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![Arjan van de Ven](/assets/img/avatar_default.png)
Many struct file_operations in the kernel can be "const". Marking them const moves these to the .rodata section, which avoids false sharing with potential dirty data. In addition it'll catch accidental writes at compile time to these shared resources. Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
547 lines
13 KiB
C
547 lines
13 KiB
C
/*
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* Sound core handling. Breaks out sound functions to submodules
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*
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* Author: Alan Cox <alan.cox@linux.org>
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*
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* Fixes:
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*
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* --------------------
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*
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* Top level handler for the sound subsystem. Various devices can
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* plug into this. The fact they don't all go via OSS doesn't mean
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* they don't have to implement the OSS API. There is a lot of logic
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* to keeping much of the OSS weight out of the code in a compatibility
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* module, but it's up to the driver to rember to load it...
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*
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* The code provides a set of functions for registration of devices
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* by type. This is done rather than providing a single call so that
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* we can hide any future changes in the internals (eg when we go to
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* 32bit dev_t) from the modules and their interface.
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*
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* Secondly we need to allocate the dsp, dsp16 and audio devices as
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* one. Thus we misuse the chains a bit to simplify this.
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*
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* Thirdly to make it more fun and for 2.3.x and above we do all
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* of this using fine grained locking.
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*
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* FIXME: we have to resolve modules and fine grained load/unload
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* locking at some point in 2.3.x.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/fs.h>
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#include <linux/sound.h>
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#include <linux/major.h>
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#include <linux/kmod.h>
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#include <linux/device.h>
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#define SOUND_STEP 16
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struct sound_unit
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{
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int unit_minor;
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const struct file_operations *unit_fops;
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struct sound_unit *next;
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char name[32];
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};
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#ifdef CONFIG_SOUND_MSNDCLAS
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extern int msnd_classic_init(void);
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#endif
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#ifdef CONFIG_SOUND_MSNDPIN
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extern int msnd_pinnacle_init(void);
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#endif
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struct class *sound_class;
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EXPORT_SYMBOL(sound_class);
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/*
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* Low level list operator. Scan the ordered list, find a hole and
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* join into it. Called with the lock asserted
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*/
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static int __sound_insert_unit(struct sound_unit * s, struct sound_unit **list, const struct file_operations *fops, int index, int low, int top)
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{
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int n=low;
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if (index < 0) { /* first free */
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while (*list && (*list)->unit_minor<n)
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list=&((*list)->next);
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while(n<top)
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{
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/* Found a hole ? */
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if(*list==NULL || (*list)->unit_minor>n)
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break;
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list=&((*list)->next);
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n+=SOUND_STEP;
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}
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if(n>=top)
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return -ENOENT;
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} else {
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n = low+(index*16);
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while (*list) {
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if ((*list)->unit_minor==n)
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return -EBUSY;
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if ((*list)->unit_minor>n)
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break;
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list=&((*list)->next);
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}
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}
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/*
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* Fill it in
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*/
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s->unit_minor=n;
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s->unit_fops=fops;
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/*
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* Link it
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*/
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s->next=*list;
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*list=s;
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return n;
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}
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/*
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* Remove a node from the chain. Called with the lock asserted
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*/
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static struct sound_unit *__sound_remove_unit(struct sound_unit **list, int unit)
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{
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while(*list)
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{
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struct sound_unit *p=*list;
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if(p->unit_minor==unit)
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{
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*list=p->next;
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return p;
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}
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list=&(p->next);
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}
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printk(KERN_ERR "Sound device %d went missing!\n", unit);
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return NULL;
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}
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/*
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* This lock guards the sound loader list.
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*/
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static DEFINE_SPINLOCK(sound_loader_lock);
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/*
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* Allocate the controlling structure and add it to the sound driver
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* list. Acquires locks as needed
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*/
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static int sound_insert_unit(struct sound_unit **list, const struct file_operations *fops, int index, int low, int top, const char *name, umode_t mode, struct device *dev)
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{
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struct sound_unit *s = kmalloc(sizeof(*s), GFP_KERNEL);
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int r;
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if (!s)
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return -ENOMEM;
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spin_lock(&sound_loader_lock);
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r = __sound_insert_unit(s, list, fops, index, low, top);
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spin_unlock(&sound_loader_lock);
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if (r < 0)
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goto fail;
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else if (r < SOUND_STEP)
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sprintf(s->name, "sound/%s", name);
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else
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sprintf(s->name, "sound/%s%d", name, r / SOUND_STEP);
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device_create(sound_class, dev, MKDEV(SOUND_MAJOR, s->unit_minor),
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s->name+6);
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return r;
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fail:
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kfree(s);
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return r;
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}
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/*
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* Remove a unit. Acquires locks as needed. The drivers MUST have
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* completed the removal before their file operations become
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* invalid.
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*/
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static void sound_remove_unit(struct sound_unit **list, int unit)
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{
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struct sound_unit *p;
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spin_lock(&sound_loader_lock);
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p = __sound_remove_unit(list, unit);
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spin_unlock(&sound_loader_lock);
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if (p) {
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device_destroy(sound_class, MKDEV(SOUND_MAJOR, p->unit_minor));
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kfree(p);
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}
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}
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/*
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* Allocations
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*
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* 0 *16 Mixers
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* 1 *8 Sequencers
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* 2 *16 Midi
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* 3 *16 DSP
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* 4 *16 SunDSP
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* 5 *16 DSP16
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* 6 -- sndstat (obsolete)
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* 7 *16 unused
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* 8 -- alternate sequencer (see above)
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* 9 *16 raw synthesizer access
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* 10 *16 unused
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* 11 *16 unused
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* 12 *16 unused
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* 13 *16 unused
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* 14 *16 unused
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* 15 *16 unused
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*/
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static struct sound_unit *chains[SOUND_STEP];
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/**
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* register_sound_special_device - register a special sound node
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* @fops: File operations for the driver
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* @unit: Unit number to allocate
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* @dev: device pointer
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*
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* Allocate a special sound device by minor number from the sound
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* subsystem. The allocated number is returned on succes. On failure
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* a negative error code is returned.
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*/
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int register_sound_special_device(const struct file_operations *fops, int unit,
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struct device *dev)
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{
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const int chain = unit % SOUND_STEP;
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int max_unit = 128 + chain;
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const char *name;
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char _name[16];
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switch (chain) {
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case 0:
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name = "mixer";
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break;
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case 1:
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name = "sequencer";
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if (unit >= SOUND_STEP)
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goto __unknown;
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max_unit = unit + 1;
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break;
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case 2:
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name = "midi";
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break;
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case 3:
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name = "dsp";
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break;
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case 4:
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name = "audio";
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break;
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case 8:
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name = "sequencer2";
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if (unit >= SOUND_STEP)
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goto __unknown;
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max_unit = unit + 1;
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break;
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case 9:
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name = "dmmidi";
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break;
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case 10:
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name = "dmfm";
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break;
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case 12:
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name = "adsp";
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break;
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case 13:
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name = "amidi";
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break;
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case 14:
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name = "admmidi";
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break;
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default:
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{
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__unknown:
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sprintf(_name, "unknown%d", chain);
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if (unit >= SOUND_STEP)
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strcat(_name, "-");
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name = _name;
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}
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break;
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}
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return sound_insert_unit(&chains[chain], fops, -1, unit, max_unit,
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name, S_IRUSR | S_IWUSR, dev);
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}
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EXPORT_SYMBOL(register_sound_special_device);
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int register_sound_special(const struct file_operations *fops, int unit)
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{
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return register_sound_special_device(fops, unit, NULL);
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}
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EXPORT_SYMBOL(register_sound_special);
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/**
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* register_sound_mixer - register a mixer device
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* @fops: File operations for the driver
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* @dev: Unit number to allocate
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*
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* Allocate a mixer device. Unit is the number of the mixer requested.
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* Pass -1 to request the next free mixer unit. On success the allocated
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* number is returned, on failure a negative error code is returned.
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*/
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int register_sound_mixer(const struct file_operations *fops, int dev)
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{
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return sound_insert_unit(&chains[0], fops, dev, 0, 128,
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"mixer", S_IRUSR | S_IWUSR, NULL);
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}
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EXPORT_SYMBOL(register_sound_mixer);
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/**
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* register_sound_midi - register a midi device
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* @fops: File operations for the driver
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* @dev: Unit number to allocate
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*
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* Allocate a midi device. Unit is the number of the midi device requested.
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* Pass -1 to request the next free midi unit. On success the allocated
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* number is returned, on failure a negative error code is returned.
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*/
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int register_sound_midi(const struct file_operations *fops, int dev)
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{
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return sound_insert_unit(&chains[2], fops, dev, 2, 130,
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"midi", S_IRUSR | S_IWUSR, NULL);
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}
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EXPORT_SYMBOL(register_sound_midi);
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/*
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* DSP's are registered as a triple. Register only one and cheat
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* in open - see below.
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*/
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/**
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* register_sound_dsp - register a DSP device
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* @fops: File operations for the driver
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* @dev: Unit number to allocate
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*
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* Allocate a DSP device. Unit is the number of the DSP requested.
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* Pass -1 to request the next free DSP unit. On success the allocated
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* number is returned, on failure a negative error code is returned.
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*
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* This function allocates both the audio and dsp device entries together
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* and will always allocate them as a matching pair - eg dsp3/audio3
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*/
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int register_sound_dsp(const struct file_operations *fops, int dev)
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{
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return sound_insert_unit(&chains[3], fops, dev, 3, 131,
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"dsp", S_IWUSR | S_IRUSR, NULL);
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}
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EXPORT_SYMBOL(register_sound_dsp);
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/**
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* unregister_sound_special - unregister a special sound device
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* @unit: unit number to allocate
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*
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* Release a sound device that was allocated with
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* register_sound_special(). The unit passed is the return value from
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* the register function.
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*/
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void unregister_sound_special(int unit)
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{
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sound_remove_unit(&chains[unit % SOUND_STEP], unit);
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}
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EXPORT_SYMBOL(unregister_sound_special);
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/**
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* unregister_sound_mixer - unregister a mixer
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* @unit: unit number to allocate
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*
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* Release a sound device that was allocated with register_sound_mixer().
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* The unit passed is the return value from the register function.
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*/
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void unregister_sound_mixer(int unit)
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{
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sound_remove_unit(&chains[0], unit);
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}
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EXPORT_SYMBOL(unregister_sound_mixer);
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/**
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* unregister_sound_midi - unregister a midi device
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* @unit: unit number to allocate
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*
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* Release a sound device that was allocated with register_sound_midi().
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* The unit passed is the return value from the register function.
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*/
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void unregister_sound_midi(int unit)
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{
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return sound_remove_unit(&chains[2], unit);
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}
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EXPORT_SYMBOL(unregister_sound_midi);
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/**
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* unregister_sound_dsp - unregister a DSP device
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* @unit: unit number to allocate
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*
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* Release a sound device that was allocated with register_sound_dsp().
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* The unit passed is the return value from the register function.
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*
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* Both of the allocated units are released together automatically.
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*/
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void unregister_sound_dsp(int unit)
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{
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return sound_remove_unit(&chains[3], unit);
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}
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EXPORT_SYMBOL(unregister_sound_dsp);
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/*
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* Now our file operations
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*/
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static int soundcore_open(struct inode *, struct file *);
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static const struct file_operations soundcore_fops=
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{
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/* We must have an owner or the module locking fails */
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.owner = THIS_MODULE,
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.open = soundcore_open,
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};
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static struct sound_unit *__look_for_unit(int chain, int unit)
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{
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struct sound_unit *s;
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s=chains[chain];
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while(s && s->unit_minor <= unit)
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{
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if(s->unit_minor==unit)
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return s;
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s=s->next;
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}
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return NULL;
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}
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int soundcore_open(struct inode *inode, struct file *file)
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{
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int chain;
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int unit = iminor(inode);
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struct sound_unit *s;
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const struct file_operations *new_fops = NULL;
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chain=unit&0x0F;
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if(chain==4 || chain==5) /* dsp/audio/dsp16 */
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{
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unit&=0xF0;
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unit|=3;
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chain=3;
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}
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spin_lock(&sound_loader_lock);
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s = __look_for_unit(chain, unit);
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if (s)
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new_fops = fops_get(s->unit_fops);
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if (!new_fops) {
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spin_unlock(&sound_loader_lock);
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/*
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* Please, don't change this order or code.
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* For ALSA slot means soundcard and OSS emulation code
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* comes as add-on modules which aren't depend on
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* ALSA toplevel modules for soundcards, thus we need
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* load them at first. [Jaroslav Kysela <perex@jcu.cz>]
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*/
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request_module("sound-slot-%i", unit>>4);
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request_module("sound-service-%i-%i", unit>>4, chain);
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spin_lock(&sound_loader_lock);
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s = __look_for_unit(chain, unit);
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if (s)
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new_fops = fops_get(s->unit_fops);
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}
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if (new_fops) {
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/*
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* We rely upon the fact that we can't be unloaded while the
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* subdriver is there, so if ->open() is successful we can
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* safely drop the reference counter and if it is not we can
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* revert to old ->f_op. Ugly, indeed, but that's the cost of
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* switching ->f_op in the first place.
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*/
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int err = 0;
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const struct file_operations *old_fops = file->f_op;
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file->f_op = new_fops;
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spin_unlock(&sound_loader_lock);
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if(file->f_op->open)
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err = file->f_op->open(inode,file);
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if (err) {
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fops_put(file->f_op);
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file->f_op = fops_get(old_fops);
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}
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fops_put(old_fops);
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return err;
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}
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spin_unlock(&sound_loader_lock);
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return -ENODEV;
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}
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MODULE_DESCRIPTION("Core sound module");
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MODULE_AUTHOR("Alan Cox");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS_CHARDEV_MAJOR(SOUND_MAJOR);
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static void __exit cleanup_soundcore(void)
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{
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/* We have nothing to really do here - we know the lists must be
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empty */
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unregister_chrdev(SOUND_MAJOR, "sound");
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class_destroy(sound_class);
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}
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static int __init init_soundcore(void)
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{
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if (register_chrdev(SOUND_MAJOR, "sound", &soundcore_fops)==-1) {
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printk(KERN_ERR "soundcore: sound device already in use.\n");
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return -EBUSY;
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}
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sound_class = class_create(THIS_MODULE, "sound");
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if (IS_ERR(sound_class))
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return PTR_ERR(sound_class);
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return 0;
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}
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module_init(init_soundcore);
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module_exit(cleanup_soundcore);
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