Date: Wed, 21 Jan 2009 08:47:05 -0500 From: John Baldwin <jhb@freebsd.org> To: freebsd-arch@freebsd.org Cc: Andre Albsmeier <Andre.Albsmeier@siemens.com> Subject: Re: Two drivers, one physical device: How to deal with that? Message-ID: <200901210847.05858.jhb@freebsd.org> In-Reply-To: <20081229143221.X1076@desktop> References: <20081229212020.GA1809@curry.mchp.siemens.de> <20081229143221.X1076@desktop>
next in thread | previous in thread | raw e-mail | index | archive | help
On Monday 29 December 2008 7:35:21 pm Jeff Roberson wrote: > On Mon, 29 Dec 2008, Andre Albsmeier wrote: > > > Hello, > > > > I have written a driver which attaches to the host bridge in > > order to periodically read the appropriate registers and > > inform the user about ECC errors (ECC-Monitor). No I have > > run across a mainboard where the host bridge is already > > taken by the agp driver. Of course, I can detach the agp > > driver and attach myself and everything is working but > > what is if someone does not want to loose the agp > > functionality? > > > > How does one deal with the case when two separate drivers > > have to access the same device (the host bridge in my case)? > > > > I assume, the correct way would be to join the AGP and > > ECC functionality in one driver but maybe there are other > > tricks I am not aware of? > > Well I don't think it would be correct to merge two conceptually seperate > drivers into one just to share the same device. It sounds like the right > solution is to make a generic layer the attaches to the host bridge and > arbitrates access to it. Then allow other device to find and communicate > with this generic layer. For the host bridge this doesn't have to be > particularly fancy. This is already the case in 7.0 and later where hostb(4) always attaches to host bridges and agp(4) attaches to the hostb(4) devices. -- John Baldwin
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200901210847.05858.jhb>