22 Dec
2005
22 Dec
'05
12:36 p.m.
On Thu, 22 Dec 2005 00:26:44 +0000 (GMT)
ard at p850ug1.demon.co.uk (Tony Duell) wrote:
You are, IMHO, missing the point. Under linux, you have an ioctl() call
that lets you send any ocmmand bytes you like to the FDC. You can
therefore get that chip to do anything that it's capable of. And that
call takes care of setting up the DMA controller if you need it, making
sure the DMA buffer doesn't cross a page boundary, and all the other
nasty little details.
Actually sending a ReadID command is not a problem.
The problem is that the ReadID command reads the next sector ID to come
round to the head. The only way (that I can see) to make sure you've not
missed any is to keep on sending ReadID commands (and getting the
results) until you get the same ID again that you got from the first one
-- i.e. the disk has gone round once.
The problem on a multi-tasking OS is that your task might be switched out
half-way though this. You might therefore miss a sector ID entirely. And
how ever many times you repeat it, you can never be sure you've not been
unlucky and missed the same one each time.
-tony
To get back to disk imaging, I may be stupid, but
I do wonder if
it's actually possible to write such a program to run under
linux or any other multi-tasking system.
Since it's possible under Linux or one of the BSD Unixes to
completely compile out support for the floppy controller, it
should also be possible to pull said kernel code out, and create a
(super)user-mode module application out of it to do whatever you
want with the disk controller. More of this sort of thing should
be done, in my estimation. (my two cent opinion, I know, since I
should do-it-myself).