I'l looking at defining about a dozen ioctl calls for a local device driver.
When looking at the _IO, _IO, _IOW, _IOR, and _IOWR macros, I'm interested if
there are any "reserved" or "local" values for the first parameter?
In short, I'd hate to use a seemly unused value, just to suddenly be in
conflict with a major set of ioctls (particularly terminal, as this is the
type of driver it will be). Also, would it be wise to reuse an existing value?
For instance, 'C' is used apparently by the SCSI system in
/usr/include/cam/scsi/scsi_targetio.h, ISDN in
/usr/include/machine/i4b_debug.h, and sound in
/usr/include/machine/soundcard.h.
In short, I want a value thats 'safe', in so far as I probably won't have to
go back and redefine it later. I've been burned on thsi before (see majors.i386
in /usr/src/sys/i386/conf where 200-255 are now reserved... They weren't until
post 2.2.6-ish when I spent 3 weeks doing tech support because one of the new
device drivers in 2.2.8 conflicted with locally released code).
Anyhow, good thoughts?
-Brian
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