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[media] rc: add locking to fix register/show race
When device_add is called in rc_register_device, the rc sysfs nodes show up, and there's a window in which ir-keytable can be launched via udev and trigger a show_protocols call, which runs without various rc_dev fields filled in yet. Add some locking around registration and store/show_protocols to prevent that from happening. The problem manifests thusly: [64692.957872] BUG: unable to handle kernel NULL pointer dereference at 0000000000000090 [64692.957878] IP: [<ffffffffa036a4c1>] show_protocols+0x47/0xf1 [rc_core] [64692.957890] PGD 19cfc7067 PUD 19cfc6067 PMD 0 [64692.957894] Oops: 0000 [#1] SMP [64692.957897] last sysfs file: /sys/devices/pci0000:00/0000:00:03.1/usb3/3-1/3-1:1.0/rc/rc2/protocols [64692.957902] CPU 3 [64692.957903] Modules linked in: redrat3(+) ir_lirc_codec lirc_dev ir_sony_decoder ir_jvc_decoder ir_rc6_decoder ir_rc5_decoder rc_hauppauge ir_nec _decoder rc_core ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ip6table_filter ip6_tables snd_emu10k1_synth snd_emux_synth snd_seq_virmidi snd_seq_mi di_event snd_seq_midi_emul snd_emu10k1 snd_rawmidi snd_ac97_codec ac97_bus snd_seq snd_pcm snd_seq_device snd_timer snd_page_alloc snd_util_mem pcsp kr tg3 snd_hwdep emu10k1_gp snd amd64_edac_mod gameport edac_core soundcore edac_mce_amd k8temp shpchp i2c_piix4 lm63 e100 mii uinput ipv6 raid0 rai d1 ata_generic firewire_ohci pata_acpi firewire_core crc_itu_t sata_svw pata_serverworks floppy radeon ttm drm_kms_helper drm i2c_algo_bit i2c_core [last unloaded: redrat3] [64692.957949] [64692.957952] Pid: 12265, comm: ir-keytable Tainted: G M W 2.6.39-rc6+ #2 empty empty/TYAN Thunder K8HM S3892 [64692.957957] RIP: 0010:[<ffffffffa036a4c1>] [<ffffffffa036a4c1>] show_protocols+0x47/0xf1 [rc_core] [64692.957962] RSP: 0018:ffff880194509e38 EFLAGS: 00010202 [64692.957964] RAX: 0000000000000000 RBX: ffffffffa036d1e0 RCX: ffffffffa036a47a [64692.957966] RDX: ffff88019a84d000 RSI: ffffffffa036d1e0 RDI: ffff88019cf2f3f0 [64692.957969] RBP: ffff880194509e68 R08: 0000000000000002 R09: 0000000000000000 [64692.957971] R10: 0000000000000002 R11: 0000000000001617 R12: ffff88019a84d000 [64692.957973] R13: 0000000000001000 R14: ffff8801944d2e38 R15: ffff88019ce5f190 [64692.957976] FS: 00007f0a30c9a720(0000) GS:ffff88019fc00000(0000) knlGS:0000000000000000 [64692.957979] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [64692.957981] CR2: 0000000000000090 CR3: 000000019a8e0000 CR4: 00000000000006e0 [64692.957983] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [64692.957986] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [64692.957989] Process ir-keytable (pid: 12265, threadinfo ffff880194508000, task ffff88019a9fc720) [64692.957991] Stack: [64692.957992] 0000000000000002 ffffffffa036d1e0 ffff880194509f58 0000000000001000 [64692.957997] ffff8801944d2e38 ffff88019ce5f190 ffff880194509e98 ffffffff8131484b [64692.958001] ffffffff8118e923 ffffffff810e9b2f ffff880194509e98 ffff8801944d2e18 [64692.958005] Call Trace: [64692.958014] [<ffffffff8131484b>] dev_attr_show+0x27/0x4e [64692.958014] [<ffffffff8118e923>] ? sysfs_read_file+0x94/0x172 [64692.958014] [<ffffffff810e9b2f>] ? __get_free_pages+0x16/0x52 [64692.958014] [<ffffffff8118e94c>] sysfs_read_file+0xbd/0x172 [64692.958014] [<ffffffff8113205e>] vfs_read+0xac/0xf3 [64692.958014] [<ffffffff8113347b>] ? fget_light+0x3a/0xa1 [64692.958014] [<ffffffff811320f2>] sys_read+0x4d/0x74 [64692.958014] [<ffffffff814c19c2>] system_call_fastpath+0x16/0x1b Its a bit difficult to reproduce, but I'm fairly confident this has fixed the problem. Signed-off-by: Jarod Wilson <jarod@redhat.com> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Jarod Wilson
Mauro Carvalho Chehab
parent
51ea62927e
commit
08aeb7c9a4
@ -749,6 +749,9 @@ static struct {
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* it is trigged by reading /sys/class/rc/rc?/protocols.
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* It returns the protocol names of supported protocols.
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* Enabled protocols are printed in brackets.
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*
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* dev->lock is taken to guard against races between device
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* registration, store_protocols and show_protocols.
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*/
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static ssize_t show_protocols(struct device *device,
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struct device_attribute *mattr, char *buf)
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@ -762,6 +765,8 @@ static ssize_t show_protocols(struct device *device,
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if (!dev)
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return -EINVAL;
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mutex_lock(&dev->lock);
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if (dev->driver_type == RC_DRIVER_SCANCODE) {
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enabled = dev->rc_map.rc_type;
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allowed = dev->allowed_protos;
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@ -784,6 +789,9 @@ static ssize_t show_protocols(struct device *device,
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if (tmp != buf)
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tmp--;
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*tmp = '\n';
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mutex_unlock(&dev->lock);
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return tmp + 1 - buf;
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}
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@ -802,6 +810,9 @@ static ssize_t show_protocols(struct device *device,
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* Writing "none" will disable all protocols.
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* Returns -EINVAL if an invalid protocol combination or unknown protocol name
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* is used, otherwise @len.
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*
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* dev->lock is taken to guard against races between device
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* registration, store_protocols and show_protocols.
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*/
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static ssize_t store_protocols(struct device *device,
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struct device_attribute *mattr,
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@ -815,18 +826,22 @@ static ssize_t store_protocols(struct device *device,
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u64 mask;
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int rc, i, count = 0;
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unsigned long flags;
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ssize_t ret;
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/* Device is being removed */
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if (!dev)
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return -EINVAL;
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mutex_lock(&dev->lock);
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if (dev->driver_type == RC_DRIVER_SCANCODE)
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type = dev->rc_map.rc_type;
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else if (dev->raw)
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type = dev->raw->enabled_protocols;
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else {
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IR_dprintk(1, "Protocol switching not supported\n");
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return -EINVAL;
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ret = -EINVAL;
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goto out;
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}
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while ((tmp = strsep((char **) &data, " \n")) != NULL) {
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@ -860,7 +875,8 @@ static ssize_t store_protocols(struct device *device,
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}
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if (i == ARRAY_SIZE(proto_names)) {
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IR_dprintk(1, "Unknown protocol: '%s'\n", tmp);
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return -EINVAL;
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ret = -EINVAL;
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goto out;
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}
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count++;
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}
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@ -875,7 +891,8 @@ static ssize_t store_protocols(struct device *device,
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if (!count) {
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IR_dprintk(1, "Protocol not specified\n");
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return -EINVAL;
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ret = -EINVAL;
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goto out;
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}
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if (dev->change_protocol) {
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@ -883,7 +900,8 @@ static ssize_t store_protocols(struct device *device,
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if (rc < 0) {
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IR_dprintk(1, "Error setting protocols to 0x%llx\n",
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(long long)type);
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return -EINVAL;
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ret = -EINVAL;
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goto out;
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}
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}
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@ -898,7 +916,11 @@ static ssize_t store_protocols(struct device *device,
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IR_dprintk(1, "Current protocol(s): 0x%llx\n",
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(long long)type);
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return len;
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ret = len;
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out:
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mutex_unlock(&dev->lock);
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return ret;
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}
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static void rc_dev_release(struct device *device)
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@ -974,6 +996,7 @@ struct rc_dev *rc_allocate_device(void)
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spin_lock_init(&dev->rc_map.lock);
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spin_lock_init(&dev->keylock);
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mutex_init(&dev->lock);
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setup_timer(&dev->timer_keyup, ir_timer_keyup, (unsigned long)dev);
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dev->dev.type = &rc_dev_type;
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@ -1019,12 +1042,21 @@ int rc_register_device(struct rc_dev *dev)
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if (dev->close)
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dev->input_dev->close = ir_close;
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/*
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* Take the lock here, as the device sysfs node will appear
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* when device_add() is called, which may trigger an ir-keytable udev
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* rule, which will in turn call show_protocols and access either
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* dev->rc_map.rc_type or dev->raw->enabled_protocols before it has
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* been initialized.
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*/
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mutex_lock(&dev->lock);
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dev->devno = (unsigned long)(atomic_inc_return(&devno) - 1);
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dev_set_name(&dev->dev, "rc%ld", dev->devno);
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dev_set_drvdata(&dev->dev, dev);
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rc = device_add(&dev->dev);
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if (rc)
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return rc;
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goto out_unlock;
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rc = ir_setkeytable(dev, rc_map);
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if (rc)
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@ -1058,6 +1090,7 @@ int rc_register_device(struct rc_dev *dev)
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if (rc < 0)
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goto out_input;
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}
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mutex_unlock(&dev->lock);
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if (dev->change_protocol) {
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rc = dev->change_protocol(dev, rc_map->rc_type);
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@ -1083,6 +1116,8 @@ out_table:
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ir_free_table(&dev->rc_map);
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out_dev:
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device_del(&dev->dev);
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out_unlock:
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mutex_unlock(&dev->lock);
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return rc;
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}
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EXPORT_SYMBOL_GPL(rc_register_device);
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@ -40,10 +40,12 @@ enum rc_driver_type {
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* @driver_name: name of the hardware driver which registered this device
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* @map_name: name of the default keymap
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* @rc_map: current scan/key table
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* @lock: used to ensure we've filled in all protocol details before
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* anyone can call show_protocols or store_protocols
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* @devno: unique remote control device number
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* @raw: additional data for raw pulse/space devices
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* @input_dev: the input child device used to communicate events to userspace
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* @driver_type: specifies if protocol decoding is done in hardware or software
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* @driver_type: specifies if protocol decoding is done in hardware or software
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* @idle: used to keep track of RX state
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* @allowed_protos: bitmask with the supported RC_TYPE_* protocols
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* @scanmask: some hardware decoders are not capable of providing the full
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@ -86,7 +88,8 @@ struct rc_dev {
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struct input_id input_id;
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char *driver_name;
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const char *map_name;
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struct rc_map rc_map;
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struct rc_map rc_map;
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struct mutex lock;
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unsigned long devno;
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struct ir_raw_event_ctrl *raw;
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struct input_dev *input_dev;
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