• David Herrmann's avatar
    drm: provide device-refcount · 099d1c29
    David Herrmann authored
    Lets not trick ourselves into thinking "drm_device" objects are not
    ref-counted. That's just utterly stupid. We manage "drm_minor" objects on
    each drm-device and each minor can have an unlimited number of open
    handles. Each of these handles has the drm_minor (and thus the drm_device)
    as private-data in the file-handle. Therefore, we may not destroy
    "drm_device" until all these handles are closed.
    
    It is *not* possible to reset all these pointers atomically and restrict
    access to them, and this is *not* how this is done! Instead, we use
    ref-counts to make sure the object is valid and not freed.
    
    Note that we currently use "dev->open_count" for that, which is *exactly*
    the same as a reference-count, just open coded. So this patch doesn't
    change any semantics on DRM devices (well, this patch just introduces the
    ref-count, anyway. Follow-up patches will replace open_count by it).
    
    Also note that generic VFS revoke support could allow us to drop this
    ref-count again. We could then just synchronously disable any fops->xy()
    calls. However, this is not the case, yet, and no such patches are
    in sight (and I seriously question the idea of dropping the ref-cnt
    again).
    Signed-off-by: default avatarDavid Herrmann <dh.herrmann@gmail.com>
    099d1c29
drm_usb.c 1.63 KB