	if ( high ) {
	if ( sizeof ( unsigned long ) > sizeof ( uint32_t ) ) {
	return ( ( ( uint64_t ) high << 32 ) \| low );
	} else {
	DBGC ( pci, PCI_FMT " unhandled 64-bit BAR "
	"%08x%08x\n",
	PCI_ARGS ( pci ), high, low );
	return PCI_BASE_ADDRESS_MEM_TYPE_64;
	}
	}
	}
	return low;
	}

	/**
	* Find the start of a PCI BAR
	*
	* @v pci PCI device
	* @v reg PCI register number
	* @ret start BAR start address
	*
	* Reads the specified PCI base address register, and returns the
	* address portion of the BAR (i.e. without the flags).
	*
	* If the address exceeds the size of an unsigned long (i.e. if a
	* 64-bit BAR has a non-zero high dword on a 32-bit machine), the
	* return value will be zero.
	*/
	unsigned long pci_bar_start ( struct pci_device *pci, unsigned int reg ) {
	unsigned long bar;

	bar = pci_bar ( pci, reg );
	if ( bar & PCI_BASE_ADDRESS_SPACE_IO ) {
	return ( bar & ~PCI_BASE_ADDRESS_IO_MASK );
	} else {
	return ( bar & ~PCI_BASE_ADDRESS_MEM_MASK );
	}
	}

	/**
	* Read membase and ioaddr for a PCI device
	*
	* @v pci PCI device
	*
	* This scans through all PCI BARs on the specified device. The first
	* valid memory BAR is recorded as pci_device::membase, and the first
	* valid IO BAR is recorded as pci_device::ioaddr.
	*
	* 64-bit BARs are handled automatically. On a 32-bit platform, if a
	* 64-bit BAR has a non-zero high dword, it will be regarded as
	* invalid.
	*/
	static void pci_read_bases ( struct pci_device *pci ) {
	unsigned long bar;
	int reg;

	/* Clear any existing base addresses */
	pci->ioaddr = 0;
	pci->membase = 0;

	/* Get first memory and I/O BAR addresses */
	for ( reg = PCI_BASE_ADDRESS_0; reg <= PCI_BASE_ADDRESS_5; reg += 4 ) {
	bar = pci_bar ( pci, reg );
	if ( bar & PCI_BASE_ADDRESS_SPACE_IO ) {
	if ( ! pci->ioaddr )
	pci->ioaddr =
	( bar & ~PCI_BASE_ADDRESS_IO_MASK );
	} else {
	if ( ! pci->membase )
	pci->membase =
	( bar & ~PCI_BASE_ADDRESS_MEM_MASK );
	/* Skip next BAR if 64-bit */
	if ( bar & PCI_BASE_ADDRESS_MEM_TYPE_64 )
	reg += 4;
	}
	}
	}

	/**
	* Enable PCI device
	*
	* @v pci PCI device
	*
	* Set device to be a busmaster in case BIOS neglected to do so. Also
	* adjust PCI latency timer to a reasonable value, 32.
	*/
	void adjust_pci_device ( struct pci_device *pci ) {
	unsigned short new_command, pci_command;
	unsigned char pci_latency;

	pci_read_config_word ( pci, PCI_COMMAND, &pci_command );
	new_command = ( pci_command \| PCI_COMMAND_MASTER \|
	PCI_COMMAND_MEM \| PCI_COMMAND_IO );
	if ( pci_command != new_command ) {
	DBGC ( pci, PCI_FMT " device not enabled by BIOS! Updating "
	"PCI command %04x->%04x\n",
	PCI_ARGS ( pci ), pci_command, new_command );
	pci_write_config_word ( pci, PCI_COMMAND, new_command );
	}

	pci_read_config_byte ( pci, PCI_LATENCY_TIMER, &pci_latency);
	if ( pci_latency < 32 ) {
	DBGC ( pci, PCI_FMT " latency timer is unreasonably low at "
	"%d. Setting to 32.\n", PCI_ARGS ( pci ), pci_latency );
	pci_write_config_byte ( pci, PCI_LATENCY_TIMER, 32);
	}
	}

	/**
	* Read PCI device configuration
	*
	* @v pci PCI device
	* @ret rc Return status code
	*/
	int pci_read_config ( struct pci_device *pci ) {
	uint32_t busdevfn;
	uint8_t hdrtype;
	uint32_t tmp;

	/* Ignore all but the first function on non-multifunction devices */
	if ( PCI_FUNC ( pci->busdevfn ) != 0 ) {
	busdevfn = pci->busdevfn;
	pci->busdevfn = PCI_FIRST_FUNC ( pci->busdevfn );
	pci_read_config_byte ( pci, PCI_HEADER_TYPE, &hdrtype );
	pci->busdevfn = busdevfn;
	if ( ! ( hdrtype & PCI_HEADER_TYPE_MULTI ) )
	return -ENODEV;
	}

	/* Check for physical device presence */
	pci_read_config_dword ( pci, PCI_VENDOR_ID, &tmp );
	if ( ( tmp == 0xffffffff ) \|\| ( tmp == 0 ) )
	return -ENODEV;

	/* Populate struct pci_device */
	pci->vendor = ( tmp & 0xffff );
	pci->device = ( tmp >> 16 );
	pci_read_config_dword ( pci, PCI_REVISION, &tmp );
	pci->class = ( tmp >> 8 );
	pci_read_config_byte ( pci, PCI_INTERRUPT_LINE, &pci->irq );
	pci_read_config_byte ( pci, PCI_HEADER_TYPE, &pci->hdrtype );
	pci_read_bases ( pci );

	/* Initialise generic device component */
	snprintf ( pci->dev.name, sizeof ( pci->dev.name ), "%04x:%02x:%02x.%x",
	PCI_SEG ( pci->busdevfn ), PCI_BUS ( pci->busdevfn ),
	PCI_SLOT ( pci->busdevfn ), PCI_FUNC ( pci->busdevfn ) );
	pci->dev.desc.bus_type = BUS_TYPE_PCI;
	pci->dev.desc.location = pci->busdevfn;
	pci->dev.desc.vendor = pci->vendor;
	pci->dev.desc.device = pci->device;
	pci->dev.desc.class = pci->class;
	pci->dev.desc.ioaddr = pci->ioaddr;
	pci->dev.desc.irq = pci->irq;
	INIT_LIST_HEAD ( &pci->dev.siblings );
	INIT_LIST_HEAD ( &pci->dev.children );

	return 0;
	}

	/**
	* Find next device on PCI bus
	*
	* @v pci PCI device to fill in
	* @v busdevfn Starting bus:dev.fn address
	* @ret busdevfn Bus:dev.fn address of next PCI device
	* @ret rc Return status code
	*/
	int pci_find_next ( struct pci_device pci, uint32_t busdevfn ) {
	static struct pci_range range;
	uint8_t hdrtype;
	uint8_t sub;
	uint32_t end;
	unsigned int count;
	int rc;

	/* Find next PCI device, if any */
	do {
	/* Find next PCI bus:dev.fn address range, if necessary */
	if ( ( *busdevfn - range.start ) >= range.count ) {
	pci_discover ( *busdevfn, &range );
	if ( *busdevfn < range.start )
	*busdevfn = range.start;
	if ( ( *busdevfn - range.start ) >= range.count )
	break;
	}

	/* Check for PCI device existence */
	memset ( pci, 0, sizeof ( *pci ) );
	pci_init ( pci, *busdevfn );
	if ( ( rc = pci_read_config ( pci ) ) != 0 )
	continue;

	/* If device is a bridge, expand the PCI bus:dev.fn
	* address range as needed.
	*/
	pci_read_config_byte ( pci, PCI_HEADER_TYPE, &hdrtype );
	hdrtype &= PCI_HEADER_TYPE_MASK;
	if ( hdrtype == PCI_HEADER_TYPE_BRIDGE ) {
	pci_read_config_byte ( pci, PCI_SUBORDINATE, &sub );
	end = PCI_BUSDEVFN ( PCI_SEG ( *busdevfn ),
	( sub + 1 ), 0, 0 );
	count = ( end - range.start );
	if ( count > range.count ) {
	DBGC ( pci, PCI_FMT " found subordinate bus "
	"%#02x\n", PCI_ARGS ( pci ), sub );
	range.count = count;
	}
	}

	/* Return this device */
	return 0;

	} while ( ++(*busdevfn) );

	return -ENODEV;
	}

	/**
	* Find driver for PCI device
	*
	* @v pci PCI device
	* @ret rc Return status code
	*/
	int pci_find_driver ( struct pci_device *pci ) {
	struct pci_driver *driver;
	struct pci_device_id *id;
	unsigned int i;

	for_each_table_entry ( driver, PCI_DRIVERS ) {
	if ( ( driver->class.class ^ pci->class ) & driver->class.mask )
	continue;
	for ( i = 0 ; i < driver->id_count ; i++ ) {
	id = &driver->ids[i];
	if ( ( id->vendor != PCI_ANY_ID ) &&
	( id->vendor != pci->vendor ) )
	continue;
	if ( ( id->device != PCI_ANY_ID ) &&
	( id->device != pci->device ) )
	continue;
	pci_set_driver ( pci, driver, id );
	return 0;
	}
	}
	return -ENOENT;
	}

	/**
	* Probe a PCI device
	*
	* @v pci PCI device
	* @ret rc Return status code
	*
	* Searches for a driver for the PCI device. If a driver is found,
	* its probe() routine is called.
	*/
	int pci_probe ( struct pci_device *pci ) {
	int rc;

	DBGC ( pci, PCI_FMT " (%04x:%04x) has driver \"%s\"\n",
	PCI_ARGS ( pci ), pci->vendor, pci->device, pci->id->name );
	DBGC ( pci, PCI_FMT " has mem %lx io %lx irq %d\n",
	PCI_ARGS ( pci ), pci->membase, pci->ioaddr, pci->irq );

	if ( ( rc = pci->driver->probe ( pci ) ) != 0 ) {
	DBGC ( pci, PCI_FMT " probe failed: %s\n",
	PCI_ARGS ( pci ), strerror ( rc ) );
	return rc;
	}

	return 0;
	}

	/**
	* Remove a PCI device
	*
	* @v pci PCI device
	*/
	void pci_remove ( struct pci_device *pci ) {
	pci->driver->remove ( pci );
	DBGC ( pci, PCI_FMT " removed\n", PCI_ARGS ( pci ) );
	}

	/**
	* Probe PCI root bus
	*
	* @v rootdev PCI bus root device
	*
	* Scans the PCI bus for devices and registers all devices it can
	* find.
	*/
	static int pcibus_probe ( struct root_device *rootdev ) {
	struct pci_device *pci = NULL;
	uint32_t busdevfn = 0;
	int rc;

	/* Skip automatic probing if prohibited */
	if ( ! pci_can_probe() )
	return 0;

	do {
	/* Allocate struct pci_device */
	if ( ! pci )
	pci = malloc ( sizeof ( *pci ) );
	if ( ! pci ) {
	rc = -ENOMEM;
	goto err;
	}

	/* Find next PCI device, if any */
	if ( ( rc = pci_find_next ( pci, &busdevfn ) ) != 0 )
	break;

	/* Look for a driver */
	if ( ( rc = pci_find_driver ( pci ) ) != 0 ) {
	DBGC ( pci, PCI_FMT " (%04x:%04x class %06x) has no "
	"driver\n", PCI_ARGS ( pci ), pci->vendor,
	pci->device, pci->class );
	continue;
	}

	/* Add to device hierarchy */
	pci->dev.parent = &rootdev->dev;
	list_add ( &pci->dev.siblings, &rootdev->dev.children );

	/* Look for a driver */
	if ( ( rc = pci_probe ( pci ) ) == 0 ) {
	/* pcidev registered, we can drop our ref */
	pci = NULL;
	} else {
	/* Not registered; re-use struct pci_device */
	list_del ( &pci->dev.siblings );
	}

	} while ( ++busdevfn );

	free ( pci );
	return 0;

	err:
	free ( pci );
	pcibus_remove ( rootdev );
	return rc;
	}

	/**
	* Remove PCI root bus
	*
	* @v rootdev PCI bus root device
	*/
	static void pcibus_remove ( struct root_device *rootdev ) {
	struct pci_device *pci;
	struct pci_device *tmp;

	list_for_each_entry_safe ( pci, tmp, &rootdev->dev.children,
	dev.siblings ) {
	pci_remove ( pci );
	list_del ( &pci->dev.siblings );
	free ( pci );
	}
	}

	/** PCI bus root device driver */
	static struct root_driver pci_root_driver = {
	.probe = pcibus_probe,
	.remove = pcibus_remove,
	};

	/** PCI bus root device */
	struct root_device pci_root_device __root_device = {
	.dev = { .name = "PCI" },
	.driver = &pci_root_driver,
	};