Henrik W Lund wrote:
Well, I was *hoping* to be able to display my own messages to the display. I suppose I should have explained a little better - the display is a 2 line x 16 character display, so the output from the kernel startup would probably just be a blur ;-) It may even be difficult to determine where it is hanging if it were to hang (due to the small size and information capacity).
I am planning on purchasing a crystalfontz LCD panel to be able to have a rudimentary interface with the system without having a keyboard/monitor/shell.
I'm not sure whether to go the serial or USB route. What I want to do is to be able to display status as the system is coming up, then have a user level application accept input from the panel and display various statistics, then when the system is brought down, for the panel to notify the user that it is safe to turn off the machine.
For the startup and shutdown I would need to hack stuff into the kernel. I have done a fair bit of C programming over the years, but never worked in the kernel. So I have 2 real questions:
Would it be easier to control the USB or Serial panel from the Kernel?
And - does anyone have any recommendations as to where I could even start looking in the kernel to do what I want?
Thanks, Tim
(Please CC: me as I am not subscribed to this list - Thanks!)
Greetings!
I'd guess that the serial version would be the way to go, since FreeBSD has builtin support for displaying to serial console (typically used for headless systems, allowing admins to use a serial communications program like HyperTerminal under Windows for out- and input). This is, of course, assuming that the LCD panel interfaces like a serial terminal. If it does, you've got about half the job done, as FreeBSD will happily print bootup and shutdown information out-of-the-box.
Further, if it announces touches to the screen as regular keypresses, you're even luckier. All that really would remain for you to do was to write the UI (as I don't think a ready-made solution exists for what you want. I may be wrong, though). If this is to be a GUI (on top of X, that is), you'd have to find out if X will display to serial terminal. If it doesn't, I'm sure any idea you can come up with is just as good/better than mine. ;-)The display actually fits iniside a 5 1/4" drive bay, and the pushbuttons do not emulate a keyboard. I am not to worried about it, however, as I don't really need to be able to read the keypad during the startup and shutdown process.
Worst case scenario; the LCD screen interfaces like a toaster. My best bet would be to do a kernel module. More info on how to do those can be found here:Thanks for the link - I will be sure to go through everything there. I *have* written device drivers for other operating systems and done a fair bit of interface code in C in the past.
http://www.freebsd.org/doc/en_US.ISO8859-1/books/arch-handbook/index.html
If it is possible, I would prefer to use the USB model, but that would require me homehow figuring out how to use the device drivers from my kernel module. A cursory look through the Architecture Handbook doesn't cover that (the USB device driver for the lcd panel in question already does exist in FreeBSD).
I would also have to make sure that the USB subsystem (and probably the serial devices as AFAICT the USB driver for the lcd looks like a serial port to applications) was loaded as early on as I could so I could use it for most of the FreeBSD startup - and what about the shutdown? Will the device exist and work when the kernel is in the 'halted' state?
I have thought about the possibility of talking directly to the serial port (I have done 16*50 interface code before) during my serial module, but that may open another can of worms.
I encourage others to elaborate (and correct me, of course) as they see fit. Not having done much actual work on FreeBSD myself, what I propose here is what my programmer's mind sees as probable based on what documentation and experimenting I have seen and done.
Thanks Henrik, I apprecate the response ;-)
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