utils/devbios/README.bios - openbios - Git at Google

 NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE!

 /dev/bios is obsolete and no longer under development.
 Please use the flashrom utility instead: https://www.flashrom.org/

 NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE!


 /dev/bios documentation						  2002/02/19

 Table of contents
 ------------------

   1. What is /dev/bios?
   2. What hardware/software do I need to run /dev/bios?
   3. Where to get the latest release of /dev/bios
   4. How to get /dev/bios work
   5. Writing to the devices
   6. About PCI chipsets (ix86 only)
   7. About APM Powermanagement (ix86 only)
   8. About different flashchips.
   9. Hints for BIOS flashing

 If you want better information on this driver, read the ChangeLog,
 mail me or read the source, Luke :-)

 1. What is /dev/bios?
 ----------------------

 This is a kernel driver for different kinds of (Flash)BIOSs that are
 available in today's hardware.

 There are well known BIOSs for
  - System BIOS (resides at 0xe0000 on Intel PCs)
  - graphics hardware
  - SCSI host adapters
  - networking interfaces with 'BOOT ROM'
  - ...

 While in former times these BIOSs were implemented by using ROM or
 EPROM (both can't be updated without opening your computer) today's
 PC hardware is often delivered with so called FLASH ROMs. These
 can simply be updated by software. This driver has the approach to
 make Linux read and write flash roms.

 One word before you read ahead: This is still alpha software and
 writing to your flash roms may destroy them. So if you notice anything
 strange, don't even think about going on, but write some mail to:

 		Stefan Reinauer <stefan.reinauer@coreboot.org>

 Please note that I am not responsible in any way for what you
 do with this code or for what this code does with your computer.

 2. What hardware/software do I need to run /dev/bios?
 ------------------------------------------------------

 Currently this driver supports ix86 (mainly Pentium,
 PPro, PII/III, Athlon, but some 486s), Itanium and Alpha
 architecture.
 It supports all flash chips from 32k to 2M (theoretically).
 Minimum kernel version is v2.2.x, but it's wise to use a
 2.4.x kernel.

 3. Where to get the latest release of /dev/bios?
 -------------------------------------------------

 /dev/bios was recently integrated into the OpenBIOS CVS
 tree for easier maintainance. General information can be
 found on the /dev/bios status page:
 http://www.freiburg.linux.de/OpenBIOS/status/devbios.html
 Latest releases of /dev/bios can be found at the download page:
 http://www.freiburg.linux.de/OpenBIOS/dev/download.html
 Latest development trees of /dev/bios can be found in the
 OpenBIOS CVS. For information how to access it, go to
 http://www.freiburg.linux.de/OpenBIOS/dev/cvs.html

 4. How do I get /dev/bios work
 -------------------------------

 Create the system bios device with

 	mknod /dev/bios c 104 0

 Now you can add devices for the other BIOSs (often known as option
 roms) in your Computer, i.e. like this:

 	mknod /dev/gfxbios c 104 1
 	mknod /dev/hddbios c 104 2
 	mknod /dev/netbios c 104 3

 The order of the devices may vary on your computer, maybe you even don't
 have a flash bios on your network card or on your scsi host adapter. You will
 have to decide this after playing  around a bit.

 Now you have to compile and insert the kernel driver module:

 	cd devbios
 	make clean && make
 	insmod bios.o

 Now you have a new device, /dev/bios and, if you have
 your kernel configured to have the /proc/ interface,
 you have a status file /proc/bios.

 Since this driver is in an early state, you should have
 a look at dmesg very often.

 5. Writing to the devices
 --------------------------

 If you insert bios.o without any options, you are not able
 to write any of the devices. To enable writing, you should
 use
 	insmod bios.o write=1

 Writing is now possible with i.e.
    dd if=yourbios.bin of=/dev/bios bs=128k count=1
 or
    dd if=yourbios.bin of=/dev/bios bs=256k count=1

 depending on the size of your flash chip.

 You can use 'cat' for flashing as well. Note: Many flashchips are
 sectored and the whole sector has to be rewritten, the 4k clusters
 of cat may be very slow (and an 112 kb sector has to be written 28
 times completely instead of 1 time with dd)

 Make sure that your file "yourbios.bin" is a valid bios image for
 your motherboard and that it is not pkzipped or exe-pkzipped.
 (Usually, a 128kb bios images consist of 112kb lha-compressed data,
 2*4kb ESCD and DMI (PnP) Data and an 8 kb emergency boot block.)

 Writing to /dev/bios does not work for many chips right now. Write
 accesses are ignored in this case. If you want an unsupported flash
 rom supported, please mail me.
 WARNING: Setting an unsupported chip to "supported" without changing
 the rest of the code will *very likely* destroy the contents of your
 chip.

 On machines with an AWARD bios you can test whether writing works
 safely by only deleting the ESCD/DMI memory on the flash chip.
 This data is rewritten by the bios when empty, corrupted or when
 you put in a new expansion device. In that case you should see a
 message stating "Updating ESCD" during the next boot.

 Please have a close look at the size of your flash chip. For 128k
 flash chips, try

 	dd if=/dev/zero of=/dev/bios bs=4096 seek=28 count=2

 For 256k flash chips, you _MUST_ use the following line instead,
 or your system bios is going byebye:

 	dd if=/dev/zero of=/dev/bios bs=4096 seek=56 count=2

 Attention: I found other machines with their ESCD memory in the
 first sectors of the flash chip. These are afaics 512k+ chips
 often connected via a firmware hub.
 Behaviour of other BIOSs may be similar, but I can't give you
 any warranty it works.

 NOTE: If you listen to music from your soundcard while flashing,
 you may get errors like this:
 	Sound: DMA (output) timed out - IRQ/DRQ config error?

 Second, sound switches off while flashing. This is because all
 IRQs are blocked while the write procedure to ensure it doesn't
 get disturbed by any other hardware.

 6. About PCI chipsets
 ----------------------

 Because this driver uses direct PCI accesses to switch shadowing
 and write protection of the bios off on PC architecture, each PCI
 chipset (or at least chipset group) has to be implemented and
 tested seperately. Successfully tested PCI chipsets are

 	* Intel 430HX/TX, 440BX/ZX, 460, 8x0
 	* UMC 486 (8881F/8886A)
 	* VIA (M)VP3
 	* AMD Irongate and others
 	* ServerWorks chipsets
 	* NSC CS5530 (geode companion)

 Any success/error reports are highly welcome. If you need a certain
 system type supported, contact me.


 7. About APM Power Management (ix86 only)
 ------------------------------------------

 This driver is known to cause kernel oopses with some of the chipset
 drivers when APM is enabled. Reason is that the flash chip is mapped
 to the low bios address space which makes the unpacked bios image vanish
 so all pointers to APM functions are invalid.
 Nowadays most of the chipset drivers only map the high bios area, so
 this problem should not occur on any but old UMC/SiS chipsets. If you
 encounter oopses while reading/probing flash devices, disable power
 management before any write attempts. To achieve so, please pass "apm=off"
 as a kernel option, if your kernel is compiled with APM support.


 8. About different flashchips
 ------------------------------

 Flash chips, /dev/bios has been successfully tested (writing) on:

 	* Winbond 29EE011
         * Intel 28F008(SA)
 	* Atmel AT29C512
 	* SST 29EE010, 39SF020

 It *should* work, if you see a "Supported: yes"  in /proc/bios, but
 I am not responsible in any way for what you do.. Please be careful.
 Please report any working flash chips so that this list can be completed.
 Currently many more flash chips than mentioned here will work.
 If you need a certain flash device supported, contact me.

 9. Hints for BIOS-Flashing
 ---------------------------

 * Always try to write to the ESCD/DMI Memory before you overwrite the rest
   of a bios (ix86) If you get ANY errors in dmesg output, DO NOT CONTINUE!
 * Always "diff" the new bios with the written image before rebooting
 * You may use comp, a little utility in the devbios source tree instead
   of diff. It has a nicer output for binary files.
 * on Intel, only write the first 120k of an image to the System ROM, this keeps
   the emergency bootblock working.

 ************** FINAL NOTE *****************************

 If you want to help this project, send me

  * /proc/bios-output
  * dmesg-output (after insmodding the driver)
  * your system-configuration
    (e.g. output of lspci or /proc/bus/pci/devices)
  * any comments
  * any ideas

 			Stefan Reinauer <stefan.reinauer@coreboot.org>
	NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE!

	/dev/bios is obsolete and no longer under development.
	Please use the flashrom utility instead: https://www.flashrom.org/

	NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE! NOTE!


	/dev/bios documentation 2002/02/19

	Table of contents
	------------------

	1. What is /dev/bios?
	2. What hardware/software do I need to run /dev/bios?
	3. Where to get the latest release of /dev/bios
	4. How to get /dev/bios work
	5. Writing to the devices
	6. About PCI chipsets (ix86 only)
	7. About APM Powermanagement (ix86 only)
	8. About different flashchips.
	9. Hints for BIOS flashing

	If you want better information on this driver, read the ChangeLog,
	mail me or read the source, Luke :-)

	1. What is /dev/bios?
	----------------------

	This is a kernel driver for different kinds of (Flash)BIOSs that are
	available in today's hardware.

	There are well known BIOSs for
	- System BIOS (resides at 0xe0000 on Intel PCs)
	- graphics hardware
	- SCSI host adapters
	- networking interfaces with 'BOOT ROM'
	- ...

	While in former times these BIOSs were implemented by using ROM or
	EPROM (both can't be updated without opening your computer) today's
	PC hardware is often delivered with so called FLASH ROMs. These
	can simply be updated by software. This driver has the approach to
	make Linux read and write flash roms.

	One word before you read ahead: This is still alpha software and
	writing to your flash roms may destroy them. So if you notice anything
	strange, don't even think about going on, but write some mail to:

	Stefan Reinauer <stefan.reinauer@coreboot.org>

	Please note that I am not responsible in any way for what you
	do with this code or for what this code does with your computer.

	2. What hardware/software do I need to run /dev/bios?
	------------------------------------------------------

	Currently this driver supports ix86 (mainly Pentium,
	PPro, PII/III, Athlon, but some 486s), Itanium and Alpha
	architecture.
	It supports all flash chips from 32k to 2M (theoretically).
	Minimum kernel version is v2.2.x, but it's wise to use a
	2.4.x kernel.

	3. Where to get the latest release of /dev/bios?
	-------------------------------------------------

	/dev/bios was recently integrated into the OpenBIOS CVS
	tree for easier maintainance. General information can be
	found on the /dev/bios status page:
	http://www.freiburg.linux.de/OpenBIOS/status/devbios.html
	Latest releases of /dev/bios can be found at the download page:
	http://www.freiburg.linux.de/OpenBIOS/dev/download.html
	Latest development trees of /dev/bios can be found in the
	OpenBIOS CVS. For information how to access it, go to
	http://www.freiburg.linux.de/OpenBIOS/dev/cvs.html

	4. How do I get /dev/bios work
	-------------------------------

	Create the system bios device with

	mknod /dev/bios c 104 0

	Now you can add devices for the other BIOSs (often known as option
	roms) in your Computer, i.e. like this:

	mknod /dev/gfxbios c 104 1
	mknod /dev/hddbios c 104 2
	mknod /dev/netbios c 104 3

	The order of the devices may vary on your computer, maybe you even don't
	have a flash bios on your network card or on your scsi host adapter. You will
	have to decide this after playing around a bit.

	Now you have to compile and insert the kernel driver module:

	cd devbios
	make clean && make
	insmod bios.o

	Now you have a new device, /dev/bios and, if you have
	your kernel configured to have the /proc/ interface,
	you have a status file /proc/bios.

	Since this driver is in an early state, you should have
	a look at dmesg very often.

	5. Writing to the devices
	--------------------------

	If you insert bios.o without any options, you are not able
	to write any of the devices. To enable writing, you should
	use
	insmod bios.o write=1

	Writing is now possible with i.e.
	dd if=yourbios.bin of=/dev/bios bs=128k count=1
	or
	dd if=yourbios.bin of=/dev/bios bs=256k count=1

	depending on the size of your flash chip.

	You can use 'cat' for flashing as well. Note: Many flashchips are
	sectored and the whole sector has to be rewritten, the 4k clusters
	of cat may be very slow (and an 112 kb sector has to be written 28
	times completely instead of 1 time with dd)

	Make sure that your file "yourbios.bin" is a valid bios image for
	your motherboard and that it is not pkzipped or exe-pkzipped.
	(Usually, a 128kb bios images consist of 112kb lha-compressed data,
	2*4kb ESCD and DMI (PnP) Data and an 8 kb emergency boot block.)

	Writing to /dev/bios does not work for many chips right now. Write
	accesses are ignored in this case. If you want an unsupported flash
	rom supported, please mail me.
	WARNING: Setting an unsupported chip to "supported" without changing
	the rest of the code will very likely destroy the contents of your
	chip.

	On machines with an AWARD bios you can test whether writing works
	safely by only deleting the ESCD/DMI memory on the flash chip.
	This data is rewritten by the bios when empty, corrupted or when
	you put in a new expansion device. In that case you should see a
	message stating "Updating ESCD" during the next boot.

	Please have a close look at the size of your flash chip. For 128k
	flash chips, try

	dd if=/dev/zero of=/dev/bios bs=4096 seek=28 count=2

	For 256k flash chips, you _MUST_ use the following line instead,
	or your system bios is going byebye:

	dd if=/dev/zero of=/dev/bios bs=4096 seek=56 count=2

	Attention: I found other machines with their ESCD memory in the
	first sectors of the flash chip. These are afaics 512k+ chips
	often connected via a firmware hub.
	Behaviour of other BIOSs may be similar, but I can't give you
	any warranty it works.

	NOTE: If you listen to music from your soundcard while flashing,
	you may get errors like this:
	Sound: DMA (output) timed out - IRQ/DRQ config error?

	Second, sound switches off while flashing. This is because all
	IRQs are blocked while the write procedure to ensure it doesn't
	get disturbed by any other hardware.

	6. About PCI chipsets
	----------------------

	Because this driver uses direct PCI accesses to switch shadowing
	and write protection of the bios off on PC architecture, each PCI
	chipset (or at least chipset group) has to be implemented and
	tested seperately. Successfully tested PCI chipsets are

	* Intel 430HX/TX, 440BX/ZX, 460, 8x0
	* UMC 486 (8881F/8886A)
	* VIA (M)VP3
	* AMD Irongate and others
	* ServerWorks chipsets
	* NSC CS5530 (geode companion)

	Any success/error reports are highly welcome. If you need a certain
	system type supported, contact me.


	7. About APM Power Management (ix86 only)
	------------------------------------------

	This driver is known to cause kernel oopses with some of the chipset
	drivers when APM is enabled. Reason is that the flash chip is mapped
	to the low bios address space which makes the unpacked bios image vanish
	so all pointers to APM functions are invalid.
	Nowadays most of the chipset drivers only map the high bios area, so
	this problem should not occur on any but old UMC/SiS chipsets. If you
	encounter oopses while reading/probing flash devices, disable power
	management before any write attempts. To achieve so, please pass "apm=off"
	as a kernel option, if your kernel is compiled with APM support.



	8. About different flashchips
	------------------------------

	Flash chips, /dev/bios has been successfully tested (writing) on:

	* Winbond 29EE011
	* Intel 28F008(SA)
	* Atmel AT29C512
	* SST 29EE010, 39SF020

	It should work, if you see a "Supported: yes" in /proc/bios, but
	I am not responsible in any way for what you do.. Please be careful.
	Please report any working flash chips so that this list can be completed.
	Currently many more flash chips than mentioned here will work.
	If you need a certain flash device supported, contact me.

	9. Hints for BIOS-Flashing
	---------------------------

	* Always try to write to the ESCD/DMI Memory before you overwrite the rest
	of a bios (ix86) If you get ANY errors in dmesg output, DO NOT CONTINUE!
	* Always "diff" the new bios with the written image before rebooting
	* You may use comp, a little utility in the devbios source tree instead
	of diff. It has a nicer output for binary files.
	* on Intel, only write the first 120k of an image to the System ROM, this keeps
	the emergency bootblock working.

	************ FINAL NOTE ***************************

	If you want to help this project, send me

	* /proc/bios-output
	* dmesg-output (after insmodding the driver)
	* your system-configuration
	(e.g. output of lspci or /proc/bus/pci/devices)
	* any comments
	* any ideas

	Stefan Reinauer <stefan.reinauer@coreboot.org>