Date: Wed, 13 Feb 2013 16:21:49 -0700 From: Warner Losh <imp@bsdimp.com> To: Marcel Moolenaar <marcel@xcllnt.net> Cc: "freebsd-arch@FreeBSD.org Arch" <freebsd-arch@freebsd.org> Subject: Re: FDT on x86 and for non-fdtbus devices. Message-ID: <77486082-2D96-49CC-9841-2D1572F86DEE@bsdimp.com> In-Reply-To: <03A622DA-EFD4-4984-8FC3-CD8B4832C32E@xcllnt.net> References: <03A622DA-EFD4-4984-8FC3-CD8B4832C32E@xcllnt.net>
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On Feb 13, 2013, at 1:56 PM, Marcel Moolenaar wrote: > All, >=20 > Here at Juniper we added support for FDT to x86 (we'll contribute > that shortly). However, it's applicability is rather limited right > now by virtue of needing the devices to be attached to fdtbus > (directly or indirectly). That's cool... > This so that we can map from device_t > to pnode_t. However, there's great value in being able to use the > FDT to tweak the behaviour of any device in the system, and in > particular when we don't need nor use FDT to enumerate them. Yes, I can see that for many possible cases... However, you'll have to = solve the namespace boundary problems inherent in such an undertaking... > What we like to do is to use the FDT to define properties for > pretty much any kind of device. Examples are: > 1. Allow the FDT to define the name by which an interface is > to be created. This might be hard... Perhaps you could flesh out a bit how you'd = propose to do this. > 2. Enumerate smb devices so that we can attach drivers for them > under smbus when we don't need FDT to find ichsmb itself. If there's a 1-1 correspondence in the the FDT between the smb bridge = driver (ichsmb) and the sub devices, this could work. > I think one way to state the problem in a generic way is: How > can we obtain the FDT pnode_t given an arbitrary device_t and > use the pnode_t to query for properties, etc. Yes. What's the naming conventions we need to use here, especially since = names in the FDT don't necessarily match our driver names. Crazy idea: = define freebsd,driver-name properlty to make this association explicit. > Are people already doing things like this? only a little. > Is there an interest in being able to do things like this? Yes. > Are changes to drivers to have them query FDT contributable at > all or do people think such would be "pollution"? I like this idea, but others may not be so open to it. > Thoughts? > Ideas? "Go speed racer! Go!" Warner=
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