中断API之setup_irq【转】

转自：https://blog.csdn.net/tiantao2012/article/details/78957472

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/tiantao2012/article/details/78957472
 
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int setup_irq(unsigned int irq, struct irqaction *act)用于设置irq对应的irqaction.  
 
其使用的例程如下：
struct irq_domain * __init __init_i8259_irqs(struct device_node *node)
{
    struct irq_domain *domain;  
 
    insert_resource(&ioport_resource, &pic1_io_resource);
    insert_resource(&ioport_resource, &pic2_io_resource);  
 
    init_8259A();  
 
    domain = irq_domain_add_legacy(node, , I8259A_IRQ_BASE, ,
                       &i8259A_ops, NULL);
    if (!domain)
        panic("Failed to add i8259 IRQ domain");  
 
    setup_irq(I8259A_IRQ_BASE + PIC_CASCADE_IR, &irq2);
    return domain;
}
其源码分析如下：  
 
int setup_irq(unsigned int irq, struct irqaction *act)
{
    int retval;
    struct irq_desc *desc = irq_to_desc(irq);
    #中断描述为null，或者设置了_IRQ_PER_CPU_DEVID 标志的话，则直接退出
    if (!desc || WARN_ON(irq_settings_is_per_cpu_devid(desc)))
        return -EINVAL;  
 
    retval = irq_chip_pm_get(&desc->irq_data);
    if (retval < )
        return retval;
    #核心代码，设置irq对应的irqaction *act
    retval = __setup_irq(irq, desc, act);  
 
    if (retval)
        irq_chip_pm_put(&desc->irq_data);  
 
    return retval;
}
static int
__setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
{
    struct irqaction *old, **old_ptr;
    unsigned long flags, thread_mask = ;
    int ret, nested, shared = ;
    #中断描述符为null，则退出
    if (!desc)
        return -EINVAL;
    #没有设置irq_data.chip，所以irq_data.chip 会等于no_irq_chip。这属于异常case ，退出.
    if (desc->irq_data.chip == &no_irq_chip)
        return -ENOSYS;
    #增加这个模块的引用计数
    if (!try_module_get(desc->owner))
        return -ENODEV;
    #更新struct irqaction *new 中的irq number
    new->irq = irq;  
 
    /*
     * If the trigger type is not specified by the caller,
     * then use the default for this interrupt.
     */
     #没有设置中断触发类型的话，则用默认值.
    if (!(new->flags & IRQF_TRIGGER_MASK))
        new->flags |= irqd_get_trigger_type(&desc->irq_data);  
 
    /*
     * Check whether the interrupt nests into another interrupt
     * thread.
     */
    #检查这里是否是中断嵌套，正常情况下irq_chip 基本都不支持中断嵌套
    nested = irq_settings_is_nested_thread(desc);
    if (nested) {
        if (!new->thread_fn) {
            ret = -EINVAL;
            goto out_mput;
        }
        /*
         * Replace the primary handler which was provided from
         * the driver for non nested interrupt handling by the
         * dummy function which warns when called.
         */
        new->handler = irq_nested_primary_handler;
    } else {
    #这里检查是否为这个中断设置一个thread，也就是说是否支持中断线程化
        if (irq_settings_can_thread(desc)) {
            ret = irq_setup_forced_threading(new);
            if (ret)
                goto out_mput;
        }
    }  
 
    /*
     * Create a handler thread when a thread function is supplied
     * and the interrupt does not nest into another interrupt
     * thread.
     */
    #在没有支持中断嵌套且用户用设置中断线程的情况下,这里会创建一个中断线程
    if (new->thread_fn && !nested) {
        ret = setup_irq_thread(new, irq, false);
        if (ret)
            goto out_mput;
        #中断线程化时是否支持第二个线程。如果支持的话，再创建一个中断线程.
        if (new->secondary) {
            ret = setup_irq_thread(new->secondary, irq, true);
            if (ret)
                goto out_thread;
        }
    }  
 
    /*
     * Drivers are often written to work w/o knowledge about the
     * underlying irq chip implementation, so a request for a
     * threaded irq without a primary hard irq context handler
     * requires the ONESHOT flag to be set. Some irq chips like
     * MSI based interrupts are per se one shot safe. Check the
     * chip flags, so we can avoid the unmask dance at the end of
     * the threaded handler for those.
     */
    #有设置oneshot 标志的话，则清掉这个标志.
    if (desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)
        new->flags &= ~IRQF_ONESHOT;  
 
    /*
     * Protects against a concurrent __free_irq() call which might wait
     * for synchronize_irq() to complete without holding the optional
     * chip bus lock and desc->lock.
     */
    mutex_lock(&desc->request_mutex);  
 
    /*
     * Acquire bus lock as the irq_request_resources() callback below
     * might rely on the serialization or the magic power management
     * functions which are abusing the irq_bus_lock() callback,
     */
    chip_bus_lock(desc);  
 
    /* First installed action requests resources. */
    #中断描述符的action为null的话，则通过irq_request_resources 来申请中断资源.
    if (!desc->action) {
        ret = irq_request_resources(desc);
        if (ret) {
            pr_err("Failed to request resources for %s (irq %d) on irqchip %s\n",
                   new->name, irq, desc->irq_data.chip->name);
            goto out_bus_unlock;
        }
    }  
 
    /*
     * The following block of code has to be executed atomically
     * protected against a concurrent interrupt and any of the other
     * management calls which are not serialized via
     * desc->request_mutex or the optional bus lock.
     */
    raw_spin_lock_irqsave(&desc->lock, flags);
    old_ptr = &desc->action;
    old = *old_ptr;
    #如果这个中断号对应的中断描述符中的action 不为null，说明这个中断号之前可能已经申请过中断了
    #这里同样可以得出结论，同一个中断好，可以重复申请中断，但是可能会继承前一次的中断触发类型.
    if (old) {
        /*
         * Can't share interrupts unless both agree to and are
         * the same type (level, edge, polarity). So both flag
         * fields must have IRQF_SHARED set and the bits which
         * set the trigger type must match. Also all must
         * agree on ONESHOT.
         */
        unsigned int oldtype;  
 
        /*
         * If nobody did set the configuration before, inherit
         * the one provided by the requester.
         */
        if (irqd_trigger_type_was_set(&desc->irq_data)) {
            oldtype = irqd_get_trigger_type(&desc->irq_data);
        } else {
            oldtype = new->flags & IRQF_TRIGGER_MASK;
            irqd_set_trigger_type(&desc->irq_data, oldtype);
        }  
 
        if (!((old->flags & new->flags) & IRQF_SHARED) ||
            (oldtype != (new->flags & IRQF_TRIGGER_MASK)) ||
            ((old->flags ^ new->flags) & IRQF_ONESHOT))
            goto mismatch;  
 
        /* All handlers must agree on per-cpuness */
        if ((old->flags & IRQF_PERCPU) !=
            (new->flags & IRQF_PERCPU))
            goto mismatch;  
 
        /* add new interrupt at end of irq queue */
        do {
            /*
             * Or all existing action->thread_mask bits,
             * so we can find the next zero bit for this
             * new action.
             */
            thread_mask |= old->thread_mask;
            old_ptr = &old->next;
            old = *old_ptr;
        } while (old);
        shared = ;
    }  
 
    /*
     * Setup the thread mask for this irqaction for ONESHOT. For
     * !ONESHOT irqs the thread mask is 0 so we can avoid a
     * conditional in irq_wake_thread().
     */
    if (new->flags & IRQF_ONESHOT) {
        /*
         * Unlikely to have 32 resp 64 irqs sharing one line,
         * but who knows.
         */
        if (thread_mask == ~0UL) {
            ret = -EBUSY;
            goto out_unlock;
        }
        /*
         * The thread_mask for the action is or'ed to
         * desc->thread_active to indicate that the
         * IRQF_ONESHOT thread handler has been woken, but not
         * yet finished. The bit is cleared when a thread
         * completes. When all threads of a shared interrupt
         * line have completed desc->threads_active becomes
         * zero and the interrupt line is unmasked. See
         * handle.c:irq_wake_thread() for further information.
         *
         * If no thread is woken by primary (hard irq context)
         * interrupt handlers, then desc->threads_active is
         * also checked for zero to unmask the irq line in the
         * affected hard irq flow handlers
         * (handle_[fasteoi|level]_irq).
         *
         * The new action gets the first zero bit of
         * thread_mask assigned. See the loop above which or's
         * all existing action->thread_mask bits.
         */
        new->thread_mask = 1UL << ffz(thread_mask);  
 
    } else if (new->handler == irq_default_primary_handler &&
           !(desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)) {
        /*
         * The interrupt was requested with handler = NULL, so
         * we use the default primary handler for it. But it
         * does not have the oneshot flag set. In combination
         * with level interrupts this is deadly, because the
         * default primary handler just wakes the thread, then
         * the irq lines is reenabled, but the device still
         * has the level irq asserted. Rinse and repeat....
         *
         * While this works for edge type interrupts, we play
         * it safe and reject unconditionally because we can't
         * say for sure which type this interrupt really
         * has. The type flags are unreliable as the
         * underlying chip implementation can override them.
         */
        pr_err("Threaded irq requested with handler=NULL and !ONESHOT for irq %d\n",
               irq);
        ret = -EINVAL;
        goto out_unlock;
    }
    #非共享中断
    if (!shared) {
        #初始化一个等待队列，这个等待队列包含在中断描述符中
        init_waitqueue_head(&desc->wait_for_threads);  
 
        /* Setup the type (level, edge polarity) if configured: */
        if (new->flags & IRQF_TRIGGER_MASK) {
            ret = __irq_set_trigger(desc,
                        new->flags & IRQF_TRIGGER_MASK);  
 
            if (ret)
                goto out_unlock;
        }  
 
        /*
         * Activate the interrupt. That activation must happen
         * independently of IRQ_NOAUTOEN. request_irq() can fail
         * and the callers are supposed to handle
         * that. enable_irq() of an interrupt requested with
         * IRQ_NOAUTOEN is not supposed to fail. The activation
         * keeps it in shutdown mode, it merily associates
         * resources if necessary and if that's not possible it
         * fails. Interrupts which are in managed shutdown mode
         * will simply ignore that activation request.
         */
         #激活这个中断
        ret = irq_activate(desc);
        if (ret)
            goto out_unlock;  
 
        desc->istate &= ~(IRQS_AUTODETECT | IRQS_SPURIOUS_DISABLED | \
                  IRQS_ONESHOT | IRQS_WAITING);
        irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);
        #是不是percpu中断
        if (new->flags & IRQF_PERCPU) {
            irqd_set(&desc->irq_data, IRQD_PER_CPU);
            irq_settings_set_per_cpu(desc);
        }  
 
        if (new->flags & IRQF_ONESHOT)
            desc->istate |= IRQS_ONESHOT;  
 
        /* Exclude IRQ from balancing if requested */
        #不用设置irq balance
        if (new->flags & IRQF_NOBALANCING) {
            irq_settings_set_no_balancing(desc);
            irqd_set(&desc->irq_data, IRQD_NO_BALANCING);
        }
        #开始中断
        if (irq_settings_can_autoenable(desc)) {
            irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
        } else {
            /*
             * Shared interrupts do not go well with disabling
             * auto enable. The sharing interrupt might request
             * it while it's still disabled and then wait for
             * interrupts forever.
             */
            WARN_ON_ONCE(new->flags & IRQF_SHARED);
            /* Undo nested disables: */
            desc->depth = ;
        }  
 
    } else if (new->flags & IRQF_TRIGGER_MASK) {
        unsigned int nmsk = new->flags & IRQF_TRIGGER_MASK;
        unsigned int omsk = irqd_get_trigger_type(&desc->irq_data);  
 
        if (nmsk != omsk)
            /* hope the handler works with current  trigger mode */
            pr_warn("irq %d uses trigger mode %u; requested %u\n",
                irq, omsk, nmsk);
    }  
 
    *old_ptr = new;
    #设置power相关
    irq_pm_install_action(desc, new);  
 
    /* Reset broken irq detection when installing new handler */
    desc->irq_count = ;
    desc->irqs_unhandled = ;  
 
    /*
     * Check whether we disabled the irq via the spurious handler
     * before. Reenable it and give it another chance.
     */
    if (shared && (desc->istate & IRQS_SPURIOUS_DISABLED)) {
        desc->istate &= ~IRQS_SPURIOUS_DISABLED;
        __enable_irq(desc);
    }  
 
    raw_spin_unlock_irqrestore(&desc->lock, flags);
    chip_bus_sync_unlock(desc);
    mutex_unlock(&desc->request_mutex);  
 
    irq_setup_timings(desc, new);  
 
    /*
     * Strictly no need to wake it up, but hung_task complains
     * when no hard interrupt wakes the thread up.
     */
    # 如果有中断线程的话，则wakeup线程
    if (new->thread)
        wake_up_process(new->thread);
    if (new->secondary)
        wake_up_process(new->secondary->thread);
    #注册irq在proc中的接口
    register_irq_proc(irq, desc);
    new->dir = NULL;
    register_handler_proc(irq, new);
    return ;  
 
mismatch:
    if (!(new->flags & IRQF_PROBE_SHARED)) {
        pr_err("Flags mismatch irq %d. %08x (%s) vs. %08x (%s)\n",
               irq, new->flags, new->name, old->flags, old->name);
#ifdef CONFIG_DEBUG_SHIRQ
        dump_stack();
#endif
    }
    ret = -EBUSY;
#一下都是异常case
out_unlock:
    raw_spin_unlock_irqrestore(&desc->lock, flags);  
 
    if (!desc->action)
        irq_release_resources(desc);
out_bus_unlock:
    chip_bus_sync_unlock(desc);
    mutex_unlock(&desc->request_mutex);  
 
out_thread:
    if (new->thread) {
        struct task_struct *t = new->thread;  
 
        new->thread = NULL;
        kthread_stop(t);
        put_task_struct(t);
    }
    if (new->secondary && new->secondary->thread) {
        struct task_struct *t = new->secondary->thread;  
 
        new->secondary->thread = NULL;
        kthread_stop(t);
        put_task_struct(t);
    }
out_mput:
    module_put(desc->owner);
    return ret;
}  

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/tiantao2012/article/details/78957472

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1. int setup_irq(unsigned int irq, struct irqaction *act)用于设置irq对应的irqaction.
2. 其使用的例程如下：
3. struct irq_domain * __init __init_i8259_irqs(struct device_node *node)
4. {
5. struct irq_domain *domain;
6. insert_resource(&ioport_resource, &pic1_io_resource);
7. insert_resource(&ioport_resource, &pic2_io_resource);
8. init_8259A(0);
9. domain = irq_domain_add_legacy(node, 16, I8259A_IRQ_BASE, 0,
10. &i8259A_ops, NULL);
11. if (!domain)
12. panic("Failed to add i8259 IRQ domain");
13. setup_irq(I8259A_IRQ_BASE + PIC_CASCADE_IR, &irq2);
14. return domain;
15. }
16. 其源码分析如下：
17. int setup_irq(unsigned int irq, struct irqaction *act)
18. {
19. int retval;
20. struct irq_desc *desc = irq_to_desc(irq);
21. #中断描述为null，或者设置了_IRQ_PER_CPU_DEVID 标志的话，则直接退出
22. if (!desc || WARN_ON(irq_settings_is_per_cpu_devid(desc)))
23. return -EINVAL;
24. retval = irq_chip_pm_get(&desc->irq_data);
25. if (retval < 0)
26. return retval;
27. #核心代码，设置irq对应的irqaction *act
28. retval = __setup_irq(irq, desc, act);
29. if (retval)
30. irq_chip_pm_put(&desc->irq_data);
31. return retval;
32. }
33. static int
34. __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
35. {
36. struct irqaction *old, **old_ptr;
37. unsigned long flags, thread_mask = 0;
38. int ret, nested, shared = 0;
39. #中断描述符为null，则退出
40. if (!desc)
41. return -EINVAL;
42. #没有设置irq_data.chip，所以irq_data.chip 会等于no_irq_chip。这属于异常case ，退出.
43. if (desc->irq_data.chip == &no_irq_chip)
44. return -ENOSYS;
45. #增加这个模块的引用计数
46. if (!try_module_get(desc->owner))
47. return -ENODEV;
48. #更新struct irqaction *new 中的irq number
49. new->irq = irq;
50. /*
51. * If the trigger type is not specified by the caller,
52. * then use the default for this interrupt.
53. */
54. #没有设置中断触发类型的话，则用默认值.
55. if (!(new->flags & IRQF_TRIGGER_MASK))
56. new->flags |= irqd_get_trigger_type(&desc->irq_data);
57. /*
58. * Check whether the interrupt nests into another interrupt
59. * thread.
60. */
61. #检查这里是否是中断嵌套，正常情况下irq_chip 基本都不支持中断嵌套
62. nested = irq_settings_is_nested_thread(desc);
63. if (nested) {
64. if (!new->thread_fn) {
65. ret = -EINVAL;
66. goto out_mput;
67. }
68. /*
69. * Replace the primary handler which was provided from
70. * the driver for non nested interrupt handling by the
71. * dummy function which warns when called.
72. */
73. new->handler = irq_nested_primary_handler;
74. } else {
75. #这里检查是否为这个中断设置一个thread，也就是说是否支持中断线程化
76. if (irq_settings_can_thread(desc)) {
77. ret = irq_setup_forced_threading(new);
78. if (ret)
79. goto out_mput;
80. }
81. }
82. /*
83. * Create a handler thread when a thread function is supplied
84. * and the interrupt does not nest into another interrupt
85. * thread.
86. */
87. #在没有支持中断嵌套且用户用设置中断线程的情况下,这里会创建一个中断线程
88. if (new->thread_fn && !nested) {
89. ret = setup_irq_thread(new, irq, false);
90. if (ret)
91. goto out_mput;
92. #中断线程化时是否支持第二个线程。如果支持的话，再创建一个中断线程.
93. if (new->secondary) {
94. ret = setup_irq_thread(new->secondary, irq, true);
95. if (ret)
96. goto out_thread;
97. }
98. }
99. /*
100. * Drivers are often written to work w/o knowledge about the
101. * underlying irq chip implementation, so a request for a
102. * threaded irq without a primary hard irq context handler
103. * requires the ONESHOT flag to be set. Some irq chips like
104. * MSI based interrupts are per se one shot safe. Check the
105. * chip flags, so we can avoid the unmask dance at the end of
106. * the threaded handler for those.
107. */
108. #有设置oneshot 标志的话，则清掉这个标志.
109. if (desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)
110. new->flags &= ~IRQF_ONESHOT;
111. /*
112. * Protects against a concurrent __free_irq() call which might wait
113. * for synchronize_irq() to complete without holding the optional
114. * chip bus lock and desc->lock.
115. */
116. mutex_lock(&desc->request_mutex);
117. /*
118. * Acquire bus lock as the irq_request_resources() callback below
119. * might rely on the serialization or the magic power management
120. * functions which are abusing the irq_bus_lock() callback,
121. */
122. chip_bus_lock(desc);
123. /* First installed action requests resources. */
124. #中断描述符的action为null的话，则通过irq_request_resources 来申请中断资源.
125. if (!desc->action) {
126. ret = irq_request_resources(desc);
127. if (ret) {
128. pr_err("Failed to request resources for %s (irq %d) on irqchip %s\n",
129. new->name, irq, desc->irq_data.chip->name);
130. goto out_bus_unlock;
131. }
132. }
133. /*
134. * The following block of code has to be executed atomically
135. * protected against a concurrent interrupt and any of the other
136. * management calls which are not serialized via
137. * desc->request_mutex or the optional bus lock.
138. */
139. raw_spin_lock_irqsave(&desc->lock, flags);
140. old_ptr = &desc->action;
141. old = *old_ptr;
142. #如果这个中断号对应的中断描述符中的action 不为null，说明这个中断号之前可能已经申请过中断了
143. #这里同样可以得出结论，同一个中断好，可以重复申请中断，但是可能会继承前一次的中断触发类型.
144. if (old) {
145. /*
146. * Can't share interrupts unless both agree to and are
147. * the same type (level, edge, polarity). So both flag
148. * fields must have IRQF_SHARED set and the bits which
149. * set the trigger type must match. Also all must
150. * agree on ONESHOT.
151. */
152. unsigned int oldtype;
153. /*
154. * If nobody did set the configuration before, inherit
155. * the one provided by the requester.
156. */
157. if (irqd_trigger_type_was_set(&desc->irq_data)) {
158. oldtype = irqd_get_trigger_type(&desc->irq_data);
159. } else {
160. oldtype = new->flags & IRQF_TRIGGER_MASK;
161. irqd_set_trigger_type(&desc->irq_data, oldtype);
162. }
163. if (!((old->flags & new->flags) & IRQF_SHARED) ||
164. (oldtype != (new->flags & IRQF_TRIGGER_MASK)) ||
165. ((old->flags ^ new->flags) & IRQF_ONESHOT))
166. goto mismatch;
167. /* All handlers must agree on per-cpuness */
168. if ((old->flags & IRQF_PERCPU) !=
169. (new->flags & IRQF_PERCPU))
170. goto mismatch;
171. /* add new interrupt at end of irq queue */
172. do {
173. /*
174. * Or all existing action->thread_mask bits,
175. * so we can find the next zero bit for this
176. * new action.
177. */
178. thread_mask |= old->thread_mask;
179. old_ptr = &old->next;
180. old = *old_ptr;
181. } while (old);
182. shared = 1;
183. }
184. /*
185. * Setup the thread mask for this irqaction for ONESHOT. For
186. * !ONESHOT irqs the thread mask is 0 so we can avoid a
187. * conditional in irq_wake_thread().
188. */
189. if (new->flags & IRQF_ONESHOT) {
190. /*
191. * Unlikely to have 32 resp 64 irqs sharing one line,
192. * but who knows.
193. */
194. if (thread_mask == ~0UL) {
195. ret = -EBUSY;
196. goto out_unlock;
197. }
198. /*
199. * The thread_mask for the action is or'ed to
200. * desc->thread_active to indicate that the
201. * IRQF_ONESHOT thread handler has been woken, but not
202. * yet finished. The bit is cleared when a thread
203. * completes. When all threads of a shared interrupt
204. * line have completed desc->threads_active becomes
205. * zero and the interrupt line is unmasked. See
206. * handle.c:irq_wake_thread() for further information.
207. *
208. * If no thread is woken by primary (hard irq context)
209. * interrupt handlers, then desc->threads_active is
210. * also checked for zero to unmask the irq line in the
211. * affected hard irq flow handlers
212. * (handle_[fasteoi|level]_irq).
213. *
214. * The new action gets the first zero bit of
215. * thread_mask assigned. See the loop above which or's
216. * all existing action->thread_mask bits.
217. */
218. new->thread_mask = 1UL << ffz(thread_mask);
219. } else if (new->handler == irq_default_primary_handler &&
220. !(desc->irq_data.chip->flags & IRQCHIP_ONESHOT_SAFE)) {
221. /*
222. * The interrupt was requested with handler = NULL, so
223. * we use the default primary handler for it. But it
224. * does not have the oneshot flag set. In combination
225. * with level interrupts this is deadly, because the
226. * default primary handler just wakes the thread, then
227. * the irq lines is reenabled, but the device still
228. * has the level irq asserted. Rinse and repeat....
229. *
230. * While this works for edge type interrupts, we play
231. * it safe and reject unconditionally because we can't
232. * say for sure which type this interrupt really
233. * has. The type flags are unreliable as the
234. * underlying chip implementation can override them.
235. */
236. pr_err("Threaded irq requested with handler=NULL and !ONESHOT for irq %d\n",
237. irq);
238. ret = -EINVAL;
239. goto out_unlock;
240. }
241. #非共享中断
242. if (!shared) {
243. #初始化一个等待队列，这个等待队列包含在中断描述符中
244. init_waitqueue_head(&desc->wait_for_threads);
245. /* Setup the type (level, edge polarity) if configured: */
246. if (new->flags & IRQF_TRIGGER_MASK) {
247. ret = __irq_set_trigger(desc,
248. new->flags & IRQF_TRIGGER_MASK);
249. if (ret)
250. goto out_unlock;
251. }
252. /*
253. * Activate the interrupt. That activation must happen
254. * independently of IRQ_NOAUTOEN. request_irq() can fail
255. * and the callers are supposed to handle
256. * that. enable_irq() of an interrupt requested with
257. * IRQ_NOAUTOEN is not supposed to fail. The activation
258. * keeps it in shutdown mode, it merily associates
259. * resources if necessary and if that's not possible it
260. * fails. Interrupts which are in managed shutdown mode
261. * will simply ignore that activation request.
262. */
263. #激活这个中断
264. ret = irq_activate(desc);
265. if (ret)
266. goto out_unlock;
267. desc->istate &= ~(IRQS_AUTODETECT | IRQS_SPURIOUS_DISABLED | \
268. IRQS_ONESHOT | IRQS_WAITING);
269. irqd_clear(&desc->irq_data, IRQD_IRQ_INPROGRESS);
270. #是不是percpu中断
271. if (new->flags & IRQF_PERCPU) {
272. irqd_set(&desc->irq_data, IRQD_PER_CPU);
273. irq_settings_set_per_cpu(desc);
274. }
275. if (new->flags & IRQF_ONESHOT)
276. desc->istate |= IRQS_ONESHOT;
277. /* Exclude IRQ from balancing if requested */
278. #不用设置irq balance
279. if (new->flags & IRQF_NOBALANCING) {
280. irq_settings_set_no_balancing(desc);
281. irqd_set(&desc->irq_data, IRQD_NO_BALANCING);
282. }
283. #开始中断
284. if (irq_settings_can_autoenable(desc)) {
285. irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
286. } else {
287. /*
288. * Shared interrupts do not go well with disabling
289. * auto enable. The sharing interrupt might request
290. * it while it's still disabled and then wait for
291. * interrupts forever.
292. */
293. WARN_ON_ONCE(new->flags & IRQF_SHARED);
294. /* Undo nested disables: */
295. desc->depth = 1;
296. }
297. } else if (new->flags & IRQF_TRIGGER_MASK) {
298. unsigned int nmsk = new->flags & IRQF_TRIGGER_MASK;
299. unsigned int omsk = irqd_get_trigger_type(&desc->irq_data);
300. if (nmsk != omsk)
301. /* hope the handler works with current  trigger mode */
302. pr_warn("irq %d uses trigger mode %u; requested %u\n",
303. irq, omsk, nmsk);
304. }
305. *old_ptr = new;
306. #设置power相关
307. irq_pm_install_action(desc, new);
308. /* Reset broken irq detection when installing new handler */
309. desc->irq_count = 0;
310. desc->irqs_unhandled = 0;
311. /*
312. * Check whether we disabled the irq via the spurious handler
313. * before. Reenable it and give it another chance.
314. */
315. if (shared && (desc->istate & IRQS_SPURIOUS_DISABLED)) {
316. desc->istate &= ~IRQS_SPURIOUS_DISABLED;
317. __enable_irq(desc);
318. }
319. raw_spin_unlock_irqrestore(&desc->lock, flags);
320. chip_bus_sync_unlock(desc);
321. mutex_unlock(&desc->request_mutex);
322. irq_setup_timings(desc, new);
323. /*
324. * Strictly no need to wake it up, but hung_task complains
325. * when no hard interrupt wakes the thread up.
326. */
327. # 如果有中断线程的话，则wakeup线程
328. if (new->thread)
329. wake_up_process(new->thread);
330. if (new->secondary)
331. wake_up_process(new->secondary->thread);
332. #注册irq在proc中的接口
333. register_irq_proc(irq, desc);
334. new->dir = NULL;
335. register_handler_proc(irq, new);
336. return 0;
337. mismatch:
338. if (!(new->flags & IRQF_PROBE_SHARED)) {
339. pr_err("Flags mismatch irq %d. %08x (%s) vs. %08x (%s)\n",
340. irq, new->flags, new->name, old->flags, old->name);
341. #ifdef CONFIG_DEBUG_SHIRQ
342. dump_stack();
343. #endif
344. }
345. ret = -EBUSY;
346. #一下都是异常case
347. out_unlock:
348. raw_spin_unlock_irqrestore(&desc->lock, flags);
349. if (!desc->action)
350. irq_release_resources(desc);
351. out_bus_unlock:
352. chip_bus_sync_unlock(desc);
353. mutex_unlock(&desc->request_mutex);
354. out_thread:
355. if (new->thread) {
356. struct task_struct *t = new->thread;
357. new->thread = NULL;
358. kthread_stop(t);
359. put_task_struct(t);
360. }
361. if (new->secondary && new->secondary->thread) {
362. struct task_struct *t = new->secondary->thread;
363. new->secondary->thread = NULL;
364. kthread_stop(t);
365. put_task_struct(t);
366. }
367. out_mput:
368. module_put(desc->owner);
369. return ret;
370. }