Sorry for the late reply. My weekend was a little more chaotic than
I'd planned. Please accept my appologies.
I'd like to point you to the handbook information first:
Which has some background on the whole process, and walks you through
it. I just read it again, and here are my -stable relative comments.
Section 14.8 talks about the probe routine. Here are my comments on
You don't need to worry about PNP, per se, but you do need to filter
out the pnp devices from patching your device in your probe routine.
This is typically done like so:
sn_isa_probe (device_t dev)
if (isa_get_logicalid(dev)) /* skip PnP probes */
if (sn_probe(dev, 0) != 0)
the above code is from the sn driver, which has a fairly generic
probe routine that's used for both ISA and PCMCIA cards.
You should ignore the section that talks about looking at all the
possible device locations. This is no longer done in the probe
routine, but in the related identify routine. But only for self
identifying devices (which are fairly rare if they aren't PNP
enumerated). Typically, the simple, non-pnp devices are statically
linked into the kernel and you get the resources from the kernel
All resources that you allocate in the probe routine must be released
before you exit the probe routine. I tend to use the methods
described near the end of section 14.8 to have one routine that
allocates resources and one that frees all resources.
Section 14.9 is also fair description of how the attach routine should
be written. Again, a generic resource allocation and freeing routine
will save time here. Avoid use of rman_get_virtual since it makes it
harder to user your device in a PAE kernel (use busdma instead if your
ISA device supports DMA).
As for the glue for the driver, you can pretty much take most of it
from section 14.2 which gives the lowdown on the boilerplate stuff
that's required. Chances are excellent that you won't have to worry
about shutdown, suspend or resume. If you don't want to make your
driver loadable, there's little to no harm in 4.x to not having a
All in all, the chapter has all the information you need. I'd have
organized it a little differently than it is, but a careful reading
should help get you going.
The sn driver, all things considered, isn't a horrible driver to look
at for these things. It isn't perfect, and there are people that can
find faults with it, but it would serve as a good guide to writing isa
drivers. ed and ep are well maintained, but suffer too much from
being really popular hardware and have a lot of distracting warts, as
well as vestiges of past APIs here and there that will be confusing.