Linux驱动杂项

1、Linux驱动学习杂项：fschar_dev.c字符驱动为一个字符设备注册主设备号，Major：主设备号，0-255/* * register_chrdev() - Register a major number for character devices. * major: major device number or 0 for dynamic allocation * name: name of this range of devices * fops: associated with this devices * * If major = 0 this functions will d

2、ynamically allocate a major and return * its number. * * If major > 0 this function will attempt to reserve a device with the given * major number and will return zero on success. * * Returns a -ve errno on failure. * * The name of this device has nothing to do with the name of the device in * /d

3、ev. It only helps to keep track of the different owners of devices. If * your module name has only one type of devices it's ok to use e.g. the name * of the module here. * * This function registers a range of 256 minor numbers. The first minor number * is 0. */int register_chrdev(unsigned int ma

4、jor, const char *name, const struct *fops)struct char_device_struct *cd;struct cdev *cdev;char *s;int err = -ENOMEM;cd = _register_chrdev_region(major, 0, 256, name);if (IS_ERR(cd)return PTR_ERR(cd);cdev = cdev_alloc();if (!cdev)goto out2;cdev->owner = fops->owner;cdev->ops = fops;kobject_s

5、et_name(&cdev->kobj, "%s", name);for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/')*s = '!'err = cdev_add(cdev, MKDEV(cd->major, 0), 256);if (err)goto out;cd->cdev = cdev;return major ? 0 : cd->major;out:kobject_put(&cde

6、v->kobj);out2:kfree(_unregister_chrdev_region(cd->major, 0, 256);return err;MKDEV构造设备号：includelinuxkdev_t.h#define MINORBITS20#define MKDEV(ma,mi)(ma) << MINORBITS) | (mi)MKDEV构造设备号，高12位为主设备号major，低20位为次设备号minor在这里设置了一些主设备号：includelinuxmajor.h#define UNNAMED_MAJOR0#define MEM_MAJOR1#defi

7、ne RAMDISK_MAJOR1#define FLOPPY_MAJOR2#define PTY_MASTER_MAJOR2#define IDE0_MAJOR3#define HD_MAJORIDE0_MAJOR#define PTY_SLAVE_MAJOR3#define TTY_MAJOR4#define TTYAUX_MAJOR5#define LP_MAJOR6#define VCS_MAJOR7#define LOOP_MAJOR7#define SCSI_DISK0_MAJOR8#define SCSI_TAPE_MAJOR9#define MD_MAJOR9#define M

8、ISC_MAJOR10#define SCSI_CDROM_MAJOR11#define MUX_MAJOR11/* PA-RISC only */#define XT_DISK_MAJOR13#define INPUT_MAJOR13#define SOUND_MAJOR14Misc.c是杂项设备，是char设备的一种，只不过是主设备号major是10的char设备。includelinuxmiscdevice.h这是头文件，要使用MISC设备，包含这个头文件，函数有注册与否。#define PSMOUSE_MINOR1#define MS_BUSMOUSE_MINOR2#define PC

9、110PAD_MINOR9#define WATCHDOG_MINOR130/* Watchdog timer */#define TEMP_MINOR131/* Temperature Sensor */#define RTC_MINOR135#define I2O_MINOR166#define MICROCODE_MINOR184#define FUSE_MINOR229#define KVM_MINOR232#define MISC_DYNAMIC_MINOR255struct device;struct miscdevice int minor;const char *name;co

10、nst struct *fops;struct list_head list;struct device *parent;struct device *this_device;extern int misc_register(struct miscdevice * misc);extern int misc_deregister(struct miscdevice *misc);可以看出许多设备都是MISC设备，主要是次设备号不同，像TEMP，I2C，RTC等。driverscharMisc.c/* *misc_register-register a miscellaneous device

11、*misc: device structure * *Register a miscellaneous device with the kernel. If the minor *number is set to %MISC_DYNAMIC_MINOR a minor number is assigned *and placed in the minor field of the structure. For other cases *the minor number requested is used. * *The structure passed is linked into the k

12、ernel and may not be *destroyed until it has been unregistered. * *A zero is returned on success and a negative errno code for *failure. */ int misc_register(struct miscdevice * misc)struct miscdevice *c;dev_t dev;int err = 0;INIT_LIST_HEAD(&misc->list);mutex_lock(&misc_mtx);list_for_each

13、_entry(c, &misc_list, list) if (c->minor = misc->minor) mutex_unlock(&misc_mtx);return -EBUSY;if (misc->minor = MISC_DYNAMIC_MINOR) int i = DYNAMIC_MINORS;while (-i >= 0)if ( (misc_minorsi>>3 & (1 << (i&7) = 0)break;if (i<0) mutex_unlock(&misc_mtx);retu

14、rn -EBUSY;misc->minor = i;if (misc->minor < DYNAMIC_MINORS)misc_minorsmisc->minor >> 3 |= 1 << (misc->minor & 7);dev = MKDEV(MISC_MAJOR, misc->minor);misc->this_device = device_create(misc_class, misc->parent, dev, NULL, "%s", misc->name);if (IS_ERR(misc->this_device) err = PTR_ERR(misc-