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2017-03-21chardev: add helper function to register char devs with a struct deviceLogan Gunthorpe
Credit for this patch goes is shared with Dan Williams [1]. I've taken things one step further to make the helper function more useful and clean up calling code. There's a common pattern in the kernel whereby a struct cdev is placed in a structure along side a struct device which manages the life-cycle of both. In the naive approach, the reference counting is broken and the struct device can free everything before the chardev code is entirely released. Many developers have solved this problem by linking the internal kobjs in this fashion: cdev.kobj.parent = &parent_dev.kobj; The cdev code explicitly gets and puts a reference to it's kobj parent. So this seems like it was intended to be used this way. Dmitrty Torokhov first put this in place in 2012 with this commit: 2f0157f char_dev: pin parent kobject and the first instance of the fix was then done in the input subsystem in the following commit: 4a215aa Input: fix use-after-free introduced with dynamic minor changes Subsequently over the years, however, this issue seems to have tripped up multiple developers independently. For example, see these commits: 0d5b7da iio: Prevent race between IIO chardev opening and IIO device (by Lars-Peter Clausen in 2013) ba0ef85 tpm: Fix initialization of the cdev (by Jason Gunthorpe in 2015) 5b28dde [media] media: fix use-after-free in cdev_put() when app exits after driver unbind (by Shauh Khan in 2016) This technique is similarly done in at least 15 places within the kernel and probably should have been done so in another, at least, 5 places. The kobj line also looks very suspect in that one would not expect drivers to have to mess with kobject internals in this way. Even highly experienced kernel developers can be surprised by this code, as seen in [2]. To help alleviate this situation, and hopefully prevent future wasted effort on this problem, this patch introduces a helper function to register a char device along with its parent struct device. This creates a more regular API for tying a char device to its parent without the developer having to set members in the underlying kobject. This patch introduce cdev_device_add and cdev_device_del which replaces a common pattern including setting the kobj parent, calling cdev_add and then calling device_add. It also introduces cdev_set_parent for the few cases that set the kobject parent without using device_add. [1] https://lkml.org/lkml/2017/2/13/700 [2] https://lkml.org/lkml/2017/2/10/370 Signed-off-by: Logan Gunthorpe <logang@deltatee.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com> Reviewed-by: Hans Verkuil <hans.verkuil@cisco.com> Reviewed-by: Alexandre Belloni <alexandre.belloni@free-electrons.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2015-01-20fs: introduce f_op->mmap_capabilities for nommu mmap supportChristoph Hellwig
Since "BDI: Provide backing device capability information [try #3]" the backing_dev_info structure also provides flags for the kind of mmap operation available in a nommu environment, which is entirely unrelated to it's original purpose. Introduce a new nommu-only file operation to provide this information to the nommu mmap code instead. Splitting this from the backing_dev_info structure allows to remove lots of backing_dev_info instance that aren't otherwise needed, and entirely gets rid of the concept of providing a backing_dev_info for a character device. It also removes the need for the mtd_inodefs filesystem. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Tejun Heo <tj@kernel.org> Acked-by: Brian Norris <computersforpeace@gmail.com> Signed-off-by: Jens Axboe <axboe@fb.com>
2011-01-13fs/char_dev.c: remove unused cdev_index()Namhyung Kim
Commit 66fa12c571d3 ("ieee1394: remove the old IEEE 1394 driver stack") eliminated the only user of cdev_index(). So it can be removed too. Signed-off-by: Namhyung Kim <namhyung@gmail.com> Cc: Stefan Richter <stefanr@s5r6.in-berlin.de> Cc: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2009-06-11fs: Remove i_cindex from struct inodeTheodore Ts'o
The only user of the i_cindex element in the inode structure is used is by the firewire drivers. As part of an attempt to slim down the inode structure to save memory --- since a typical Linux system will have hundreds of thousands if not millions of inodes cached, a reduction in the size inode has high leverage. The firewire driver does not need i_cindex in any fast path, so it's simple enough to calculate when it is needed, instead of wasting space in the inode structure. Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: krh@redhat.com Cc: stefanr@s5r6.in-berlin.de Cc: linux-fsdevel@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2008-04-30Remove "#ifdef __KERNEL__" checks from unexported headersRobert P. J. Day
Remove the "#ifdef __KERNEL__" tests from unexported header files in linux/include whose entire contents are wrapped in that preprocessor test. Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Sam Ravnborg <sam@ravnborg.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-01-30[PATCH] cdev.h: forward declarationsJan Engelhardt
Apparently this broke due to missing `struct inode' declaration. Signed-off-by: Jan Engelhardt <jengelh@gmx.de> Cc: Noah Watkins <nwatkins@ittc.ku.edu> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2006-12-07[PATCH] pull in necessary header files for cdev.hJan Engelhardt
linux/cdev.h uses struct kobject and other structs and should therefore include them. Currently, a module either needs to add the missing includes itself, or, in case a module includes other headers already, needs to put <linux/cdev.h> last, which goes against a alphabetically-sorted include list. Signed-off-by: Jan Engelhardt <jengelh@gmx.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-09-27[PATCH] NOMMU: Set BDI capabilities for /dev/mem and /dev/kmemDavid Howells
Set the backing device info capabilities for /dev/mem and /dev/kmem to permit direct sharing under no-MMU conditions and full mapping capabilities under MMU conditions. Make the BDI used by these available to all directly mappable character devices. Also comment the capabilities for /dev/zero. [akpm@osdl.org: ifdef reductions] Signed-off-by: David Howells <dhowells@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-28[PATCH] mark f_ops const in the inodeArjan van de Ven
Mark the f_ops members of inodes as const, as well as fix the ripple-through this causes by places that copy this f_ops and then "do stuff" with it. Signed-off-by: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-04-16Linux-2.6.12-rc2Linus Torvalds
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!