From 1905b1bfc0de6f69a61dc03cac0d86a04b3216bd Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 6 Aug 2009 18:13:23 +0900 Subject: [PATCH 1/3] chrdev: implement __[un]register_chrdev() [un]register_chrdev() assume minor range 0-255. This patch adds __ prefixed versions which take @minorbase and @count explicitly. Signed-off-by: Tejun Heo Cc: Al Viro Cc: Greg Kroah-Hartman Signed-off-by: Takashi Iwai --- fs/char_dev.c | 39 ++++++++++++++++++++++++++------------- include/linux/fs.h | 19 ++++++++++++++++--- 2 files changed, 42 insertions(+), 16 deletions(-) diff --git a/fs/char_dev.c b/fs/char_dev.c index a173551e19d7..2f18c1e4e301 100644 --- a/fs/char_dev.c +++ b/fs/char_dev.c @@ -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); diff --git a/include/linux/fs.h b/include/linux/fs.h index a36ffa5a77a4..6c36ab788854 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -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 */ From 0a848680a82e47854347cdfecbe9adf8842719e6 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 6 Aug 2009 18:13:58 +0900 Subject: [PATCH 2/3] sound: request char-major-* module aliases for missing OSS devices Till now missing OSS devices emitted sound-slot/service-* module alises instead of the standard char-major-* if a missing device number is opened if soundcore is loaded. The custom module aliases don't have any inherent benefit than backward compatibility. sound-slot/service-* module aliases is scheduled to be removed and to help the transition this patch makes soundcore emit the standard module alises along with the custom ones. Signed-off-by: Tejun Heo Cc: Alan Cox Signed-off-by: Takashi Iwai --- sound/sound_core.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/sound/sound_core.c b/sound/sound_core.c index a41f8b127f49..786067c49b01 100644 --- a/sound/sound_core.c +++ b/sound/sound_core.c @@ -541,6 +541,7 @@ static int soundcore_open(struct inode *inode, struct file *file) new_fops = fops_get(s->unit_fops); if (!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 +551,17 @@ 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) From 93fe4483e6fd3e71d17cd919de14b3b1f9eb3795 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 6 Aug 2009 18:14:26 +0900 Subject: [PATCH 3/3] sound: make OSS device number claiming optional and schedule its removal If any OSS support is enabled, regardless of built-in or module, sound_core claims full OSS major number (that is, the old 0-255 region) to trap open attempts and request sound modules using custom module aliases. This feature is redundant as chrdev already has such mechanism. This preemptive claiming prevents alternative OSS implementation. The custom module aliases are scheduled to be removed and the previous patch made soundcore emit the standard chrdev aliases too to help transition. This patch schedule the feature for removal in a year and makes it optional so that developers and distros can try new things in the meantime without rebuilding the kernel. The pre-claiming can be turned off by using SOUND_OSS_CORE_PRECLAIM and/or kernel parameter soundcore.preclaim_oss. As this allows sound minors to be individually grabbed by other users, this patch updates sound_insert_unit() such that if registering individual device region fails, it tries the next available slot. For details on removal plan, please read the entry added by this patch in feature-removal-schedule.txt . Signed-off-by: Tejun Heo Cc: Alan Cox Signed-off-by: Takashi Iwai --- Documentation/feature-removal-schedule.txt | 24 ++++++ sound/Kconfig | 28 +++++++ 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 09e031c55887..f0690bbbd73c 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 + +---------------------------- + +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 diff --git a/sound/Kconfig b/sound/Kconfig index 1eceb85287c5..439e15c8faa3 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 786067c49b01..bb4b88e606bb 100644 --- a/sound/sound_core.c +++ b/sound/sound_core.c @@ -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; @@ -539,7 +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; }