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>
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
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
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);
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;
}
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);
}
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;
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);
/*
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;
}
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