Date: Wed, 23 May 2001 10:38:00 -0700 (PDT) From: SJ <sandejain@rocketmail.com> To: Alexander Langer <alex@big.endian.de> Cc: freebsd-questions@FreeBSD.ORG, freebsd-hackers@FreeBSD.ORG Subject: Re: Device driver questions Message-ID: <20010523173800.84311.qmail@web13404.mail.yahoo.com> In-Reply-To: <20010523085857.B1103@zerogravity.kawo2.rwth-aachen.d>
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--- Alexander Langer <alex@big.endian.de> wrote:
> Thus spake SJ (sandejain@rocketmail.com):
>
> Hi!
>
> > 1. "ioconf.c" contains struct config_resource and
> > config_device definitions for declarations in
> > "config" file. But I noticed that for some
> devices
> > e.g. device atadisk
> > device atapicd
> > ...
> > the corresponding lines in ioconf.c are
> missing??
>
> I think it's because ata is a self-identifying bus.
> Not sure, though. Are any PCI-only devices listed?
The configuration contains the following two lines:
device pci0
device pci1
for which the corresponding ioconf.c output is:
struct config_resource pci0_resources[] = {
};
#define pci0_count 0
struct config_resource pci1_resources[] = {
};
#define pci1_count 0
>
> > 3. File naming question:
> > whats the reasoning behind having "bus.h" and
> > "bus_private.h"....whats the significance of
> > "private" here.
>
> drivers include bus.h, kernel does also include
> bus_private.h
But still the name "private" confuses me...according
to
me it should have been "bus_public.c". Any comments?
thanks for your help
sandeep
>
> > 4. concept behind having devclasses...I know that
>
> > devclasses for a particular bus holds devices
> and
> > device drivers for that bus. But then whats the
>
> > need for defining a devclass for each driver we
>
> > write ?
>
> Because you can hold multpiple devices that are
> enumerated, e.g. xl0,
> xl1, ...
> The devclass is unique for each driver, but not for
> different busses.
> You can have ed0 on ISA and ed1 on PCI for example,
> using the same
> devclass.
> If ISA and PCI subdrivers are using a different
> devclass, the
> enumeration breaks.
>
> > 5. Any poniters to literature which explains the
> > design philosophy and code specific help for
> device
> > drivers in freebsd - I am referring to files
> > kern/subr_bus.c, bus.h, bus_private.h, isa/*
> etc.
>
> Use the source, luke :-)
> Seriously, subr_bus.c is quite nice to read if you
> read it togethers
> with, say, sys/pci/pci.c.
> That makes the concept quite clear.
>
> The developer's handbook might be worth reading for
> you, also there
> are some tutorials on the website which explain a
> little.
>
> Alex
>
> --
> cat: /home/alex/.sig: No such file or directory
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