Ing. Daniel Rozsnyó wrote:
Oh James, these answers are much out of concept.
I'm not sure that you have understood me.
James Richard Tyrer wrote:
Ing. Daniel Rozsnyó wrote: <SNIP>
You can obtain a unique IP for the PC side using DHCP.
DHCP wouldn't be started till after the OS was booted, so that
isn't going to work.
Why run it on PC? The usual network setup for DHPC (one segment):
PC - dhcp client for EV interface
EV - dhcp client
ROUTER - dhcp server for LAN - wan to the Internet
Here the question is how to detect which IP is of the EV. It can be
by scanning the network, magic packets, uPNP...
If you have 2 network cards in the PC, then the link to EV is
dedicated:
EV - static ip
PC - static ip for EV interface - dhcp client internet interface
ROUTER - dhcp server for LAN - wan to the Internet
Well, I guess that you could have a DHCP client in firmware that could
run without an OS, but I'm not convinced that that is a good idea.
You set the IP for EV in the firmware build (default) and later you
can change it over network / serial / usb / IR remote.
Also if you have two routers, the second one can provide a dynamic IP
for the second segment (the PC-EV link). When you merge the DHCP
server to the EV box, you can run the display on dedicated link
without configuration.
NOTE: If you have more NIC's in the PC, the "BIOS extension ROM for
VGA emulation for EV" has to know some way which NIC to use. Probably
the supported one, or in case of multiple supported NIC's it will
have to try all the interfaces and look for an alive EV box.
I think that you may have answered your own question. But, if using the
box as the PC's video card, you could require that it be plugged into eth0.
You can discover the display devices IP either by scanning the
network, or sending a broadcast "magic" packet (our own discovery
protocol, or maybe a standard way - uPnP protocol should be for
this kind of stuff).
As I think I said, you could have the card that was emulating VGA
respond to 127.0.0.x.
VGA does not go thru IP :)
VGA is a set of BIOS calls (+ memory area + io registers).
The VGA BIOS calls are calls -- we are hoping that we don't need to
emulate actual hardware access which DOS programs do.
Anyway, you can't take IP addresses of 127.0.0.x out of your computer
as 127.0.0.0/8 is handled by 'lo' driver. At least here on my Windows
laptop, I assume Linux do the same. This is basic networking setup.
Doesn't that leave 127.0.0.9/F available? Actually, if the EV box is
functioning as the video card, it isn't really outside of the computer.
But, you are correct that you can't interfere with drivers that would
start up during boot. Perhaps there is a better choice of a fixed IP
address.
The PC side emulates a video card.
Actually not. The BIOS provides the standard VGA interrupt
routines. How the hardware handles this isn't really relevant.
Isn't relevant to the booting PC since it only uses the interrupts.
Actually yes. The PC side is by minimalistic view only a BIOS
extension code ROM, with not that minimal look, you count in a
supported NIC:
You need to make 2 devices for the above:
First is sitting as an independent node on the Ethernet, and can
do X and video decoding [the original goal of this list].
The second thing is a NIC+BIOS add-on card for PCI/PCIE, which
emulates a VGA card/keyboard/mouse. Who wants to boot or install
his PC over ethernet buys this card, otherwise it will be not
required, as the kernel loads and networking is up, you can
access the other box the same way.
You could make such a card. However, as I said, there are VGA BIOS
routines which are in the BIOS on the video card for booting.
After you boot an OS, you are going to be using a driver for that
OS. The only problem is that running DOS would be limited to using
the BIOS routines -- probably not a great concern anymore.
So you agree now with the above.
To the extent that it is one possible solution. However, since most
current motherboards have built in NICs and expansion cards are
supposedly going to become obsolete (I doubt this Intel hype), it
doesn't seem like the best solution
BTW: The support to transfer the BOOT image to the EV box is only
needed if you can provide also back-channel communication for HID (at
least keyboard), which can be used to configure the BIOS, editing via
GRUB loader, resolving root mount point issues with certain initrd..
Wouldn't the keyboard and mouse be on the PC. If using X, you would be
connecting to a remote X server. There is no need for a hardware
connection to the X server for the keyboard and mouse.
Otherwise nobody needs to know about the PC's boot, if he/she can do
nothing about it and has to go to the console.
It is necessary to configure the PC motherboard although this is
becoming less and less necessary.
BTW: is it possible for the X box to open a new window when some
PC boots up and display its console?
Basically, no. It would have to start X for this to happen. Since
the boot mode uses only the VGA BIOS routines to directly access
the hardware this wouldn't work.
Hey, that is bad concept! Why you want to run a video-transfer driver
and on top of that the X, if you can run the X directly on the
target?
I presume that you didn't mean running both of them at the same time.
Well, that is the common way of doing it:
1. The BIOS communicates with the console using the VGA BIOS calls
2. After the OS boots, it communicates with the console using the
console driver.
3. After the OS startup is complete, X is started.
So if the box runs the X server, the BIOS extension will contain a X
client (assuming underlying networking is up and running) and then
you can pop up a boot image on the target device. Using X protocol.
I hadn't thought of that, but yes that might work. You would also need
a console driver for step #2. Actually, if this would work, it sounds
like a good idea. There are issues:
What would you do to run OSes other than *NIX variants?
Can you pack this primitive X client into 64 KiB of memory?
This way you could make a setup which does not use our special hw
X box, but a normal PC with X
After you boot and are running X, that is possible.
What is running on the EV box is not the concern of what is installed
on the PC. It is a separate, stand-alone node on ethernet.
You misunderstood what I meant by 'running'. Perhaps I should have said
'using'. Yes, the X server could be running on the EV box, but you have
to have an X client running on the PC for the two to communicate using
X. So, yes, it matters what is installed on the PC.
and when you equip your servers with the NIC/BIOS add-on, you get
a KVM like thing.
What do you say?
You can't run X (communicate with an X terminal) until after you
boot the OS and start X or an X compatible thin client system.
The EV will implement an X server if it has a processor. It is an old
technology, so today you should be able to implement it using a 8
bit microcontroller :)
But, you need to have a client running on the PC.
--
James Tyrer
Linux (mostly) From Scratch
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