diff options
| -rw-r--r-- | Documentation/feature-removal-schedule.txt | 24 | ||||
| -rw-r--r-- | sound/Kconfig | 28 | ||||
| -rw-r--r-- | sound/sound_core.c | 88 |
3 files changed, 122 insertions, 18 deletions
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt index 09e031c..f0690bb 100644 --- a/Documentation/feature-removal-schedule.txt +++ b/Documentation/feature-removal-schedule.txt @@ -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> diff --git a/sound/Kconfig b/sound/Kconfig index 1eceb85..439e15c 100644 --- a/sound/Kconfig +++ b/sound/Kconfig @@ -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 diff --git a/sound/sound_core.c b/sound/sound_core.c index 786067c..bb4b88e 100644 --- a/sound/sound_core.c +++ b/sound/sound_core.c @@ -128,6 +128,46 @@ 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; @@ -539,7 +590,7 @@ 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); /* @@ -605,7 +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; } |