上一此说到了驱动和设备匹配,中间隔了几天读了下 LDD3 ch14: The Linux Device Model,受益匪浅。
平台驱动中添加 .id_table 成员好处是 使驱动和设备可以一对多,即一个驱动可以支持多个设备。如果我们只使用设备里的 name 和驱动里的name进行匹配匹配那么设备和驱动只能一对一了。
static struct platform_device_id s3c24xx_driver_ids[] = { { .name = "s3c2410-i2c", .driver_data = TYPE_S3C2410, }, { .name = "s3c2440-i2c", .driver_data = TYPE_S3C2440, }, { }, };
关于设备和驱动匹配后如何绑定的我们来继续分析代码
static int __driver_attach(struct device *dev, void *data) { struct device_driver *drv = data; /* * Lock device and try to bind to it. We drop the error * here and always return 0, because we need to keep trying * to bind to devices and some drivers will return an error * simply if it didn't support the device. * * driver_probe_device() will spit a warning if there * is an error. */ if (!driver_match_device(drv, dev)) //匹配 return 0; if (dev->parent) /* Needed for USB */ device_lock(dev->parent); device_lock(dev); if (!dev->driver) driver_probe_device(drv, dev); //绑定 device_unlock(dev); if (dev->parent) device_unlock(dev->parent); return 0; }
上节分析到 在
driver_match_device(drv, dev)
中完成了驱动和设备的匹配, 向下看 driver_probe_device(drv, dev) 函数 注释上写了 试图把设备和驱动绑定到一起。呵呵,像月老用红绳把痴男怨女的脚绑到一起,才突然明白为什么这么多年轻人手上面系着红绳。
/** * driver_probe_device - attempt to bind device & driver together * @drv: driver to bind a device to * @dev: device to try to bind to the driver * * This function returns -ENODEV if the device is not registered, * 1 if the device is bound successfully and 0 otherwise. * * This function must be called with @dev lock held. When called for a * USB interface, @dev->parent lock must be held as well. */ int driver_probe_device(struct device_driver *drv, struct device *dev) { int ret = 0; if (!device_is_registered(dev)) return -ENODEV; pr_debug("bus: '%s': %s: matched device %s with driver %s\n", drv->bus->name, __func__, dev_name(dev), drv->name); pm_runtime_get_noresume(dev); pm_runtime_barrier(dev); ret = really_probe(dev, drv); pm_runtime_put_sync(dev); return ret; }
继续分析里面有个 real_probe(dev, drv) 函数
static int really_probe(struct device *dev, struct device_driver *drv) { int ret = 0; atomic_inc(&probe_count); pr_debug("bus: '%s': %s: probing driver %s with device %s\n", drv->bus->name, __func__, drv->name, dev_name(dev)); WARN_ON(!list_empty(&dev->devres_head)); dev->driver = drv; //呵呵 终于看到了 if (driver_sysfs_add(dev)) { printk(KERN_ERR "%s: driver_sysfs_add(%s) failed\n", __func__, dev_name(dev)); goto probe_failed; } if (dev->bus->probe) { ret = dev->bus->probe(dev); if (ret) goto probe_failed; } else if (drv->probe) { ret = drv->probe(dev); if (ret) goto probe_failed; } driver_bound(dev); ret = 1; pr_debug("bus: '%s': %s: bound device %s to driver %s\n", drv->bus->name, __func__, dev_name(dev), drv->name); goto done; probe_failed: devres_release_all(dev); driver_sysfs_remove(dev); dev->driver = NULL; if (ret != -ENODEV && ret != -ENXIO) { /* driver matched but the probe failed */ printk(KERN_WARNING "%s: probe of %s failed with error %d\n", drv->name, dev_name(dev), ret); } /* * Ignore errors returned by ->probe so that the next driver can try * its luck. */ ret = 0; done: atomic_dec(&probe_count); wake_up(&probe_waitqueue); return ret; }
看到一行 dev->driver = drv, 这样应该就是把设备结构里的驱动指向了 我们注册的 driver。那下面为什么还有一行driver_bound(dev),看样还要继续分析。
static void driver_bound(struct device *dev) { if (klist_node_attached(&dev->p->knode_driver)) { printk(KERN_WARNING "%s: device %s already bound\n", __func__, kobject_name(&dev->kobj)); return; } pr_debug("driver: '%s': %s: bound to device '%s'\n", dev_name(dev), __func__, dev->driver->name); klist_add_tail(&dev->p->knode_driver, &dev->driver->p->klist_devices); if (dev->bus) blocking_notifier_call_chain(&dev->bus->p->bus_notifier, BUS_NOTIFY_BOUND_DRIVER, dev); }
此把设备加入了驱动的的设备链表。
中间还落下了一部分 就是 real_probe(dev, drv) 函数 的
if (dev->bus->probe) { ret = dev->bus->probe(dev); if (ret) goto probe_failed; } else if (drv->probe) { ret = drv->probe(dev); if (ret) goto probe_failed; }
此处就是调用了
static struct platform_driver s3c24xx_i2c_driver = { .probe = s3c24xx_i2c_probe, .remove = s3c24xx_i2c_remove, .id_table = s3c24xx_driver_ids, .driver = { .owner = THIS_MODULE, .name = "s3c-i2c", .pm = S3C24XX_DEV_PM_OPS, }, };
的 s3c_i2c_probe 函数。 此处要明确下,处传给s3c_i2c_probe 的参数是 我们注册的i2c 平台设备 s3c_device_i2c0
/* s3c24xx_i2c_probe * * called by the bus driver when a suitable device is found */ static int s3c24xx_i2c_probe(struct platform_device *pdev) { struct s3c24xx_i2c *i2c; //s3c24xx_i2c 对i2c控制器进行了封装 struct s3c2410_platform_i2c *pdata; struct resource *res; int ret; pdata = pdev->dev.platform_data; if (!pdata) { dev_err(&pdev->dev, "no platform data\n"); return -EINVAL; } i2c = kzalloc(sizeof(struct s3c24xx_i2c), GFP_KERNEL); //为i2c控制器申请空间 if (!i2c) { dev_err(&pdev->dev, "no memory for state\n"); return -ENOMEM; } strlcpy(i2c->adap.name, "s3c2410-i2c", sizeof(i2c->adap.name)); i2c->adap.owner = THIS_MODULE; i2c->adap.algo = &s3c24xx_i2c_algorithm; i2c->adap.retries = 2; i2c->adap.class = I2C_CLASS_HWMON | I2C_CLASS_SPD; i2c->tx_setup = 50; spin_lock_init(&i2c->lock); init_waitqueue_head(&i2c->wait); /* find the clock and enable it */ i2c->dev = &pdev->dev; i2c->clk = clk_get(&pdev->dev, "i2c"); if (IS_ERR(i2c->clk)) { dev_err(&pdev->dev, "cannot get clock\n"); ret = -ENOENT; goto err_noclk; } dev_dbg(&pdev->dev, "clock source %p\n", i2c->clk); clk_enable(i2c->clk); /* map the registers */ res = platform_get_resource(pdev, IORESOURCE_MEM, 0); if (res == NULL) { dev_err(&pdev->dev, "cannot find IO resource\n"); ret = -ENOENT; goto err_clk; } i2c->ioarea = request_mem_region(res->start, resource_size(res), pdev->name); if (i2c->ioarea == NULL) { dev_err(&pdev->dev, "cannot request IO\n"); ret = -ENXIO; goto err_clk; } i2c->regs = ioremap(res->start, resource_size(res)); if (i2c->regs == NULL) { dev_err(&pdev->dev, "cannot map IO\n"); ret = -ENXIO; goto err_ioarea; } dev_dbg(&pdev->dev, "registers %p (%p, %p)\n", i2c->regs, i2c->ioarea, res); /* setup info block for the i2c core */ i2c->adap.algo_data = i2c; i2c->adap.dev.parent = &pdev->dev; /* initialise the i2c controller */ ret = s3c24xx_i2c_init(i2c); if (ret != 0) goto err_iomap; /* find the IRQ for this unit (note, this relies on the init call to * ensure no current IRQs pending */ i2c->irq = ret = platform_get_irq(pdev, 0); if (ret <= 0) { dev_err(&pdev->dev, "cannot find IRQ\n"); goto err_iomap; } ret = request_irq(i2c->irq, s3c24xx_i2c_irq, IRQF_DISABLED, dev_name(&pdev->dev), i2c); if (ret != 0) { dev_err(&pdev->dev, "cannot claim IRQ %d\n", i2c->irq); goto err_iomap; } ret = s3c24xx_i2c_register_cpufreq(i2c); if (ret < 0) { dev_err(&pdev->dev, "failed to register cpufreq notifier\n"); goto err_irq; } /* Note, previous versions of the driver used i2c_add_adapter() * to add the bus at any number. We now pass the bus number via * the platform data, so if unset it will now default to always * being bus 0. */ i2c->adap.nr = pdata->bus_num; ret = i2c_add_numbered_adapter(&i2c->adap); if (ret < 0) { dev_err(&pdev->dev, "failed to add bus to i2c core\n"); goto err_cpufreq; } platform_set_drvdata(pdev, i2c); dev_info(&pdev->dev, "%s: S3C I2C adapter\n", dev_name(&i2c->adap.dev)); clk_disable(i2c->clk); return 0; err_cpufreq: s3c24xx_i2c_deregister_cpufreq(i2c); err_irq: free_irq(i2c->irq, i2c); err_iomap: iounmap(i2c->regs); err_ioarea: release_resource(i2c->ioarea); kfree(i2c->ioarea); err_clk: clk_disable(i2c->clk); clk_put(i2c->clk); err_noclk: kfree(i2c); return ret; }
此函数明天继续分析