From 31bbe16f6d88622d6731fa2cb4ab38d57d844ac1 Mon Sep 17 00:00:00 2001 From: David Herrmann Date: Fri, 3 Jan 2014 14:09:47 +0100 Subject: 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 Signed-off-by: David Herrmann --- fs/dcache.c | 1 + 1 file changed, 1 insertion(+) (limited to 'fs') diff --git a/fs/dcache.c b/fs/dcache.c index 265e0ce9769c..66dc62cb766d 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -3112,6 +3112,7 @@ char *simple_dname(struct dentry *dentry, char *buffer, int buflen) end = ERR_PTR(-ENAMETOOLONG); return end; } +EXPORT_SYMBOL(simple_dname); /* * Write full pathname from the root of the filesystem into the buffer. -- cgit v1.2.3