Merge branch 'topic/soundcore-preclaim' into for-linus

* topic/soundcore-preclaim:
  sound: make OSS device number claiming optional and schedule its removal
  sound: request char-major-* module aliases for missing OSS devices
  chrdev: implement __[un]register_chrdev()
This commit is contained in:
Takashi Iwai 2009-09-10 15:33:04 +02:00
commit 3827119e20
5 changed files with 176 additions and 34 deletions

View file

@ -468,3 +468,27 @@ Why: cpu_policy_rwsem has a new cleaner definition making it local to
cpufreq core and contained inside cpufreq.c. Other dependent
drivers should not use it in order to safely avoid lockdep issues.
Who: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
----------------------------
What: sound-slot/service-* module aliases and related clutters in
sound/sound_core.c
When: August 2010
Why: OSS sound_core grabs all legacy minors (0-255) of SOUND_MAJOR
(14) and requests modules using custom sound-slot/service-*
module aliases. The only benefit of doing this is allowing
use of custom module aliases which might as well be considered
a bug at this point. This preemptive claiming prevents
alternative OSS implementations.
Till the feature is removed, the kernel will be requesting
both sound-slot/service-* and the standard char-major-* module
aliases and allow turning off the pre-claiming selectively via
CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss
kernel parameter.
After the transition phase is complete, both the custom module
aliases and switches to disable it will go away. This removal
will also allow making ALSA OSS emulation independent of
sound_core. The dependency will be broken then too.
Who: Tejun Heo <tj@kernel.org>

View file

@ -237,8 +237,10 @@ int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
}
/**
* register_chrdev() - Register a major number for character devices.
* __register_chrdev() - create and register a cdev occupying a range of minors
* @major: major device number or 0 for dynamic allocation
* @baseminor: first of the requested range of minor numbers
* @count: the number of minor numbers required
* @name: name of this range of devices
* @fops: file operations associated with this devices
*
@ -254,19 +256,17 @@ int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
* /dev. It only helps to keep track of the different owners of devices. If
* your module name has only one type of devices it's ok to use e.g. the name
* of the module here.
*
* This function registers a range of 256 minor numbers. The first minor number
* is 0.
*/
int register_chrdev(unsigned int major, const char *name,
const struct file_operations *fops)
int __register_chrdev(unsigned int major, unsigned int baseminor,
unsigned int count, const char *name,
const struct file_operations *fops)
{
struct char_device_struct *cd;
struct cdev *cdev;
char *s;
int err = -ENOMEM;
cd = __register_chrdev_region(major, 0, 256, name);
cd = __register_chrdev_region(major, baseminor, count, name);
if (IS_ERR(cd))
return PTR_ERR(cd);
@ -280,7 +280,7 @@ int register_chrdev(unsigned int major, const char *name,
for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
*s = '!';
err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
err = cdev_add(cdev, MKDEV(cd->major, baseminor), count);
if (err)
goto out;
@ -290,7 +290,7 @@ int register_chrdev(unsigned int major, const char *name,
out:
kobject_put(&cdev->kobj);
out2:
kfree(__unregister_chrdev_region(cd->major, 0, 256));
kfree(__unregister_chrdev_region(cd->major, baseminor, count));
return err;
}
@ -316,10 +316,23 @@ void unregister_chrdev_region(dev_t from, unsigned count)
}
}
void unregister_chrdev(unsigned int major, const char *name)
/**
* __unregister_chrdev - unregister and destroy a cdev
* @major: major device number
* @baseminor: first of the range of minor numbers
* @count: the number of minor numbers this cdev is occupying
* @name: name of this range of devices
*
* Unregister and destroy the cdev occupying the region described by
* @major, @baseminor and @count. This function undoes what
* __register_chrdev() did.
*/
void __unregister_chrdev(unsigned int major, unsigned int baseminor,
unsigned int count, const char *name)
{
struct char_device_struct *cd;
cd = __unregister_chrdev_region(major, 0, 256);
cd = __unregister_chrdev_region(major, baseminor, count);
if (cd && cd->cdev)
cdev_del(cd->cdev);
kfree(cd);
@ -568,6 +581,6 @@ EXPORT_SYMBOL(cdev_alloc);
EXPORT_SYMBOL(cdev_del);
EXPORT_SYMBOL(cdev_add);
EXPORT_SYMBOL(cdev_index);
EXPORT_SYMBOL(register_chrdev);
EXPORT_SYMBOL(unregister_chrdev);
EXPORT_SYMBOL(__register_chrdev);
EXPORT_SYMBOL(__unregister_chrdev);
EXPORT_SYMBOL(directly_mappable_cdev_bdi);

View file

@ -1998,12 +1998,25 @@ extern void bd_release_from_disk(struct block_device *, struct gendisk *);
#define CHRDEV_MAJOR_HASH_SIZE 255
extern int alloc_chrdev_region(dev_t *, unsigned, unsigned, const char *);
extern int register_chrdev_region(dev_t, unsigned, const char *);
extern int register_chrdev(unsigned int, const char *,
const struct file_operations *);
extern void unregister_chrdev(unsigned int, const char *);
extern int __register_chrdev(unsigned int major, unsigned int baseminor,
unsigned int count, const char *name,
const struct file_operations *fops);
extern void __unregister_chrdev(unsigned int major, unsigned int baseminor,
unsigned int count, const char *name);
extern void unregister_chrdev_region(dev_t, unsigned);
extern void chrdev_show(struct seq_file *,off_t);
static inline int register_chrdev(unsigned int major, const char *name,
const struct file_operations *fops)
{
return __register_chrdev(major, 0, 256, name, fops);
}
static inline void unregister_chrdev(unsigned int major, const char *name)
{
__unregister_chrdev(major, 0, 256, name);
}
/* fs/block_dev.c */
#define BDEVNAME_SIZE 32 /* Largest string for a blockdev identifier */
#define BDEVT_SIZE 10 /* Largest string for MAJ:MIN for blkdev */

View file

@ -32,6 +32,34 @@ config SOUND_OSS_CORE
bool
default n
config SOUND_OSS_CORE_PRECLAIM
bool "Preclaim OSS device numbers"
depends on SOUND_OSS_CORE
default y
help
With this option enabled, the kernel will claim all OSS device
numbers if any OSS support (native or emulation) is enabled
whether the respective module is loaded or not and try to load the
appropriate module using sound-slot/service-* and char-major-*
module aliases when one of the device numbers is opened. With
this option disabled, kernel will only claim actually in-use
device numbers and opening a missing device will generate only the
standard char-major-* aliases.
The only visible difference is use of additional module aliases
and whether OSS sound devices appear multiple times in
/proc/devices. sound-slot/service-* module aliases are scheduled
to be removed (ie. PRECLAIM won't be available) and this option is
to make the transition easier. This option can be overridden
during boot using the kernel parameter soundcore.preclaim_oss.
Disabling this allows alternative OSS implementations.
Please read Documentation/feature-removal-schedule.txt for
details.
If unusre, say Y.
source "sound/oss/dmasound/Kconfig"
if !M68K

View file

@ -127,6 +127,46 @@ extern int msnd_classic_init(void);
extern int msnd_pinnacle_init(void);
#endif
/*
* By default, OSS sound_core claims full legacy minor range (0-255)
* of SOUND_MAJOR to trap open attempts to any sound minor and
* requests modules using custom sound-slot/service-* module aliases.
* The only benefit of doing this is allowing use of custom module
* aliases instead of the standard char-major-* ones. This behavior
* prevents alternative OSS implementation and is scheduled to be
* removed.
*
* CONFIG_SOUND_OSS_CORE_PRECLAIM and soundcore.preclaim_oss kernel
* parameter are added to allow distros and developers to try and
* switch to alternative implementations without needing to rebuild
* the kernel in the meantime. If preclaim_oss is non-zero, the
* kernel will behave the same as before. All SOUND_MAJOR minors are
* preclaimed and the custom module aliases along with standard chrdev
* ones are emitted if a missing device is opened. If preclaim_oss is
* zero, sound_core only grabs what's actually in use and for missing
* devices only the standard chrdev aliases are requested.
*
* All these clutters are scheduled to be removed along with
* sound-slot/service-* module aliases. Please take a look at
* feature-removal-schedule.txt for details.
*/
#ifdef CONFIG_SOUND_OSS_CORE_PRECLAIM
static int preclaim_oss = 1;
#else
static int preclaim_oss = 0;
#endif
module_param(preclaim_oss, int, 0444);
static int soundcore_open(struct inode *, struct file *);
static const struct file_operations soundcore_fops =
{
/* We must have an owner or the module locking fails */
.owner = THIS_MODULE,
.open = soundcore_open,
};
/*
* Low level list operator. Scan the ordered list, find a hole and
* join into it. Called with the lock asserted
@ -219,8 +259,9 @@ static int sound_insert_unit(struct sound_unit **list, const struct file_operati
if (!s)
return -ENOMEM;
spin_lock(&sound_loader_lock);
retry:
r = __sound_insert_unit(s, list, fops, index, low, top);
spin_unlock(&sound_loader_lock);
@ -231,11 +272,31 @@ static int sound_insert_unit(struct sound_unit **list, const struct file_operati
else
sprintf(s->name, "sound/%s%d", name, r / SOUND_STEP);
if (!preclaim_oss) {
/*
* Something else might have grabbed the minor. If
* first free slot is requested, rescan with @low set
* to the next unit; otherwise, -EBUSY.
*/
r = __register_chrdev(SOUND_MAJOR, s->unit_minor, 1, s->name,
&soundcore_fops);
if (r < 0) {
spin_lock(&sound_loader_lock);
__sound_remove_unit(list, s->unit_minor);
if (index < 0) {
low = s->unit_minor + SOUND_STEP;
goto retry;
}
spin_unlock(&sound_loader_lock);
return -EBUSY;
}
}
device_create(sound_class, dev, MKDEV(SOUND_MAJOR, s->unit_minor),
NULL, s->name+6);
return r;
return s->unit_minor;
fail:
fail:
kfree(s);
return r;
}
@ -254,6 +315,9 @@ static void sound_remove_unit(struct sound_unit **list, int unit)
p = __sound_remove_unit(list, unit);
spin_unlock(&sound_loader_lock);
if (p) {
if (!preclaim_oss)
__unregister_chrdev(SOUND_MAJOR, p->unit_minor, 1,
p->name);
device_destroy(sound_class, MKDEV(SOUND_MAJOR, p->unit_minor));
kfree(p);
}
@ -491,19 +555,6 @@ void unregister_sound_dsp(int unit)
EXPORT_SYMBOL(unregister_sound_dsp);
/*
* Now our file operations
*/
static int soundcore_open(struct inode *, struct file *);
static const struct file_operations soundcore_fops=
{
/* We must have an owner or the module locking fails */
.owner = THIS_MODULE,
.open = soundcore_open,
};
static struct sound_unit *__look_for_unit(int chain, int unit)
{
struct sound_unit *s;
@ -539,8 +590,9 @@ static int soundcore_open(struct inode *inode, struct file *file)
s = __look_for_unit(chain, unit);
if (s)
new_fops = fops_get(s->unit_fops);
if (!new_fops) {
if (preclaim_oss && !new_fops) {
spin_unlock(&sound_loader_lock);
/*
* Please, don't change this order or code.
* For ALSA slot means soundcard and OSS emulation code
@ -550,6 +602,17 @@ static int soundcore_open(struct inode *inode, struct file *file)
*/
request_module("sound-slot-%i", unit>>4);
request_module("sound-service-%i-%i", unit>>4, chain);
/*
* sound-slot/service-* module aliases are scheduled
* for removal in favor of the standard char-major-*
* module aliases. For the time being, generate both
* the legacy and standard module aliases to ease
* transition.
*/
if (request_module("char-major-%d-%d", SOUND_MAJOR, unit) > 0)
request_module("char-major-%d", SOUND_MAJOR);
spin_lock(&sound_loader_lock);
s = __look_for_unit(chain, unit);
if (s)
@ -593,7 +656,8 @@ static void cleanup_oss_soundcore(void)
static int __init init_oss_soundcore(void)
{
if (register_chrdev(SOUND_MAJOR, "sound", &soundcore_fops)==-1) {
if (preclaim_oss &&
register_chrdev(SOUND_MAJOR, "sound", &soundcore_fops) == -1) {
printk(KERN_ERR "soundcore: sound device already in use.\n");
return -EBUSY;
}