Date: Tue, 14 Jul 2009 08:49:51 -0400 From: John Baldwin <jhb@freebsd.org> To: Norbert Koch <nkoch@demig.de> Cc: freebsd-hackers@freebsd.org Subject: Re: bus device driver Message-ID: <200907140849.51702.jhb@freebsd.org> In-Reply-To: <4A5C2EF8.3080208@demig.de> References: <4A5B3F1B.3040207@demig.de> <200907131435.30452.jhb@freebsd.org> <4A5C2EF8.3080208@demig.de>
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On Tuesday 14 July 2009 3:08:40 am Norbert Koch wrote: >=20 > John Baldwin schrieb: > > On Monday 13 July 2009 10:05:15 am Norbert Koch wrote: > > =20 > >> Hello. > >> > >> I just started to write a device > >> driver for a multi-function pci card. > >> This card replaces a number of > >> independant isa hardware devices. > >> This pci card contains memory, i/o > >> and interrupt sources. > >> I want my device driver to > >> serve as a bus driver between > >> the pci driver and the specific > >> device drivers. > >> > >> Do I need more than the following (see below)? > >> Do I have to do any bookkeeping for allocated resources? > >> =20 > > > > How do the child devices receive resources? Do they suballocate region= s=20 from=20 > > BARs in the PCI device or is your device a subtractive bridge that will= =20 > > forward requests for ISA ranges and your devices all use ISA ranges? > > > > =20 > I am not quite sure that I understand what you mean. What is the differen= ce? > My old device drivers were isa based. We had all our resources in the=20 > 15-16M isa hole. > So I want to change them to just allocate resources from the pci bus=20 > through the bus device driver. > I thought it would be sufficient to just forward *_alloc_resource calls=20 > directly to the pci driver. > Clearly, my drivers will have to know that they are just forwarded=20 > through to pci > and have to know what sub-resources to allocate. =46rom a hardware perspective, how do your devices know which addresses to= =20 decode? Do they consume subranges of BARs or are they assigned fixed=20 addresses somehow? Do they have programmable decoders of some sort=20 themselves? If you wish to have the PCI bus assign you resources then that= =20 implies that your PCI device has a BAR and that you want to request resourc= es=20 for that BAR and then hand out subranges of that to your children. If that= =20 is the case, then you will need to allocate the resources for the BAR for t= he=20 PCI device from the PCI bus. Then your bus driver for the PCI device will= =20 need to suballoc from that BAR to your children devices. =2D-=20 John Baldwin
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