Quick Summary
- Add struct module * owner field to struct device_driver
- Change {get,put}_driver to use it
- Add void * object to struct driver_file_entry that points to owner of
file.
- Add struct driverfs_subsys with {get,put}_object callbacks to do generic
reference counting on file open/release
- Convert driverfs interface to struct devices to use above mechnanism
- Add 'bindings' between struct device_driver and struct bus_type, using
above mechanism to do proper reference counting on objects.
Pull from bk://ldm.bkbits.net/linux-2.5-driverfs
Patch also available from:
http://kernel.org/pub/linux/kernel/people/mochel/patches/driverfs-patch-08072002.gz
Changelog and diffstat appended.
Explanation:
driverfs currently does reference counting on struct device on file open()
and release(). It accesses the device by doing a list_entry on the
parent directory entry of the driver_file_entry (which is in the inode's
u.generic_ip).
This works fine, but is not very extensible to other objects that we want
to export files for, like struct device_driver. One way to do it is create
separate open/release callbacks for each object type that does a similar
list_entry. But, I considered that bulky and instead genericized a sole
pair of open and release calls.
To make it work for all objects, I added
void * object;
to struct driver_file_entry, and created
struct driverfs_subsys {
int (*get_object)(void * obj);
void (*put_object)(void * obj);
};
and
struct driverfs_subsys * subsys;
in struct driver_dir_entry to do reference counting on that object.
Wait, come back; it should work.
Each type of object that is represented in driverfs gets a directory that
is created when registered with the subsystem they belong to. When this
directory is created, the subsystem is responsible for setting the
subsys pointer in the directory entry.
To create files, there should be wrapper functions for each type of object
that take an explicit pointer to that object. E.g.
device_create_file
driver_create_file
etc.
The subsystem is responsibile for setting the object pointer on file
creation.
During open(), we get the driver_file_entry from the inode's u.generic_ip.
>From that, we get the parent driver_dir_entry and the subsys structure. We
pass the driver_file_entry::object to the subsys's get_object() callback.
The subsystem pins the object in memory, and life is a bit happier.
On release, we do the same in order to call put_object().
Having get/set functions that take opaque pointers can appear to
completely sacrifice type-safety. However, the fact that the only thing we
have to work with initially is an opaque pointer in u.generic_ip makes
that point, IMHO.
Plus, the driverfs code never relies on the validity of that pointer. It
simply passes it back to the subsystem to verify it and refcount. It's the
sole responsibility of the subsystem to not do something stupid.
It is possible to change the contents of the object pointer, the
driver_file_entry, or the inode after the file has been created. But, if
you aim the gun at your foot, and your finger slips off the trigger, it's
not my fault...
Anyway, it is now really easy to extend driverfs to support any type of
object. To add 'bindings' for a particular object type, it is literally
about 45 lines (excluding comments). See drivers/base/fs/*.c for examples.
Concerning reference counting on objects that aren't devices; i.e.
drivers: Drivers can be modular, and the refcount wasn't tied to the
module refcount. I went around a few times with Kai about this, about a
month ago. What I ended doing was adding an owner field to the
device_driver structure, and using that to do refcounting.
During normal operation, the refcount stays at 0, so the module can be
removed. During any access to the driver, it bumps up the refcount. (This
likely still suffers from the same module race conditions, but it's a step
in the right direction.)
I've also updated the driverfs documentation to reflect the recent changes
and removed most gross inaccuracies.
-pat
ChangeSet@1.447.23.1, 2002-06-10 09:12:20-07:00, mochel@osdl.org
driver refcounting:
Make {get,put}_driver simply wrappers for touching module reference count
Get rid of driver's release callback
Rename remove_driver to driver_unregister
diffstat results:
drivers/base/driver.c | 53 +++++++++++++++++++++++------------------------
drivers/pci/pci-driver.c | 2 -
include/linux/device.h | 14 ++----------
3 files changed, 31 insertions, 38 deletions
ChangeSet@1.604.3.13, 2002-07-03 13:40:09-07:00, mochel@osdl.org
Don't set module owner in driver_register, that's just dumb. Drivers need to do it explicitly.
diffstat results:
drivers/base/driver.c | 1 -
1 files changed, 1 deletion
ChangeSet@1.604.3.14, 2002-07-03 13:59:55-07:00, mochel@osdl.org
driverfs: Break out file creation functions from inode.c into lib.c
diffstat results:
fs/driverfs/Makefile | 4
fs/driverfs/inode.c | 278 -------------------------------------------------
fs/driverfs/lib.c | 289 +++++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 292 insertions, 279 deletions
ChangeSet@1.604.3.15, 2002-07-03 14:21:45-07:00, mochel@osdl.org
driverfs:
- typedef show and store callbacks in driver_file_entry
- Add an object pointer that points to the object that owns the file
diffstat results:
include/linux/driverfs_fs.h | 9 +++++++--
1 files changed, 7 insertions, 2 deletions
ChangeSet@1.604.3.16, 2002-07-03 14:22:41-07:00, mochel@osdl.org
driverfs file creation for devices:
Set the object pointer in the struct driver_file_entry when creating a file for the device
diffstat results:
drivers/base/fs.c | 2 ++
1 files changed, 2 insertions
ChangeSet@1.604.3.17, 2002-07-03 14:24:04-07:00, mochel@osdl.org
driverfs:
- Use the object field of struct driver_file_entry when calling the owner's show and store callbacks
- Use the object field on open and release, instead of using list_entry
diffstat results:
fs/driverfs/inode.c | 14 ++++----------
1 files changed, 4 insertions, 10 deletions
ChangeSet@1.604.3.18, 2002-07-03 15:31:56-07:00, mochel@osdl.org
driverfs:
- add driverfs_subsys to describe a subsystem that owns a class of objects that are represented in driverfs
Previously, all directories in driverfs mapped to struct device's. This assumption was used to do reference
counting on the devices. They were also passed to the show and store callbacks of the file owners.
However, now we want to be able to add files for other types of objects. We want to do reference counting on these
objects, and pass them downstream. The show and store callbacks were modified to take void *, instead of creating
a different type of show and store for each type of object that can have files.
Reference counting takes place in file open and release. Instead of defining a completely separate open and release
for each subsystem or type of object, I've implemented only what we need - callbacks to increment and decrement
the reference count of the target objects.
It's assumed that each object that has presence in driverfs has a directory. When this directory is created (by the
subsystem that owns it), it the subsys field needs to be set appropriately.
diffstat results:
include/linux/driverfs_fs.h | 6 ++++++
1 files changed, 6 insertions
ChangeSet@1.604.3.19, 2002-07-03 15:37:54-07:00, mochel@osdl.org
driverfs:
Use the driverfs_subsys types in open and release to do reference counting on the object that owns the file
It tries to be stringent about the whole situation:
- Return an error if
- no subsys is present
- get_object() fails (returns 0)
- Don't return error if
- get_object() isn't implemented (no ref counting on objects)
- get_object() returns 1
On release, it's assumed the subsys pointer is valid, since we wouldn't have allowed file open if it wasn't.
diffstat results:
fs/driverfs/inode.c | 31 ++++++++++++++++++++++---------
1 files changed, 22 insertions, 9 deletions
ChangeSet@1.604.3.20, 2002-07-03 15:39:08-07:00, mochel@osdl.org
device <-> driverfs interface:
Declare a driverfs_device_subsys, complete with get_object and put_object callbacks
Set the pointer in device's directory entry when their directory is created
diffstat results:
drivers/base/fs.c | 18 ++++++++++++++++++
1 files changed, 18 insertions
ChangeSet@1.604.3.21, 2002-07-03 16:58:18-07:00, mochel@osdl.org
device model:
Move driverfs interface (fs.c) to drivers/base/fs/
diffstat results:
drivers/base/fs.c | 217 -----------------------------------------------
drivers/base/Makefile | 4
drivers/base/fs/Makefile | 5 +
drivers/base/fs/fs.c | 217 +++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 225 insertions, 218 deletions
ChangeSet@1.604.3.22, 2002-07-03 17:04:29-07:00, mochel@osdl.org
device model - driverfs bindings:
Move device <-> driverfs binding to separate file; pave way for new bindings to come
diffstat results:
drivers/base/fs/Makefile | 4 -
drivers/base/fs/device.c | 127 +++++++++++++++++++++++++++++++++++++++++++++++
drivers/base/fs/fs.c | 116 ------------------------------------------
drivers/base/fs/fs.h | 5 +
4 files changed, 134 insertions, 118 deletions
ChangeSet@1.604.3.23, 2002-07-03 17:42:02-07:00, mochel@osdl.org
device model:
- move driverfs <-> bus bindings into drivers/base/fs/bus.c
- add helpers to create/remove files for buses
diffstat results:
drivers/base/base.h | 3 +
drivers/base/bus.c | 38 -----------------
drivers/base/fs/Makefile | 4 -
drivers/base/fs/bus.c | 105 +++++++++++++++++++++++++++++++++++++++++++++++
4 files changed, 111 insertions, 39 deletions
ChangeSet@1.604.3.24, 2002-07-03 17:54:20-07:00, mochel@osdl.org
device model driverfs bindings:
Implement device_dup_file for use by various specific bindings:
- allocate new driver_file_entry
- copy template in
- create driverfs file
- return error to caller
diffstat results:
drivers/base/fs/bus.c | 22 +++++-----------------
drivers/base/fs/device.c | 24 ++++++------------------
drivers/base/fs/fs.c | 18 ++++++++++++++++++
drivers/base/fs/fs.h | 2 ++
4 files changed, 31 insertions, 35 deletions
ChangeSet@1.604.3.25, 2002-07-05 13:55:01-07:00, mochel@osdl.org
device model <-> driverfs bindings
Rename device_dup_file to common_create_file
Make it inc/dec reference count on object that's passed in
Add common_remove_file that touches reference count of object and calls driverfs to remove file
diffstat results:
drivers/base/fs/fs.c | 35 +++++++++++++++++++++++++----------
drivers/base/fs/fs.h | 3 ++-
2 files changed, 27 insertions, 11 deletions
ChangeSet@1.604.3.26, 2002-07-05 13:57:30-07:00, mochel@osdl.org
Add device driver <-> driverfs bindings
diffstat results:
drivers/base/base.h | 3 ++
drivers/base/driver.c | 10 -------
drivers/base/fs/driver.c | 60 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 63 insertions, 10 deletions
ChangeSet@1.604.3.27, 2002-07-05 13:58:13-07:00, mochel@osdl.org
add driver.o target in drivers/base/fs/
diffstat results:
drivers/base/fs/Makefile | 4 ++--
1 files changed, 2 insertions, 2 deletions
ChangeSet@1.604.3.28, 2002-07-05 13:59:26-07:00, mochel@osdl.org
device model, bus drivers
Convert bus_create_file to use common_create_file and bus_remove_file to use common_remove_file (and let them handle reference counting)
Export bus_{create,remove}_file
diffstat results:
drivers/base/fs/bus.c | 19 +++++--------------
1 files changed, 5 insertions, 14 deletions
ChangeSet@1.604.3.29, 2002-07-05 14:00:42-07:00, mochel@osdl.org
Convert device_{create,remove}_file to use common_{create,remove}_file
diffstat results:
drivers/base/fs/device.c | 24 +++++++-----------------
1 files changed, 7 insertions, 17 deletions
ChangeSet@1.604.3.30, 2002-07-05 14:01:40-07:00, mochel@osdl.org
Add prototypes for {bus,driver}_{create,remove}_file to include/linux/device.h
diffstat results:
include/linux/device.h | 8 ++++++++
1 files changed, 8 insertions
ChangeSet@1.604.3.31, 2002-07-05 15:54:13-07:00, mochel@osdl.org
Rewrite driverfs documentation
diffstat results:
Documentation/filesystems/driverfs.txt | 366 ++++++++++++++++++++++-----------
1 files changed, 251 insertions, 115 deletions
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This archive was generated by hypermail 2b29 : Mon Jul 15 2002 - 22:00:13 EST