Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

I've failed to remember that we have virtual drivers like vgem which
have no underlying struct device. Fix this asap.
Reported-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Fixes: 5c484cee ("drm: Remove drm_driver->set_busid hook")
Cc: Thierry Reding <treding@nvidia.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170621130429.20537-1-daniel.vetter@ffwll.ch

I spotted a markup issue, plus adding the descriptions in drm_driver.
Plus a few more links while at it.

I'm still mildly unhappy with the split between fops and ioctls, but I
still think having the ioctls in the uapi chapter makes more sense. Oh
well ...

v2: Rebase.

v3: Move misplace hunk to the right patch.

Cc: Stefan Agner <stefan@agner.ch>
Acked-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170531092045.3950-1-daniel.vetter@ffwll.ch

The only special-case is pci devices, and we can easily handle this in
the core. Do so and drop a pile of boilerplate from drivers.
Acked-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170524145212.27837-5-daniel.vetter@ffwll.ch

I alwasy get confused about drm_wait_vblank for a split second until I
realize it's the ioctl handler. Unconfuse me, and do it for the legacy
modeset vblank control ioctl too.

While at it also noticed that I misplaced the irq ioctl handler in the
internal header file.
Acked-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170524145212.27837-12-daniel.vetter@ffwll.ch

Sync objects are new toplevel drm object, that contain a
pointer to a fence. This fence can be updated via command
submission ioctls via drivers.

There is also a generic wait obj API modelled on the vulkan
wait API (with code modelled on some amdgpu code).

These objects can be converted to an opaque fd that can be
passes between processes.

v2: rename reference/unreference to put/get (Chris)
fix leaked reference (David Zhou)
drop mutex in favour of cmpxchg (Chris)
v3: cleanups from danvet, rebase on drm_fops rename
check fd_flags is 0 in ioctls.
v4: export find/free, change replace fence to take a
syncobj. In order to support lookup first, replace
later semantics which seem in the end to be cleaner.
Reviewed-by: NSean Paul <seanpaul@chromium.org>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDave Airlie <airlied@redhat.com>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

drm_ioctl() guts sans copying the structure to/from userland
and parsing the ioctl cmd.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

With the atomic API, it is possible that a single commit affects
multiple crtcs. If the user requests an event with that commit, one
event will be sent for each CRTC, but it is not possible to distinguish
which crtc an event is for in user space. To solve this, the reserved
field in struct drm_vblank_event is repurposed to include the crtc_id
which the event is for.

The DRM_CAP_CRTC_IN_VBLANK_EVENT is added to allow userspace to query if
the crtc field will be set properly.

[daniels: Rebased, using Maarten's forward-port.]
Signed-off-by: NAnder Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Signed-off-by: NDaniel Stone <daniels@collabora.com>
Cc: Maarten Lankhorst <maarten.lankhorst@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170404165221.28240-2-daniels@collabora.com

Also unify/merge with the existing stuff.

I was a bit torn where to put this, but in the end I decided to put
all the ioctl/sysfs/debugfs stuff into drm-uapi.rst. That means we
have a bit a split with the other uapi related stuff used internally,
like drm_file.[hc], but I think overall this makes more sense.

If it's too confusing we can always add more cross-links to make it
more discoverable. But the auto-sprinkling of links kernel-doc already
does seems sufficient.

Also for prettier docs and more cross-links, switch the internal
defines over to an enum, as usual.

v2: Update kerneldoc fro drm_compat_ioctl too (caught by 0day), plus a
bit more drive-by polish.

v3: Fix typo, spotted by xerpi on irc (Sergi).

v4: Add missing space in comment (Neil).

Cc: Sergi Granell <xerpi.g.12@gmail.com>
Reviewed-by: NNeil Armstrong <narmstrong@baylibre.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170404095304.17599-4-daniel.vetter@ffwll.ch

To match the drm_ioctl.c we already have.

v2: Remove spurious space (Ville).

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

drm_ioctl_permit is exported but missed a kernel-doc style
documentation.
Signed-off-by: NGabriel Krisman Bertazi <krisman@collabora.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161228143216.26821-5-krisman@collabora.co.uk

Signed-off-by: NGabriel Krisman Bertazi <krisman@collabora.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161228143216.26821-4-krisman@collabora.co.uk

Spotted while auditing our ioctl table. Also nuke the
not-really-kerneldoc comments, we don't document internals and
definitely don't want to mislead people with the old dragons.

I think with this all the legacy ioctls now have proper drm_legacy_
prefixes.
Reviewed-by: NSean Paul <seanpaul@chromium.org>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161213230814.19598-2-daniel.vetter@ffwll.ch

With the last round of changes all ioctls called by modern drivers now
have their own locking. Everything else is only allowed for legacy
drivers and hence the lack of locking doesn't matter.

One exception is nouveau, due to the DRIVER_KMS_LEGACY_CONTEXT flag.
But that only works its magic on the context and bufs ioctls. And
drm_bufs.c is protected with dev->struct_mutex, and drm_context.c by
the same and dev->ctxlist_mutex. That should be all safe, and we can
finally mandata drm-bkl-less ioctls for everyone!
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161210215255.7765-3-daniel.vetter@ffwll.ch

It only updates per-file feature flags. And all the ioctl which change
behaviour depending upon these flags (they're all kms features) do
_not_ hold the BKL. Therefor this is pure cargo-cult and can be
removed.

Note that there's a risk that the ioctl will behave inconsistently
when userspace is racing with itself, but that's ok. The only thing
it's not allowed to do is oops the kernel, and from an audit all
places are safe.

v2: Clarify that the inconsistency is only when userspace races
(Chris).
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161210215255.7765-2-daniel.vetter@ffwll.ch

No one looks at the major/minor versions except the unique/busid
stuff. If we protect that with the master_mutex (since it also affects
the unique of each master, oh well) we can mark these two IOCTL with
DRM_UNLOCKED.

While doing this I realized that the comment for the magic_map is
outdated, I've forgotten to update it in:

commit d2b34ee6
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Fri Jun 17 09:33:21 2016 +0200

    drm: Protect authmagic with master_mutex

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NEmil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161210215255.7765-1-daniel.vetter@ffwll.ch

vgem (and our igt tests using vgem) need this. I suspect etnaviv will
fare similarly.

v2. Make it build. Oops.

Fixes: d5264ed3 ("drm: Return -ENOTSUPP when called for KMS cap with a non-KMS driver")
Cc: Michel Dänzer <michel.daenzer@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMichel Dänzer <michel.daenzer@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161207144939.22756-1-daniel.vetter@ffwll.ch

This is an attempt to make the previous fix a bit more robust going
forward.

v2:
* Only allow DRM_CAP_TIMESTAMP_MONOTONIC with UMS drivers (Daniel
  Vetter, Alex Deucher)
* Different logic to keep DRM_CAP_TIMESTAMP_MONOTONIC separate from
  the other caps (Daniel Vetter)
Signed-off-by: NMichel Dänzer <michel.daenzer@amd.com>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161201073731.5716-1-michel@daenzer.net

Fixes oops if userspace calls DRM_IOCTL_GET_CAP for
 DRM_CAP_PAGE_FLIP_TARGET on a non-KMS device node. (Normal userspace
doesn't do that, discovered by syzkaller)
Reported-by: NDmitry Vyukov <dvyukov@google.com>
Fixes: f837297a ("drm: Add DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE/RELATIVE flags v2")
Cc: stable@vger.kernel.org
Signed-off-by: NMichel Dänzer <michel.daenzer@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20161130083002.1520-1-michel@daenzer.net

The drm_core.h header contains a set of constants meant to be used
throughout DRM. However, as it turns out, they're each used just once and
don't bring any benefit. They're also grossly mis-named and lack
name-spacing. This patch inlines them, or moves them into drm_internal.h
as appropriate:

 - CORE_AUTHOR and CORE_DESC are inlined into corresponding MODULE_*()
   macros. It's just confusing having to follow 2 pointers when trying to
   find the definition of these fields. Grep'ping for MODULE_AUTHOR()
   should reveal the full information, if there's no strong reason not to.

 - CORE_NAME, CORE_DATE, CORE_MAJOR, CORE_MINOR, and CORE_PATCHLEVEL are
   inlined into the sysfs 'version' attribute. They're stripped
   everywhere else (which is just some printk() statements). CORE_NAME
   just doesn't make *any* sense, as we hard-code it in many places,
   anyway. The other constants are outdated and just serve
   binary-compatibility purposes. Hence, inline them in 'version' sysfs
   attribute (we might even try dropping it..).

 - DRM_IF_MAJOR and DRM_IF_MINOR are moved into drm_internal.h as they're
   only used by the global ioctl handlers. Furthermore, versioning
   interfaces breaks backports and as such is deprecated, anyway. We just
   keep them for historic reasons. I doubt anyone will ever modify them
   again.
Signed-off-by: NDavid Herrmann <dh.herrmann@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160901124837.680-6-dh.herrmann@gmail.com

The *only* known user of GETCLIENT is libva, which uses it to check
whether its own context is authenticated. It used to iterate all clients,
look for one that matches its own pid and then check its state.

The entire purpose for us to still have a GETCLIENT implementation is to
serve libva. So lets not pretend we do anything else: Make this function
return information on the caller's context only, fake the PID to the
caller's pid so they always match, and just fill in the "authenticated"
bit, nothing else.

This patch reduces the complexity of GETCLIENT to a bare minimum, avoids
any dependency on priv->uid or priv->pid (allows us to get rid of them),
and makes libva happy by always *exactly* returning the information it
wants.
Signed-off-by: NDavid Herrmann <dh.herrmann@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160825143505.7447-1-dh.herrmann@gmail.com

These flags allow userspace to explicitly specify the target vertical
blank period when a flip should take effect.

v2:
* Add new struct drm_mode_crtc_page_flip_target instead of modifying
  struct drm_mode_crtc_page_flip, to make sure all existing userspace
  code keeps compiling (Daniel Vetter)
Acked-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: NMichel Dänzer <michel.daenzer@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

Except for nouveau, only legacy drivers need this really. And nouveau
is already marked up with DRIVER_KMS_LEGACY_CONTEXT as the special
case.

I've tried to be careful to leave everything related to modeset still
using the DRIVER_MODESET flag. Otherwise it's a direct replacement of
!DRIVER_MODESET with DRIVER_LEGACY checks. Also helps readability
since fewer negative checks overall.
Reviewed-by: NDavid Herrmann <dh.herrmann@gmail.com>
Reviewed-by: NFrank Binns <frank.binns@imgtec.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470251470-30830-2-git-send-email-daniel.vetter@ffwll.ch

Currently, we completely ignore the user when it comes to the in/out
direction of the ioctl argument, as we simply cannot trust userspace.
(For example, they might request a copy of the modified ioctl argument
when the driver is not expecting such and so leak kernel stack.)
However, blindly copying over the target address may also lead to a
spurious EFAULT, and a failure after the ioctl was completed
successfully. This is important in order to avoid an ABI break when
extending an ioctl from IOR to IORW. Similar to how we only copy the
intersection of the kernel arg size and the user arg size, we only want
to copy back the kernel arg data iff both the kernel and userspace
request the copy.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1468335590-21023-1-git-send-email-chris@chris-wilson.co.uk

This patch fix a spelling typo found in
Documentation/DocBook/gpu/API-drm-ioctl-flags.html
It is because the html file was created from comments in source,
I have to fix the source.
Signed-off-by: NMasanari Iida <standby24x7@gmail.com>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160629234706.31209-1-standby24x7@gmail.com

Also extract drm_auth.h for nicer grouping.

v2: Nuke the other comments since they don't really explain a lot, and
within the drm core we generally only document functions exported to
drivers: The main audience for these docs are driver writers.

v3: Limit the exposure of drm_master internals by only including
drm_auth.h where it is neede (Chris).

v4: Spelling polish (Emil).

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NEmil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

Just rolling out a bit of abstraction to be able to clean
up the master logic in the next step.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NEmil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

We already have a fallback in place to fill out the unique from
dev->unique, which is set to something reasonable in drm_dev_alloc.

Which means we only need to have a special set_busid for pci devices,
to be able to care the backwards compat code for drm 1.1 around, which
libdrm still needs.

While developing and testing this patch things blew up in really
interesting ways, and the code is rather confusing in naming things
between the kernel code, ioctl #defines and libdrm. For the next brave
dragon slayer, document all this madness properly in the userspace
interface section of gpu.tmpl.

v2: Make drm_dev_set_unique static and update kerneldoc.

v3: Entire rewrite, plus document what's going on for posterity in the
gpu docbook uapi section.

v4: Drop accidental amdgpu hunk (Emil).

v5: Drop accidental omapdrm vblank counter change (Emil).

v6: Rebase on top of the sphinx conversion.

Cc: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Cc: Emil Velikov <emil.l.velikov@gmail.com>
Tested-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk> (virt_gpu)
Reviewed-by: NEmil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

Ever since

commit 2e1868b560315a8b20d688e646c489a5ad93eeae
Author: Eric Anholt <anholt@freebsd.org>
Date:   Wed Jun 16 09:25:21 2004 +0000

    DRI trunk-20040613 import

the X server supports drm 1.1, thus doesn't call call libdrm's
drmSetBusid - the sole user of this ioctl. When reviewing this note
that for hilarity both the kernel-internal functions (set_busid) and
the libdrm wrapper (drmSetBusid) have names not matching this ioctl
(SET_UNIQUE).

v2: Polish commit message (Emil).

Cc: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: NEmil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466499262-18717-6-git-send-email-daniel.vetter@ffwll.ch

Lots of arm drivers get this wrong and for most arm boards this is the
right thing actually. And anyway with most loaders you want to chase
sysfs links anyway to figure out which dri device you want.

This will fix dmesg noise for rockchip and sti.

Also add a fallback to driver->name for entirely virtual drivers like
vgem.

v2: Rebase on top of

commit e112e593
Author: Nicolas Iooss <nicolas.iooss_linux@m4x.org>
Date:   Fri Dec 11 11:20:28 2015 +0100

    drm: use dev_name as default unique name in drm_dev_alloc()

and simplify a bit. Plus add a comment.

v3: WARN_ON(!dev->unique) as discussed with Emil.

Cc: Ilia Mirkin <imirkin@alum.mit.edu>
Reported-by: NIlia Mirkin <imirkin@alum.mit.edu>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> (v2)
Reviewed-by: NEmil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466499262-18717-3-git-send-email-daniel.vetter@ffwll.ch

Again this is neatly protected by the dev->master_mutex now. There is
a driver callback both for set and drop, but it's only used by vmwgfx.
And vmwgfx has it's own solid locking for shared resources (besides
dev->master_mutex), hence is all safe. Let's drop another place where
the drm legacy bkl is used.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NEmil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466148814-8194-6-git-send-email-daniel.vetter@ffwll.ch

All protected by dev->master_mutex. And there's no driver callbacks,
which means no need to sync with old dri1 horror show drivers at all.
Hence safe to drop the drm legacy BKL from these paths.

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NEmil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466148814-8194-5-git-send-email-daniel.vetter@ffwll.ch

It belongs right next to the addmap and rmmap functions really. And
for OCD consistency name it drm_legacy_getmap_ioctl.
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NAlex Deucher <alexander.deucher@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461691808-12414-4-git-send-email-daniel.vetter@ffwll.ch

With the prep patches for i915 all kms drivers either have
DRM_UNLOCKED on all their ioctls. Or the ioctl always directly returns
with an invariant return value when in modeset mode. But that's only
the case for i915 and radeon. The drm core ioctls are unfortunately
too much a mess still to dare this.

Follow-up patches will remove DRM_UNLOCKED from all kms drivers to
prove that this is indeed the case.

Also update the documentation.

v2: Really only do this for driver ioctls, spotted by David Herrmann.
And drop spurious whitespace change.

Cc: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Reviewed-by: NDavid Herrmann <dh.herrmann@gmail.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

As usual pull it into the drm docbook template, too. And again as
usual I've decided to only document stuff exported to drivers, so all
the old leftover markup from the shared drm repo days lost the magic
** signature.
Reviewed-by: NDavid Herrmann <dh.herrmann@gmail.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

And use it in radeon to replace all the ioctls no longer valid in kms
mode. I plan to also use this later on when nuking the ums support for
i915.

Note that setting the function pointer in the ioctl table to NULL
would amount to the same, but that results in some debug output from
the drm_ioctl() function. I've figured it's cleaner to have a
special-purpose function.

Cc: Alex Deucher <alexdeucher@gmail.com>
Reviewed-by: NDavid Herrmann <dh.herrmann@gmail.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

We already express the drm/agp depencies correctly in Kconfig, so we
can rip this remnant from the shared drm core days.

Aside: Pretty much all the #ifdefs in radeon/nouveau could be killed
if ttm would provide dummy functions. I'm not going to volunteer for
that though.

v2: Use IS_ENABLED(CONFIG_AGP) as suggested by Ville

v3: Polish from Ville's review.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com> (v2)
Reviewed-by: NDavid Herrmann <dh.herrmann@gmail.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>