The Linux Driver Model Overview
The Linux driver model forms the backbone of how the Linux kernel manages hardware devices and their drivers. This model provides a structured way for the kernel to keep track of all devices, drivers, and the buses they use to communicate. By organizing these components systematically, the Linux driver model ensures that devices are matched with the correct drivers, and that the kernel can expose relevant information and controls to user space. This architecture is crucial for scalability, maintainability, and the ability to support a wide variety of hardware platforms.
linux_driver_model_example.c
1234567891011121314151617181920212223242526272829303132333435363738394041424344#include <linux/module.h> #include <linux/device.h> #include <linux/init.h> #include <linux/kernel.h> static struct device_driver example_driver = { .name = "example_driver", .bus = &platform_bus_type, // Using platform bus for demonstration }; static struct device example_device = { .init_name = "example_device", .bus = &platform_bus_type, }; static int __init example_init(void) { int ret; // Register the driver ret = driver_register(&example_driver); if (ret) return ret; // Register the device ret = device_register(&example_device); if (ret) driver_unregister(&example_driver); return ret; } static void __exit example_exit(void) { device_unregister(&example_device); driver_unregister(&example_driver); } module_init(example_init); module_exit(example_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Linux Driver Model Example"); MODULE_DESCRIPTION("Basic device and driver registration example");
Within the Linux driver model, three major components interact: devices, drivers, and buses. A device represents a physical or virtual piece of hardware, while a driver is the software that controls and communicates with that device. The bus is the communication channel that connects devices to the system and allows the kernel to discover and manage them. In the registration code above, you see how a device and a driver are both registered with the kernel, each associated with the same bus type. This association enables the kernel to match devices with suitable drivers automatically, ensuring that hardware is managed correctly and efficiently.
linux_sysfs_attribute_example.c
1234567891011121314151617181920212223242526272829303132333435#include <linux/module.h> #include <linux/device.h> #include <linux/kernel.h> static ssize_t show_example(struct device *dev, struct device_attribute *attr, char *buf) { return sprintf(buf, "Hello from sysfs!\n"); } static DEVICE_ATTR(example, S_IRUGO, show_example, NULL); static struct device *example_device; static int __init sysfs_example_init(void) { example_device = root_device_register("sysfs_example_device"); if (IS_ERR(example_device)) return PTR_ERR(example_device); // Create a sysfs attribute for this device return device_create_file(example_device, &dev_attr_example); } static void __exit sysfs_example_exit(void) { device_remove_file(example_device, &dev_attr_example); root_device_unregister(example_device); } module_init(sysfs_example_init); module_exit(sysfs_example_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Sysfs Attribute Example"); MODULE_DESCRIPTION("Simple sysfs attribute creation for a device");
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The Linux driver model forms the backbone of how the Linux kernel manages hardware devices and their drivers. This model provides a structured way for the kernel to keep track of all devices, drivers, and the buses they use to communicate. By organizing these components systematically, the Linux driver model ensures that devices are matched with the correct drivers, and that the kernel can expose relevant information and controls to user space. This architecture is crucial for scalability, maintainability, and the ability to support a wide variety of hardware platforms.
linux_driver_model_example.c
1234567891011121314151617181920212223242526272829303132333435363738394041424344#include <linux/module.h> #include <linux/device.h> #include <linux/init.h> #include <linux/kernel.h> static struct device_driver example_driver = { .name = "example_driver", .bus = &platform_bus_type, // Using platform bus for demonstration }; static struct device example_device = { .init_name = "example_device", .bus = &platform_bus_type, }; static int __init example_init(void) { int ret; // Register the driver ret = driver_register(&example_driver); if (ret) return ret; // Register the device ret = device_register(&example_device); if (ret) driver_unregister(&example_driver); return ret; } static void __exit example_exit(void) { device_unregister(&example_device); driver_unregister(&example_driver); } module_init(example_init); module_exit(example_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Linux Driver Model Example"); MODULE_DESCRIPTION("Basic device and driver registration example");
Within the Linux driver model, three major components interact: devices, drivers, and buses. A device represents a physical or virtual piece of hardware, while a driver is the software that controls and communicates with that device. The bus is the communication channel that connects devices to the system and allows the kernel to discover and manage them. In the registration code above, you see how a device and a driver are both registered with the kernel, each associated with the same bus type. This association enables the kernel to match devices with suitable drivers automatically, ensuring that hardware is managed correctly and efficiently.
linux_sysfs_attribute_example.c
1234567891011121314151617181920212223242526272829303132333435#include <linux/module.h> #include <linux/device.h> #include <linux/kernel.h> static ssize_t show_example(struct device *dev, struct device_attribute *attr, char *buf) { return sprintf(buf, "Hello from sysfs!\n"); } static DEVICE_ATTR(example, S_IRUGO, show_example, NULL); static struct device *example_device; static int __init sysfs_example_init(void) { example_device = root_device_register("sysfs_example_device"); if (IS_ERR(example_device)) return PTR_ERR(example_device); // Create a sysfs attribute for this device return device_create_file(example_device, &dev_attr_example); } static void __exit sysfs_example_exit(void) { device_remove_file(example_device, &dev_attr_example); root_device_unregister(example_device); } module_init(sysfs_example_init); module_exit(sysfs_example_exit); MODULE_LICENSE("GPL"); MODULE_AUTHOR("Sysfs Attribute Example"); MODULE_DESCRIPTION("Simple sysfs attribute creation for a device");
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