No more read/write ioctls

[Ben Widawsky <ben@bwidawsk.net>]

On Fri, Apr 01, 2011 at 04:54:47PM -0700, Ben Widawsky wrote:

> So if this isn't okay by everyone, let's get down to the minimum number
> of changes required to get this accepted so I can move on to the tools,
> and then get back to the debug stuff.
> 

Some discussion on IRC has led to a new proposal (well 2 new proposals,
but the first one wasn't viable).

The interface will instead of using ioctls use debugfs. The debugfs file
will control force wake. There will be a refcount mechanism for number
of users of the registers in the relevant power-well, and upon opening a
specific file in debugfs (we could have one per power-well if needed),
the refcount will get incremented, and decremented at close.

In other words, for userspace to read/write registers:
fd = open(/sys/kernel/debug/dri...)
normal read write mechanism
close(fd)

There are two side effects which everyone on IRC seems fine with:
* root-only read access (the ioctl read was promiscuous)
* access is only available when debugfs is mounted

As a result, you should ignore both the gpu-tools patches, as well as
these kernel patches.

Thanks.
Ben