Add updating entry for DRM

Update messaging for which drm module to install. Add guidance on what
hardware is supported (which should be copied into the release
notes). Note: the in tree drivers are abandonware. There has been no
organized support for them for many years, and the plan is to still
remove them for all but arm once the transition to drm-*kmod is
complete. Also note that WITHOUT_MODULE_DRM and WITHOUT_MODULE_DRM2
should generally be added to src.conf for anybody using the drm-*kmod
ports. That will become default in 13 soon, however.

Approved by: FreeBSD Graphics Team
Relnotes: Yes
MFC After: 3 days
Differential Revision: https://reviews.freebsd.org/D17451

UPDATING

@@ -31,6 +31,31 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 13.x IS SLOW:
 	disable the most expensive debugging functionality run
 	"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
 
+20181015:
+	Ports for the DRM modules have been simplified. Now, amd64 users should
+	just install the drm-kmod port. All others should install
+	drm-legacy-kmod.
+
+	Graphics hardware that's newer than about 2010 usually works with
+	drm-kmod.  For hardware older than 2013, however, some users will need
+	to use drm-legacy-kmod if drm-kmod doesn't work for them. Hardware older
+	than 2008 usually only works in drm-legacy-kmod. The graphics team can
+	only commit to hardware made since 2013 due to the complexity of the
+	market and difficulty to test all the older cards effectively. If you
+	have hardware supported by drm-kmod, you are strongly encouraged to use
+	that as you will get better support.
+
+	Other than KPI chasing, drm-legacy-kmod will not be updated. As outlined
+	elsewhere, the drm and drm2 modules will be eliminated from the src base
+	soon (with a limited exception for arm). Please update to the package asap
+	and report any issues to x11@freebsd.org.
+
+	Generally, anybody using the drm*-kmod packages should add
+	WITHOUT_DRM_MODULE=t and WITHOUT_DRM2_MODULE=t to avoid nasty
+	cross-threading surprises, especially with automatic driver
+	loading from X11 startup. These will become the defaults in 13-current
+	shortly.
+
 20181009:
 	OpenSSL has been updated to version 1.1.1.  This update included
 	additional various API changes througout the base system.  It is

sys/dev/drm2/drm_os_freebsd.h

@@ -154,8 +154,8 @@ typedef void			irqreturn_t;
 	*(volatile u_int64_t *)(((vm_offset_t)(map)->handle) +		\
 	    (vm_offset_t)(offset)) = htole64(val)
 
-#ifdef __LP64__
-#define DRM_PORT "graphics/drm-stable-kmod"
+#ifdef amd64
+#define DRM_PORT "graphics/drm-kmod"
 #else
 #define DRM_PORT "graphics/drm-legacy-kmod"
 #endif