init/main.c:
1 asmlinkage void start_kernel(void) 2 { 3 ...... 4 early_irq_init(); 5 init_IRQ(); 6 ...... 7 }
early_irq_init()函数有两种实现，一种是基于radix tree，一种是定义静态数组，如果要使用radix tree实现的，那么需要打开SPARSE_IRQ配置选项，由于我对数据结构不了解，所以分析以下静态数组实现方式版本的。
/kernel/irq/irqdesc.c
1 struct irq_desc irq_desc[NR_IRQS] __cacheline_aligned_in_smp = { 2 [0 ... NR_IRQS-1] = { 3 .handle_irq = handle_bad_irq, 4 .depth = 1, 5 .lock = __RAW_SPIN_LOCK_UNLOCKED(irq_desc->lock), 6 } 7 }; 8 9 int __init early_irq_init(void) 10 { 11 int count, i, node = first_online_node; 12 struct irq_desc *desc; 13 14 init_irq_default_affinity(); 15 16 printk(KERN_INFO "NR_IRQS:%d ", NR_IRQS); 17 18 desc = irq_desc; 19 count = ARRAY_SIZE(irq_desc); 20 21 for (i = 0; i < count; i++) { 22 desc[i].kstat_irqs = alloc_percpu(unsigned int); 23 alloc_masks(&desc[i], GFP_KERNEL, node); 24 raw_spin_lock_init(&desc[i].lock); 25 lockdep_set_class(&desc[i].lock, &irq_desc_lock_class); 26 desc_set_defaults(i, &desc[i], node); 27 } 28 return arch_early_irq_init(); 29 }
第一次见到这种初始化数组全部成员为同样内容的方式，可以学习积累下。
NR_IRQS在arch/arm/mach-s5pv210/include/mach/irqs.h下定义：
1 #define NR_IRQS (IRQ_EINT(31) + S5P_GPIOINT_COUNT + 1)
上面函数的核心就是调用desc_set_defaults()来初始化上述中断描述符数组，kernel/irq/irqdesc.c:
1 static void desc_set_defaults(unsigned int irq, struct irq_desc *desc, int node) 2 { 3 int cpu; 4 5 desc->irq_data.irq = irq; 6 desc->irq_data.chip = &no_irq_chip; 7 desc->irq_data.chip_data = NULL; 8 desc->irq_data.handler_data = NULL; 9 desc->irq_data.msi_desc = NULL; 10 irq_settings_clr_and_set(desc, ~0, _IRQ_DEFAULT_INIT_FLAGS); 11 irqd_set(&desc->irq_data, IRQD_IRQ_DISABLED); 12 desc->handle_irq = handle_bad_irq; 13 desc->depth = 1; 14 desc->irq_count = 0; 15 desc->irqs_unhandled = 0; 16 desc->name = NULL; 17 for_each_possible_cpu(cpu) 18 *per_cpu_ptr(desc->kstat_irqs, cpu) = 0; 19 desc_smp_init(desc, node); 20 }
最后返回时调用的arch_early_irq_init()函数并没有做事情。
接着看init_IRQ():
1 void __init init_IRQ(void) 2 { 3 machine_desc->init_irq(); 4 }
machine_desc是全局变量，定义在板文件中，由于我们使用的是s5pv210，且demo板号选的是smdkv210，所以这个全局变量就在arch/arm/mach-s5pv210/mach-s5pv210.c中：
1 MACHINE_START(SMDKV210, "SMDKV210") 2 /* Maintainer: Kukjin Kim <kgene.kim@samsung.com> */ 3 .boot_params = S5P_PA_SDRAM + 0x100, 4 .init_irq = s5pv210_init_irq, 5 .map_io = smdkv210_map_io, 6 .init_machine = smdkv210_machine_init, 7 .timer = &s5p_timer, 8 MACHINE_END
arch/arm/mach-s5pv210/mach-s5pv210.c中还有如下函数定义：
1 void __init s5pv210_init_irq(void) 2 { 3 u32 vic[4]; /* S5PV210 supports 4 VIC */ 4 5 /* All the VICs are fully populated. */ 6 vic[0] = ~0; 7 vic[1] = ~0; 8 vic[2] = ~0; 9 vic[3] = ~0; 10 11 s5p_init_irq(vic, ARRAY_SIZE(vic)); 12 }
arch/arm/plat-s5p/irq.c
1 void __init s5p_init_irq(u32 *vic, u32 num_vic) 2 { 3 #ifdef CONFIG_ARM_VIC 4 int irq; 5 6 /* initialize the VICs */ 7 for (irq = 0; irq < num_vic; irq++) 8 vic_init(VA_VIC(irq), VIC_BASE(irq), vic[irq], 0); 9 #endif 10 11 s3c_init_vic_timer_irq(5, IRQ_TIMER0); 12 13 s3c_init_uart_irqs(uart_irqs, ARRAY_SIZE(uart_irqs)); 14 }
上面涉及到的函数都是去操作VIC相关的寄存器，这部分操作还不是很清楚，先不往下继续追踪了。