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![Takashi Iwai](/assets/img/avatar_default.png)
ALSA sequencer core has a mechanism to load the enumerated devices automatically, and it's performed in an off-load work. This seems causing some race when a sequencer is removed while the pending autoload work is running. As syzkaller spotted, it may lead to some use-after-free: BUG: KASAN: use-after-free in snd_rawmidi_dev_seq_free+0x69/0x70 sound/core/rawmidi.c:1617 Write of size 8 at addr ffff88006c611d90 by task kworker/2:1/567 CPU: 2 PID: 567 Comm: kworker/2:1 Not tainted 4.13.0+ #29 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 Workqueue: events autoload_drivers Call Trace: __dump_stack lib/dump_stack.c:16 [inline] dump_stack+0x192/0x22c lib/dump_stack.c:52 print_address_description+0x78/0x280 mm/kasan/report.c:252 kasan_report_error mm/kasan/report.c:351 [inline] kasan_report+0x230/0x340 mm/kasan/report.c:409 __asan_report_store8_noabort+0x1c/0x20 mm/kasan/report.c:435 snd_rawmidi_dev_seq_free+0x69/0x70 sound/core/rawmidi.c:1617 snd_seq_dev_release+0x4f/0x70 sound/core/seq_device.c:192 device_release+0x13f/0x210 drivers/base/core.c:814 kobject_cleanup lib/kobject.c:648 [inline] kobject_release lib/kobject.c:677 [inline] kref_put include/linux/kref.h:70 [inline] kobject_put+0x145/0x240 lib/kobject.c:694 put_device+0x25/0x30 drivers/base/core.c:1799 klist_devices_put+0x36/0x40 drivers/base/bus.c:827 klist_next+0x264/0x4a0 lib/klist.c:403 next_device drivers/base/bus.c:270 [inline] bus_for_each_dev+0x17e/0x210 drivers/base/bus.c:312 autoload_drivers+0x3b/0x50 sound/core/seq_device.c:117 process_one_work+0x9fb/0x1570 kernel/workqueue.c:2097 worker_thread+0x1e4/0x1350 kernel/workqueue.c:2231 kthread+0x324/0x3f0 kernel/kthread.c:231 ret_from_fork+0x25/0x30 arch/x86/entry/entry_64.S:425 The fix is simply to assure canceling the autoload work at removing the device. Reported-by: Andrey Konovalov <andreyknvl@google.com> Tested-by: Andrey Konovalov <andreyknvl@google.com> Cc: <stable@vger.kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
318 lines
7.8 KiB
C
318 lines
7.8 KiB
C
/*
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* ALSA sequencer device management
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* Copyright (c) 1999 by Takashi Iwai <tiwai@suse.de>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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*
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*----------------------------------------------------------------
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*
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* This device handler separates the card driver module from sequencer
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* stuff (sequencer core, synth drivers, etc), so that user can avoid
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* to spend unnecessary resources e.g. if he needs only listening to
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* MP3s.
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*
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* The card (or lowlevel) driver creates a sequencer device entry
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* via snd_seq_device_new(). This is an entry pointer to communicate
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* with the sequencer device "driver", which is involved with the
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* actual part to communicate with the sequencer core.
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* Each sequencer device entry has an id string and the corresponding
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* driver with the same id is loaded when required. For example,
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* lowlevel codes to access emu8000 chip on sbawe card are included in
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* emu8000-synth module. To activate this module, the hardware
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* resources like i/o port are passed via snd_seq_device argument.
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*
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*/
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#include <linux/device.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <sound/core.h>
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#include <sound/info.h>
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#include <sound/seq_device.h>
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#include <sound/seq_kernel.h>
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#include <sound/initval.h>
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#include <linux/kmod.h>
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#include <linux/slab.h>
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#include <linux/mutex.h>
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MODULE_AUTHOR("Takashi Iwai <tiwai@suse.de>");
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MODULE_DESCRIPTION("ALSA sequencer device management");
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MODULE_LICENSE("GPL");
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/*
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* bus definition
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*/
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static int snd_seq_bus_match(struct device *dev, struct device_driver *drv)
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{
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struct snd_seq_device *sdev = to_seq_dev(dev);
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struct snd_seq_driver *sdrv = to_seq_drv(drv);
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return strcmp(sdrv->id, sdev->id) == 0 &&
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sdrv->argsize == sdev->argsize;
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}
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static struct bus_type snd_seq_bus_type = {
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.name = "snd_seq",
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.match = snd_seq_bus_match,
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};
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/*
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* proc interface -- just for compatibility
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*/
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#ifdef CONFIG_SND_PROC_FS
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static struct snd_info_entry *info_entry;
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static int print_dev_info(struct device *dev, void *data)
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{
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struct snd_seq_device *sdev = to_seq_dev(dev);
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struct snd_info_buffer *buffer = data;
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snd_iprintf(buffer, "snd-%s,%s,%d\n", sdev->id,
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dev->driver ? "loaded" : "empty",
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dev->driver ? 1 : 0);
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return 0;
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}
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static void snd_seq_device_info(struct snd_info_entry *entry,
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struct snd_info_buffer *buffer)
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{
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bus_for_each_dev(&snd_seq_bus_type, NULL, buffer, print_dev_info);
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}
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#endif
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/*
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* load all registered drivers (called from seq_clientmgr.c)
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*/
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#ifdef CONFIG_MODULES
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/* flag to block auto-loading */
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static atomic_t snd_seq_in_init = ATOMIC_INIT(1); /* blocked as default */
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static int request_seq_drv(struct device *dev, void *data)
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{
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struct snd_seq_device *sdev = to_seq_dev(dev);
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if (!dev->driver)
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request_module("snd-%s", sdev->id);
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return 0;
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}
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static void autoload_drivers(struct work_struct *work)
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{
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/* avoid reentrance */
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if (atomic_inc_return(&snd_seq_in_init) == 1)
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bus_for_each_dev(&snd_seq_bus_type, NULL, NULL,
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request_seq_drv);
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atomic_dec(&snd_seq_in_init);
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}
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static DECLARE_WORK(autoload_work, autoload_drivers);
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static void queue_autoload_drivers(void)
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{
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schedule_work(&autoload_work);
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}
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void snd_seq_autoload_init(void)
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{
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atomic_dec(&snd_seq_in_init);
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#ifdef CONFIG_SND_SEQUENCER_MODULE
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/* initial autoload only when snd-seq is a module */
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queue_autoload_drivers();
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#endif
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}
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EXPORT_SYMBOL(snd_seq_autoload_init);
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void snd_seq_autoload_exit(void)
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{
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atomic_inc(&snd_seq_in_init);
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}
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EXPORT_SYMBOL(snd_seq_autoload_exit);
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void snd_seq_device_load_drivers(void)
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{
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queue_autoload_drivers();
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flush_work(&autoload_work);
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}
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EXPORT_SYMBOL(snd_seq_device_load_drivers);
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#define cancel_autoload_drivers() cancel_work_sync(&autoload_work)
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#else
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#define queue_autoload_drivers() /* NOP */
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#define cancel_autoload_drivers() /* NOP */
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#endif
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/*
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* device management
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*/
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static int snd_seq_device_dev_free(struct snd_device *device)
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{
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struct snd_seq_device *dev = device->device_data;
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cancel_autoload_drivers();
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put_device(&dev->dev);
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return 0;
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}
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static int snd_seq_device_dev_register(struct snd_device *device)
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{
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struct snd_seq_device *dev = device->device_data;
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int err;
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err = device_add(&dev->dev);
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if (err < 0)
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return err;
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if (!dev->dev.driver)
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queue_autoload_drivers();
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return 0;
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}
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static int snd_seq_device_dev_disconnect(struct snd_device *device)
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{
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struct snd_seq_device *dev = device->device_data;
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device_del(&dev->dev);
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return 0;
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}
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static void snd_seq_dev_release(struct device *dev)
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{
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struct snd_seq_device *sdev = to_seq_dev(dev);
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if (sdev->private_free)
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sdev->private_free(sdev);
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kfree(sdev);
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}
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/*
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* register a sequencer device
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* card = card info
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* device = device number (if any)
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* id = id of driver
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* result = return pointer (NULL allowed if unnecessary)
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*/
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int snd_seq_device_new(struct snd_card *card, int device, const char *id,
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int argsize, struct snd_seq_device **result)
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{
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struct snd_seq_device *dev;
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int err;
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static struct snd_device_ops dops = {
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.dev_free = snd_seq_device_dev_free,
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.dev_register = snd_seq_device_dev_register,
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.dev_disconnect = snd_seq_device_dev_disconnect,
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};
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if (result)
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*result = NULL;
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if (snd_BUG_ON(!id))
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return -EINVAL;
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dev = kzalloc(sizeof(*dev) + argsize, GFP_KERNEL);
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if (!dev)
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return -ENOMEM;
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/* set up device info */
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dev->card = card;
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dev->device = device;
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dev->id = id;
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dev->argsize = argsize;
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device_initialize(&dev->dev);
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dev->dev.parent = &card->card_dev;
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dev->dev.bus = &snd_seq_bus_type;
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dev->dev.release = snd_seq_dev_release;
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dev_set_name(&dev->dev, "%s-%d-%d", dev->id, card->number, device);
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/* add this device to the list */
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err = snd_device_new(card, SNDRV_DEV_SEQUENCER, dev, &dops);
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if (err < 0) {
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put_device(&dev->dev);
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return err;
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}
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if (result)
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*result = dev;
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return 0;
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}
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EXPORT_SYMBOL(snd_seq_device_new);
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/*
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* driver registration
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*/
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int __snd_seq_driver_register(struct snd_seq_driver *drv, struct module *mod)
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{
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if (WARN_ON(!drv->driver.name || !drv->id))
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return -EINVAL;
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drv->driver.bus = &snd_seq_bus_type;
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drv->driver.owner = mod;
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return driver_register(&drv->driver);
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}
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EXPORT_SYMBOL_GPL(__snd_seq_driver_register);
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void snd_seq_driver_unregister(struct snd_seq_driver *drv)
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{
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driver_unregister(&drv->driver);
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}
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EXPORT_SYMBOL_GPL(snd_seq_driver_unregister);
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/*
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* module part
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*/
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static int __init seq_dev_proc_init(void)
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{
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#ifdef CONFIG_SND_PROC_FS
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info_entry = snd_info_create_module_entry(THIS_MODULE, "drivers",
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snd_seq_root);
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if (info_entry == NULL)
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return -ENOMEM;
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info_entry->content = SNDRV_INFO_CONTENT_TEXT;
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info_entry->c.text.read = snd_seq_device_info;
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if (snd_info_register(info_entry) < 0) {
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snd_info_free_entry(info_entry);
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return -ENOMEM;
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}
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#endif
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return 0;
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}
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static int __init alsa_seq_device_init(void)
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{
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int err;
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err = bus_register(&snd_seq_bus_type);
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if (err < 0)
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return err;
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err = seq_dev_proc_init();
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if (err < 0)
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bus_unregister(&snd_seq_bus_type);
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return err;
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}
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static void __exit alsa_seq_device_exit(void)
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{
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#ifdef CONFIG_MODULES
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cancel_work_sync(&autoload_work);
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#endif
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#ifdef CONFIG_SND_PROC_FS
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snd_info_free_entry(info_entry);
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#endif
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bus_unregister(&snd_seq_bus_type);
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}
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subsys_initcall(alsa_seq_device_init)
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module_exit(alsa_seq_device_exit)
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