OSDev.org

Hey.


So I started tinkering around, following the different articles here. Something however came to my mind: the technical limitations of the basic VGA framebuffer. The 80x25 character limit being the most annoying drawback. I could of course implement video drivers, but I think we can all agree on the fact it isn't the easiest thing to do.

I started looking at a more... standard way to make a good looking UI: using a terminal over RS-232. The wiki article on serial ports and how to interact with them was really complete. Plus, they can become really useful when it comes to debugging. However, connecting two computers over RS-232 may not seem like the easiest way to interact with one for some people.

What do you think, from a technical point of view and not a user one, would be the best way to have a quick and easy user interface? Is a serial terminal the best way to do it?

Marginally better than a teleprinter I suppose.

[I think that constitutes a vote against. I suspect it might be unacceptably slow]

Serial ports used to be really easy to interface. The speed was low, but it was easy. Today, the typical computer doesn't have a real serial port, and you need to add it by using an USB-to-serial converter. To widely support that, you need drivers for 4 different USB standards (OHCI, UHCI, EHCI and XHCI) and for hubs (because a lot of computers have internal hubs instead of real ports). Then you need to support various manufacturers of USB to serial converters (although most are FTDI-compatible).

VGA used to be really nasty with palettes and bit-planes, but nowadays you can get an LFB buffer directly from EFI (or via VBE, which is slightly more complicated). That means most computers today has an video-card that is easy to use. You will not get the best performance without custom video accelerators, but you can always make it work with an LFB buffer.

Another good way to interface is with networks. I'd say it's easier to support networks (selecting a few major manufacturers like RealTek and Intel), and writing a generic driver for their cards, than to support all kinds of strange USB standards.

For what it is worth, rack mounted servers sometimes have physical serial ports. Tunneling over ethernet (Serail-over-LAN) is also possible. It is indistinguishable to physical port on the server and can be useful for automating testing, debugging of system code using kernel debugger, etc. Not everyone needs or uses this.

I am confused as to what you actually mean here. Are you saying you want to use a simulated RS-232 as the hardware abstraction layer for the console? That isn't what RS-232 (or rather, TIA-232, which is the current version of the standard) is for.

I suspect what you actually mean is something like VT-100 or ANSI Graphics, rather than RS-232. RS-232 has nothing at all to do with display, any more than a telephone has anything to do with what you say into it - it is a data carrier (and an asymmetrical one at that - DCE and DTE are not the equal partners), nothing more.

What are you actually trying to achieve here?

I think that you're right. This would be fast and it'll remove VGA restriction, it can be used over LAN as simeonz said, so I agree with you: serial port will be the best variant here for me.