Messages in this thread | | | From | Jesse Barnes <> | Subject | Re: Exposing ROM's though sysfs | Date | Tue, 3 Aug 2004 19:16:01 -0700 |
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On Tuesday, August 3, 2004 6:57 pm, Benjamin Herrenschmidt wrote: > Jesse did a pretty good summary of what features need to be provided > though. Note also that this "arbitration" layer may also need an in-kernel > API for things like vgacon or whatever may want to "grab" access to the > VGA device.
Good point, I forgot about that. Theoretically, as long as a device has been POSTed, vgacon should work just fine with some small tweaks on platforms that allow mapping of the VGA framebuffer.
> I suggest that at this point, we don't try to bother with simultaneous > access to devices on separate PCI domains, but just use an in-kernel > semaphore to arbitrate the single user at a given point in time who "owns" > the VGA access, whatever bus it is on. So we need 2 things, both in-kernel > and for userland:
Sounds good. Cards usually POST pretty quickly, so that won't be a problem until someone puts 32 cards in a system (oh wait, that's not too far off :).
> - A way to identify a VGA device on a given bus. Could this be a PCI > ID (or in kernel a pci_dev ?). That would mean no support for non-PCI > stuffs, how bad would that be ?
I personally don't care about anything but PCI, AGP and PCI-Express, but you make a good point about embedded stuff.
> - Userland should use read/write for IOs imho, either to a /dev device > (with maybe an ioctl to switch between PIO and VGA mem, though mmap is > better for the later) or to some sysfs entry (in which case, can we add > mmap call to a sysfs attribute ? last time I looked, it wasn't simple).
Yeah, that sounds reasonable. I'd vote for a real device as opposed to sysfs files, for now at least.
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