linux SPI驱动——spidev之driver（六）
一： spidev_init注册spidev
1: static int __init spidev_init(void)
2: {
3: int status;
4:
5: /* Claim our 256 reserved device numbers. Then register a class
6: * that will key udev/mdev to add/remove /dev nodes. Last, register
7: * the driver which manages those device numbers.
8: */
9: BUILD_BUG_ON(N_SPI_MINORS > 256);
10: /* 注册spi字符设备 */
11: status = register_chrdev(SPIDEV_MAJOR, "spi", &spidev_fops);
12: if (status < 0) {
13: return status;
14: }
15: /* 为该设备创建一个class spidev */
16: spidev_class = class_create(THIS_MODULE, "spidev");
17: if (IS_ERR(spidev_class)) {
18: unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
19: return PTR_ERR(spidev_class);
20: }
21: /* register匹配到device ,最终调用prob函数 */
22: status = spi_register_driver(&spidev_spi_driver);
23: if (status < 0) {
24: class_destroy(spidev_class);
25: unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
26: }
27: return status;
28: }
29: module_init(spidev_init);
30:
31: static void __exit spidev_exit(void)
32: {
33: spi_unregister_driver(&spidev_spi_driver);
34: class_destroy(spidev_class);
35: unregister_chrdev(SPIDEV_MAJOR, spidev_spi_driver.driver.name);
36: }
37: module_exit(spidev_exit);
38:
39: MODULE_AUTHOR("Andrea Paterniani, <a.paterniani@swapp-eng.it>");
40: MODULE_DESCRIPTION("User mode SPI device interface");
41: MODULE_LICENSE("GPL");
42: MODULE_ALIAS("spi:spidev");
总结：
1)注册一个字符设备，cat /proc/device 会查看到“153 spi”主设备号位153的设备
2) 创建一个class spidev ，”/sys/class/spidev/”
3) spi_register_driver 注册spi driver。
二：spidev_probe 函数
1: static int __devinit spidev_probe(struct spi_device *spi)
2: {
3: struct spidev_data *spidev;
4: int status;
5: unsigned long minor;
6:
7: /* Allocate driver data */
8: spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
9: if (!spidev)
10: return -ENOMEM;
11:
12: /* Initialize the driver data */
13: spidev->spi = spi;
14: spin_lock_init(&spidev->spi_lock);
15: mutex_init(&spidev->buf_lock);
16:
17: INIT_LIST_HEAD(&spidev->device_entry);
18:
19: /* If we can allocate a minor number, hook up this device.
20: * Reusing minors is fine so long as udev or mdev is working.
21: */
22: mutex_lock(&device_list_lock);
23:
24: minor = find_first_zero_bit(minors, N_SPI_MINORS);
25: if (minor < N_SPI_MINORS) {
26: struct device *dev;
27:
28: spidev->devt = MKDEV(SPIDEV_MAJOR, minor);
29: dev = device_create(spidev_class, &spi->dev, spidev->devt,
30: spidev, "spidev%d.%d",
31: spi->master->bus_num, spi->chip_select);
32: status = IS_ERR(dev) ? PTR_ERR(dev) : 0;
33: } else {
34: dev_dbg(&spi->dev, "no minor number available!\n");
35: status = -ENODEV;
36: }
37: if (status == 0) {
38: set_bit(minor, minors);
39: list_add(&spidev->device_entry, &device_list);
40: }
41:
42: mutex_unlock(&device_list_lock);
43:
44: if (status == 0)
45: spi_set_drvdata(spi, spidev);
46: else
47: kfree(spidev);
48:
49: return status;
50: }
总结： 1. spidev_prob函数很简单，调用device_create创界字符设备的结点名为"spidev%d.%d" 2. 将spidev作为spi->dev->p->driver_data 的data
三：spidev_probe 函数是如何被调用的，以及什么时候被调用的追踪 status = spi_register_driver(&spidev_spi_driver)调用
1: int spi_register_driver(struct spi_driver *sdrv)
2: {
3: sdrv->driver.bus = &spi_bus_type;
4: if (sdrv->probe)
5: sdrv->driver.probe = spi_drv_probe;
6: if (sdrv->remove)
7: sdrv->driver.remove = spi_drv_remove;
8: if (sdrv->shutdown)
9: sdrv->driver.shutdown = spi_drv_shutdown;
10: return driver_register(&sdrv->driver);
11: }
//sdrv->driver.probe = spi_drv_probe; 函数
1: static int spi_drv_probe(struct device *dev)
2: {
3: const struct spi_driver *sdrv = to_spi_driver(dev->driver);
4:
5: return sdrv->probe(to_spi_device(dev));
6: }
可以看出调用spi_drv_prob就是调用sdrv->probe，即spidev_probe 函数
2）追踪driver_register(&sdrv->driver);
1: int driver_register(struct device_driver *drv)
2: {
3: int ret;
4: struct device_driver *other;
5:
6: BUG_ON(!drv->bus->p);
7:
8: if ((drv->bus->probe && drv->probe) ||
9: (drv->bus->remove && drv->remove) ||
10: (drv->bus->shutdown && drv->shutdown))
11: printk(KERN_WARNING "Driver '%s' needs updating - please use "
12: "bus_type methods\n", drv->name);
13:
14: other = driver_find(drv->name, drv->bus);
15: if (other) {
16: put_driver(other);
17: printk(KERN_ERR "Error: Driver '%s' is already registered, "
18: "aborting...\n", drv->name);
19: return -EBUSY;
20: }
21:
22: ret = bus_add_driver(drv);
23: if (ret)
24: return ret;
25: ret = driver_add_groups(drv, drv->groups);
26: if (ret)
27: bus_remove_driver(drv);
28: return ret;
29: }
查看bus_add_driver(drv)函数调用，有一段代码
1: if (drv->bus->p->drivers_autoprobe) {
2: error = driver_attach(drv);
3: if (error) 4: goto out_unregister;
5: }
再看一下driver_attach函数
1: int driver_attach(struct device_driver *drv)
2: {
3: return bus_for_each_dev(drv->bus, NULL, drv, __driver_attach);
4: }
1: int bus_for_each_dev(struct bus_type *bus, struct device *start,
2: void *data, int (*fn)(struct device *, void *))
3: {
4: struct klist_iter i;
5: struct device *dev;
6: int error = 0;
7:
8: if (!bus)
9: return -EINVAL;
10:
11: klist_iter_init_node(&bus->p->klist_devices, &i,
12: (start ? &start->p->knode_bus : NULL));
13: while ((dev = next_device(&i)) && !error)
14: error = fn(dev, data);
15: klist_iter_exit(&i);
16: return error;
17: }
从上面两段代码可以看出bus_for_each_dev会遍历总线上所有设备并设用__driver_attach。我们再看一下__driver_attach所做的工作：
1.driver_match_device(drv, dev)；device与driver name时候strncmp
2.driver_probe_device(drv, dev); 函数调用prob
1: static int __driver_attach(struct device *dev, void *data)
2: {
3: struct device_driver *drv = data;
4:
5:
6: if (!driver_match_device(drv, dev))
7: return 0;
8:
9: if (dev->parent) /* Needed for USB */
10: device_lock(dev->parent);
11: device_lock(dev);
12: if (!dev->driver)
13: driver_probe_device(drv, dev);
14: device_unlock(dev);
15: if (dev->parent)
16: device_unlock(dev->parent);
17:
18: return 0;
19: }
我们再继续查看一下driver_probe_device函数的调用：
1: int driver_probe_device(struct device_driver *drv, struct device *dev)
2: {
3: int ret = 0;
4:
5: if (!device_is_registered(dev))
6: return -ENODEV;
7:
8: pr_debug("bus: '%s': %s: matched device %s with driver %s\n",
9: drv->bus->name, __func__, dev_name(dev), drv->name);
10:
11: pm_runtime_get_noresume(dev);
12: pm_runtime_barrier(dev);
13:
ret = really_probe(dev, drv);
14: pm_runtime_put_sync(dev);
15:
16: return ret;
17: }
总结 : 通过代码最终我们最终看到了spidev_prob函数是怎样被调用的
