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author | David Herrmann <dh.herrmann@gmail.com> | 2014-01-03 14:09:47 +0100 |
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committer | David Herrmann <dh.herrmann@gmail.com> | 2014-03-16 12:17:03 +0100 |
commit | 31bbe16f6d88622d6731fa2cb4ab38d57d844ac1 (patch) | |
tree | 2a123ae13d3e3a9de36f82304b74b8052545cb87 /drivers/gpu/drm/qxl/qxl_ttm.c | |
parent | 786a7828bc74b9b1466e83abb200b75f80f94121 (diff) | |
download | linux-31bbe16f6d88622d6731fa2cb4ab38d57d844ac1.tar.bz2 |
drm: add pseudo filesystem for shared inodes
Our current DRM design uses a single address_space for all users of the
same DRM device. However, there is no way to create an anonymous
address_space without an underlying inode. Therefore, we wait for the
first ->open() callback on a registered char-dev and take-over the inode
of the char-dev. This worked well so far, but has several drawbacks:
- We screw with FS internals and rely on some non-obvious invariants like
inode->i_mapping being the same as inode->i_data for char-devs.
- We don't have any address_space prior to the first ->open() from
user-space. This leads to ugly fallback code and we cannot allocate
global objects early.
As pointed out by Al-Viro, fs/anon_inode.c is *not* supposed to be used by
drivers for anonymous inode-allocation. Therefore, this patch follows the
proposed alternative solution and adds a pseudo filesystem mount-point to
DRM. We can then allocate private inodes including a private address_space
for each DRM device at initialization time.
Note that we could use:
sysfs_get_inode(sysfs_mnt->mnt_sb, drm_device->dev->kobj.sd);
to get access to the underlying sysfs-inode of a "struct device" object.
However, most of this information is currently hidden and it's not clear
whether this address_space is suitable for driver access. Thus, unless
linux allows anonymous address_space objects or driver-core provides a
public inode per device, we're left with our own private internal mount
point.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Diffstat (limited to 'drivers/gpu/drm/qxl/qxl_ttm.c')
0 files changed, 0 insertions, 0 deletions