suspend/resume
The goal is to avoid that the vt(4) resume happens before the video
display is resumed. The original patch was provided by Andriy Gapon.
This new patch registers the handlers in vt_upgrade(). This is done
once, thanks to the VDF_ASYNC flag. I abused this flag because it was
already abused by the keyboard allocation. The event handlers then call
the backend if it provides callbacks for suspend/resume.
Differential Revision: https://reviews.freebsd.org/D1004
On behalf of: dumbbell
MFC after: 2 weeks
vt_fb_attach() currently always returns 0, but it could return a code
defined in errno.h. However, it doesn't return a CN_* code. So checking
its return value against CN_DEAD (which is 0) is incorrect, and in this
case, a success becomes a failure.
The consequence was unimportant, because the caller (drm_fb_helper.c)
would only log an error message in this case. The console would still
work.
Approved by: nwhitehorn
rather than only drivers attached later on. This involves a small amount of
code duplication with dev/fb/fbd.c, which will fixed later on.
Also improve performance of vt_blank() by making it not read from the
framebuffer unnecessarily.
o Forward termianl framebuffer ioctl to fbd.
o Forward terminal mmap request to fbd.
o Move inclusion of sys/conf.h to vt.h.
Sponsored by: The FreeBSD Foundation
