Date: Sat, 11 Mar 2000 11:42:55 +0100 From: Jeroen Ruigrok/Asmodai <asmodai@wxs.nl> To: new-bus@freebsd.org Subject: Abstraction API for drivers Message-ID: <20000311114255.T68308@daemon.ninth-circle.org>
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[Matthew, please feel free to correct me]
Hi guys,
after Matthew Dodd and me discussed some abstracting the access to the
newbus functionality with Poul-Henning Kamp.
Basically what phk said was that we were repeating lots of code in our
PCI drivers. Matthew and me agreed on that aspect, but were concerned
about making the abstraction PCI only. If such an API would be created,
it should be a complete solution.
Basically one of the things that will repeat itself a lot in PCI drivers
is:
static int xl_probe(dev)
device_t dev;
{
struct xl_type *t;
t = xl_devs;
while(t->xl_name != NULL) {
if ((pci_get_vendor(dev) == t->xl_vid) &&
(pci_get_device(dev) == t->xl_did)) {
device_set_desc(dev, t->xl_name);
return(0);
}
t++;
}
return(ENXIO);
}
In the probe case of a driver we will always have some sort of if
statement like the above excellent xl driver example.
We will always pci_get_[vendor|device](dev) and comparing it to the
vendor/device id of the struct array of devices.
After we find matches, we will always want to set the name with
device_set_desc(dev, name).
In the case for PCI devices this will create a very repeatable piece of
code all along the drivers.
Of course, given the total different way how, for example, ISA, EISA,
S-BUS, and such work this might provide some difficulty creating a
sufficient general API to allow for bus-independant abstraction. And
creating functionwrappers just for bus specific cases might be the only
solution, but if we can avoid it, it would be cool. =)
Ideas, comments, suggestions?
Also, Matthew explained he had some issues with rman (resource manager),
but I'll let him explain that...
--
Jeroen Ruigrok vd Werven/Asmodai asmodai@[wxs.nl|bart.nl|freebsd.org]
Documentation nutter/C-rated Coder BSD: Technical excellence at its best
The BSD Programmer's Documentation Project <http://home.wxs.nl/~asmodai>;
There is no greater sorrow than to recall, in misery, the time when we
were happy...
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