sio0: port may not be enabled

Jeremy Chadwick koitsu at
Fri Apr 20 18:08:07 UTC 2007

On Fri, Apr 20, 2007 at 09:45:43AM -0700, Marcel Moolenaar wrote:
> On Apr 20, 2007, at 8:23 AM, Jeremy Chadwick wrote:
> >Look closely at the dmesg line, note what device sio0 is claiming  
> >to be
> >associated with (acpi0, not isa0):
> >
> >>sio0: <16550A-compatible COM port> port 0x3f8-0x3ff irq 4 flags  
> >>0x10 on acpi0
> >
> >This is one of the drawbacks to using ACPI.
> This is not a drawback. It's partly why ACPI was designed and  
> implemented:
> to describe legacy hardware.

It's a drawback in the sense that if the technology is newer than what
FreeBSD can handle/is made for, then administrators are forced to look
at alternatives (other hardware or operating systems).

> >Some systems apparently tie the serial port to ACPI functionality in a
> >different way.  For example, I have a couple boxes which have sio0
> >attached to acpi0 that work fine.  In some other cases, I have ones
> >which result in a non-working serial port unless I disable ACPI (thus
> >sio0 shows up as being attached to isa0).
> Could you try uart(4) instead. It seems quite excessive to have to
> disable ACPI just to get a serial port working. I'd like to know
> if this is related to the sio(4) driver or something else.

Can you provide some directions explaining how to configure the
kernel (other than "device uart") and loader.conf or device.hints
for appropriate variables?  I'll be more than happy to try this out.

| Jeremy Chadwick                                    jdc at |
| Parodius Networking                  |
| UNIX Systems Administrator                      Mountain View, CA, USA |
| Making life hard for others since 1977.                  PGP: 4BD6C0CB |

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