i2c子系统

490 if (drv->shutdown)
491 drv->driver.shutdown = platform_drv_shutdown;
}> 492
493 return driver_register(&drv->driver);
494 }
486和487
ARRAY_SIZE(msm_camera_boardinfo));
这个函数主要是把i2c 的外围设备信息结构体struct ic2_board_info 分装进struct i2c_devinfo结构，再把这个结构放到__i2c_board_list这个链表上。
该函数的第一个参数其实是该i2c 设备所属的adapter的编号，不同的adapter使用的低层i2c通信协议算法可能不一样。
794 {
795 return platform_driver_register(&msm_i2c_driver);
796 }
platform_driver_register(&msm_i2c_driver) 的过程和platform_device_register的过程很相似，主要两部还是match和probe，不过这回platform_bus_type上已经有设备了，它回去probe设备，并最终调用platform_driver的probe函数msm_i2c_probe。我们来看一看该函数做了些什么。
platform_device的注册过程不详细讲述了，只讲一下最重要的两部match和probe:
a、match
drivers/base/base.h
120 static inline int driver_match_device(struct device_driver *drv,
121 struct device *dev)
platform_device->name和device_driver->name
b、probe
static int really_probe(struct device *dev, struct device_driver *drv)
120 if (dev->bus->probe) {
121 ret = dev->bus->probe(dev);
122 if (ret)
123 goto probe_failed;
124 } else if (drv->probe) {
125 ret = drv->probe(dev);
126 if (ret)
127 goto probe_failed;
pdev->name);
if (!ioarea) {
dev_err(&pdev->dev, "I2C region already claimed\n");
return -EBUSY;
}
clk = clk_get(&pdev->dev, "i2c_clk");
if (IS_ERR(clk)) {
672 {
673 struct platform_device *pdev = to_platform_device(dev);
674 struct platform_driver *pdrv = to_platform_driver(drv);
675
676 /* match against the id table first */
128 }
这里先看能不能call bus->probe，不能则call devices_driver->probe
483 int platform_driver_register(struct platform_driver *drv)
484 {
485 drv->driver.bus = &platform_bus_type;
......
}
(1) 在此处注册了很多的platform_device devices[]，在这一堆的platform_devices中有
msm_device_i2c,
msm_device_i2c_2,
这样两个设备(具体的区别还没有弄清楚，有可能是该板子有两条i2c总线)，它们其实就是很容易被人们遗忘的i2c controler，它们被当作platform_device在板子初始化时进行注册。
......
(2) msm_device_i2c_init();
msm_device_i2c_2_init();
......
(3) i2c_register_board_info(4 /* QUP ID */, msm_camera_boardinfo,
ARRAY_SIZE(msm_camera_boardinfo));
static int
msm_i2c_probe(struct platform_device *pdev)
{
......
mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!mem) {
dev_err(&pdev->dev, "no mem resource?\n");
2、i2c controler driver 的加载过程
drivers/i2c/busses/i2c-msm.c 该文件就是i2c controler的驱动程序。
780 static struct platform_driver msm_i2c_driver = {
781 .probe = msm_i2c_probe,
486 if (drv->probe)
'> 487 drv->driver.probe = platform_drv_probe;
488 if (drv->remove)
489 drv->driver.remove = platform_drv_remove;
122 {
)>123 return drv->bus->match ? drv->bus->match(dev, drv) : 1;
124 }
call bus->match
671 static int platform_match(struct device *dev, struct device_driver *drv)
i2c subsystem的故事还要从很久以前说起，那是一个混沌初开的年代......
1、板子初始化
arch/arm/mach-msm/board-msm7x30.c
static void __init msm7x30_init(void)
{
......
(1) platform_add_devices(devices, ARRAY_SIZE(devices));
646 struct platform_device *pdev)
647 {
648 while (id->(pdev->name, id->name) == 0) { platform_driver有可能支持多个platform_device，所以可能会有多个platform_device_id项
pr_err("failed to request I2C gpios\n");
msm_device_i2c.dev.platform_data = &msm_i2c_pdata;
}
主要是gpio的申请和i2c controler 平台数据的赋值。
(3)i2c_register_board_info(4 /* QUP ID */, msm_camera_boardinfo,
dev_err(&pdev->dev, "Could not get clock\n");
ret = PTR_ERR(clk);
goto err_clk_get_failed;
}
pdata = pdev->dev.platform_data;
if (!pdata) {
dev_err(&pdev->dev, "platform data not initialized\n");
677 if (pdrv->id_table)
678 return platform_match_id(pdrv->id_table, pdev) != NULL;
679
680 /* fall-back to driver name match */
681 return (strcmp(pdev->name, drv->name) == 0);
return -ENODEV;
}
irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
if (!irq) {
dev_err(&pdev->dev, "no irq resource?\n");
return -ENODEV;
}
ioarea = request_mem_region(mem->start, (mem->end - mem->start) + 1,
682 }
首先看platform_driver有没有定义id_table，有的话：
644 static const struct platform_device_id *platform_match_id(