Re: [PATCH] earlyprintk: Clean up pciserial

From: Bjorn Helgaas
Date: Thu Aug 25 2022 - 15:51:53 EST


On Thu, Aug 25, 2022 at 09:36:35PM +0200, Peter Zijlstra wrote:
> On Thu, Aug 25, 2022 at 12:39:59PM -0500, Bjorn Helgaas wrote:
>
> > > - (((classcode >> 8) & 0xff) != 0x02)) /* 16550 I/F at BAR0 */ {
>
> > > diff --git a/include/linux/pci_ids.h b/include/linux/pci_ids.h
> > > index 6feade66efdb..1d2c7df8cd41 100644
> > > --- a/include/linux/pci_ids.h
> > > +++ b/include/linux/pci_ids.h
> > > @@ -75,6 +75,9 @@
> > > #define PCI_CLASS_COMMUNICATION_MODEM 0x0703
> > > #define PCI_CLASS_COMMUNICATION_OTHER 0x0780
> > >
> > > +/* I/F for SERIAL/MODEM */
> >
> > I/F? Grep says it's fairly common, but doesn't seem completely
> > obvious. I guess it means "interface"?
>
> It does, I carried the nomenclature from the above line; happy to change
> it if you want.
>
> https://wiki.osdev.org/PCI#Class_Codes
>
> Calls it 'Prog IF'.

Personally, I would spell it out just to make it less arcane. I
wouldn't know where to find the definition, and the PCI specs don't
seem to use the abbreviation. But no big deal either way.

Bjorn