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SubjectRe: legacy VGA device requirements (was: Exposing ROM's though sysfs)
What should the API for this look like? We could add a VGA={0/1}
attribute to all the VGA devices in sysfs.

But then how do you:
1) list all of the conflicting VGA devices in a domain?
2) turn off all the VGA devices in a domain?

We could build a bus like directory structure in /sys/class


Then add an enable attribute in the domain directories that would shut
off all of the subdevices.


But the vga driver is not going to be attached to a device. Is there an
easy way to build this is sysfs?

--- Jesse Barnes <> wrote:

> On Tuesday, August 3, 2004 5:59 pm, Benjamin Herrenschmidt wrote:
> > All this could be very nicely dealt with by the kernel driver.
> So what requirements have we collected so far?
> o device selection (presumably domain, bus, slot, function)
> i.e. select the device you'd like to manipulate
> ioctl?
> o per-domain & device VGA enable/disable
> need to disable VGA ports on cards in the same domain and/or bus
> ioctl?
> o legacy port I/O
> for properly routing I/O in multi-domain machines and machines
> where the
> kernel or firmware may need to trap master aborts
> read/write?
> o legacy memory mapping
> for mapping the legacy VGA framebuffer, may fail
> mmap?
> Is that a complete list? Of course, the interface mechanisms are up
> for
> debate too. We might be able to do it with per-bus or per-domain
> files in
> sysfs for the legacy I/O and memory stuff, but that might not
> represent the
> fact that legacy devices have interdependencies very well (e.g. VGA
> ports
> must be disabled on device A before we poke device B, etc.).
> Thanks,
> Jesse

Jon Smirl

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