Trimming the default /boot/device.hints

[John Baldwin]

On Wednesday 28 January 2009 1:39:03 am M. Warner Losh wrote:
> In message: <200901260947.32870.jhb at freebsd.org>
>             John Baldwin <jhb at freebsd.org> writes:
> : After the changes to make hints always reserve device names, soem folks ran 
> : into issues with devices changing names due to previously unused hints now 
> : always being honored (e.g. hints for non-existent ISA le(4) cards always 
> : reserving le0).  What I would like to do to help minimize this further is to 
> : trim the default set of hints.  The number of machines that will run 8.0 that 
> : have ISA slots is incredibly small, probably zero.  To that end, I would like 
> : to remove all hints for ISA adapters from i386 and amd64 (amd64 already has 
> : most of them removed).  Also, the hint for vga0 is not needed as the vga_isa 
> : driver uses an identify routine to always add itself.  Note that end-users 
> : can always add hints back later if desired/needed.  However, changing the 
> : defaults means that some hardware may no longer work out of the box.  My 
> : guess though is that the set of such hardware is the empty set.
> 
> Your guess likely would be incorrect.  There's still a number of
> embedded machines that have pc-104 busses attached to them.  However,
> the set is getting much smaller...

Yes, but do any of those devices have 'adv0', 'bt0', 'aha0', 'aic0', 'ed0',
'cs0', 'sn0', 'ie0', 'fe0', or 'le0' on the PC-104 bus?  If not, then the
set remains empty.  I'm not removing support for ISA devices.  I'm removing
hints for a specific set of ISA add-on cards.
 
> : If we wanted, we could go further and assume that all machines have either 
> : PnPBIOS or ACPI and remove most of the other hints as well.  We already sort 
> : of assume that on amd64 (which has no atrtc0 hints, but still has hints for 
> : fdc0, ppc0, and some other devices).
> 
> A pure PNPBIOS enumerated system is almost working today.  It works on
> x86 most of the time.  I've run systems that had only minimal hints
> for sio2 and sio3 and a couple of other minor variants.

Yes, many of my machines also work fine with only a syscons hint.  The issue
is if we still want to support machines that have neither ACPI nor PnPBIOS
(or where someone has to disable both) out of the box.

> : Here is the proposed diff:
> 
> I don't like this change.  However, you've hit on part of the reason I
> don't like the change.  I don't think it goes far enough, and at the
> same time loses valuable history.
> 
> To address the latter, I'd do a cp GENERIC.hints LEGACY.hints and add
> comments to the top that this is for systems that don't have PNPBIOS
> or ACPI or that there's problems with those.

These are already present in /sys/<arch>/conf/NOTES.  We already have all
the various historical hints already documented there.  The real issue is
what set of hints we will include in the default set to support hardware
out of the box.  The reason I have not gone further and assumed PnPBIOS
or ACPI is that it is a separate question, and I'd rather do this in stages.

> To address the former, I'd propose something more like:
> 
> hint.fd.0.at="fdc0"
> hint.fd.0.drive="0"
> hint.fd.1.at="fdc0"
> hint.fd.1.drive="1"
> hint.atkbd.0.at="atkbdc"
> hint.psm.0.at="atkbdc"
> hint.sc.0.at="isa"
> hint.sc.0.flags="0x100"
> hint.uart.0.port="0x3F8"
> hint.uart.0.flags="0x10"
> hint.uart.1.port="0x2F8"
> 
> Not sure that the 'sc' lines are needed, but I was too chicken to try
> without them.  They used to be needed...  The above wires up
> everything that isn't on the ISA bus, and gives hints that uart0
> should be the one at 0x3f8, etc.

I think the fd lines are very much not needed since fdc can enumerate floppy
drives on its own.  The rest of the hints don't actually work aside from
sc0 as hints require an 'at' hint before they wire anything.  The sc0 hints
are still required, though it would be nice to fix syscons to not need a hint
and just always add a device in an identify routine instead.

-- 
John Baldwin