Reviewing the bus device driver model, I’ve made a few notes for reference, experts can skip this.
1. A significant part of the driver framework in the Linux system revolves around the bus device driver model.
2. Involves three important structures:
struct bus_type: Bus
struct device: Device
struct device_driver: Driver
3. Core code analysis of the structures (Kernel 2.6.38)
struct bus_type
{
const char *name; // Bus name
struct bus_attribute *bus_attrs; // Bus attribute files, displayed in /sys/xxx
struct device_attribute *dev_attrs; // Device attribute files
struct driver_attribute *drv_attrs; // Driver attribute files
int (*match)(struct device*dev, struct device_driver *drv);// Function to check if driver matches device
struct subsys_private *p;
};
Among them, struct subsys_private contains a device linked list (struct klist klist_devices) and a driver linked list (struct klist klist_drivers)
struct device
{
struct kobject kobj;
const char // Device name
struct bus_type *bus; // Which bus this device is attached to
struct device_driver*driver; // Corresponding driver for this device
void *platform_data; // Platform-specific data, typically filled when porting the kernel (e.g., supporting mini2440 NAND flash, dm9000, etc.)
dev_t devt; // Device number
};
Any driver code built on the platform bus device driver model (such as platform drivers, PCI drivers, USB drivers, I2C drivers, SPI drivers, etc.) includes a struct device structure, and when these drivers register various devices with the kernel, they ultimately call:
int device_register(struct device *dev)
{
device_initialize(dev); // Perform various initializations
// Attach the device to the corresponding bus, mainly adding the device to the bus_type’s klist_devices linked list
return device_add(dev);
}
struct device_driver {
const char *name;// Driver name
struct bus_type *bus;// The bus to which this driver belongs
int (*probe) (struct device *dev);// Points to the device probe function
int (*remove) (struct device*dev);// Points to the device removal function
struct driver_private *p;
};
Similarly, any driver code built on the platform bus device driver model (such as platform drivers, PCI drivers, USB drivers, I2C drivers, SPI drivers, etc.) includes a struct device_driver structure, and when these drivers register various drivers with the kernel, they ultimately call:
int driver_register(struct device_driver *drv)
{
// Bind the driver to the corresponding bus, mainly adding the driver to the bus_type’s klist_drivers linked list
ret = bus_add_driver(drv);
}
Whether calling driver_register() to register a driver or using device_register to register a device, the kernel will invoke the bus’s match function to check if there is a suitable device_driver for the device or a suitable device for the device_driver. If the match is successful, the device_driver’s probe function will be called for further probing.
Thus, we can view drivers from a new perspective.
For more specific content on how to detect and set up probes, please refer to the related videos of Wei Dongshan’s second series on driver compilation.
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