device hints for isa modules

[M. Warner Losh]

In message: <46CB625D.7040505 at FreeBSD.org>
            "Constantine A. Murenin" <cnst at freebsd.org> writes:
: Dear freebsd-hackers@,
: 
: Is there a way to statically compile device hints into an isa(4) module?
: 
:  From what it looks, there is no place in the source tree to put the 
: hints for isa(4) modules -- you either have to place default hints into 
: GENERIC.hints, implying that the driver will be compiled into a GENERIC 
: kernel, or place it into NOTES.  In the former case, having a module is 
: then useless; in the latter, the module simply ain't going to work.

No.  It isn't useless.  If you have a driver listed in GENERIC.hints,
but not GENERIC, then there's no driver that will be attached and the
hint will effectively be ignored.  If you later load a driver of the
proper name, it will use the hints.  We do this all the time at work
so that we can load our drivers and have them probe/attach for the
custom ISA hardware we produce (it doesn't do ISA PNP).

You actually need to place them in both places.

: This is complicated further by the fact that changing isa hints after 
: the boot has no effect on isa driver modules that use standard methods 
: of resource acquisition. (Specifically, notice that kenv(1) won't give 
: you an error message when you try to create a new hint or update an 
: existing one, and the new or updated hint will in fact be visible back 
: from kenv(1), but it won't have any effect on bus_alloc_resource(9) 
: calls, thus modules depending on isa hints will fail to find their 
: hardware.)

This is actually a bug.  It would be desirable to place hints into the
hint space after boot.

: I'm specifically looking for a solution to a usable module for my lm(4) 
: driver in soc2007/cnst-sensors perforce branch...

Just add them to GENERIC.hints.  Then if/when your driver is loaded,
it will properly probe/attach.  If it is never loaded, then there's no
real harm.

I have a kernel without sio.  Yet I have the following hints:

hint.sio.0.at="isa"
hint.sio.0.flags="0x10"
hint.sio.0.irq="4"
hint.sio.0.port="0x3F8"
hint.sio.1.at="isa"
hint.sio.1.irq="3"
hint.sio.1.port="0x2F8"
hint.sio.2.at="isa"
hint.sio.2.disabled="1"
hint.sio.2.irq="5"
hint.sio.2.port="0x3E8"
hint.sio.3.at="isa"
hint.sio.3.disabled="1"
hint.sio.3.irq="9"
hint.sio.3.port="0x2E8"

The only side effect you'll see is with devinfo -v:

nexus0
  acpi0
    pcib0 pnpinfo _HID=PNP0A03 _UID=1 at handle=\_SB_.PCI0
      pci0
        isab0 pnpinfo vendor=0x1002 device=0x4377 subvendor=0x0000 subdevice=0x0000 class=0x060100 at slot=20 function=3 handle=\_SB_.PCI0.LPC0
          isa0
            sio0
            sio1
            sio2
            sio3

devinfo doesn't show it.  kldstat on my box doesn't list any sio
devices.  When I load sio.ko, sio0-sio3 do not attach because I don't
have any real COMx devices.

This is a little confusing, but has proven to be fairly useful in
practice.  It would be a little nicer if devinfo -v reported if the
device was attached or not...

Warner