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一. 简介

本文来学习 Linux内核中的 platform总线。

二.  Linux下platform总线

1. platform总线的结构体

struct bus_type {const char		*name;const char		*dev_name;struct device		*dev_root;struct device_attribute	*dev_attrs;	/* use dev_groups instead */const struct attribute_group **bus_groups;const struct attribute_group **dev_groups;const struct attribute_group **drv_groups;int (*match)(struct device *dev, struct device_driver *drv);int (*uevent)(struct device *dev, struct kobj_uevent_env *env);int (*probe)(struct device *dev);int (*remove)(struct device *dev);void (*shutdown)(struct device *dev);int (*online)(struct device *dev);int (*offline)(struct device *dev);int (*suspend)(struct device *dev, pm_message_t state);int (*resume)(struct device *dev);const struct dev_pm_ops *pm;const struct iommu_ops *iommu_ops;struct subsys_private *p;struct lock_class_key lock_key;
};

第 10 行，match 函数，此函数就是完成设备和驱动之间匹配的。总线就是使用 match 函数来根据注册的设备来查找对应的驱动，或者根据注册的驱动来查找相应的设备，因此，每一条总线都必须实现此函数。

match 函数有 两个参数：dev 和 drv，这两个参数分别为 device 和 device_driver 类型，也就是设备和驱动。

struct bus_type platform_bus_type = {.name		= "platform",.dev_groups	= platform_dev_groups,.match		= platform_match,.uevent		= platform_uevent,.pm		= &platform_dev_pm_ops,
};

2. 驱动与设备是如何匹配的？

static int platform_match(struct device *dev, struct device_driver *drv)
{struct platform_device *pdev = to_platform_device(dev);struct platform_driver *pdrv = to_platform_driver(drv);/* When driver_override is set, only bind to the matching driver */if (pdev->driver_override)return !strcmp(pdev->driver_override, drv->name);/* Attempt an OF style match first */if (of_driver_match_device(dev, drv))return 1;/* Then try ACPI style match */if (acpi_driver_match_device(dev, drv))return 1;/* Then try to match against the id table */if (pdrv->id_table)return platform_match_id(pdrv->id_table, pdev) != NULL;/* fall-back to driver name match */return (strcmp(pdev->name, drv->name) == 0);
}