Shulou(Shulou.com)06/01 Report--

This article to share with you is about how to initialize APM in Linux, Xiaobian think it is very practical, so share it with you to learn, I hope you can gain something after reading this article, not much to say, follow Xiaobian to see it.

The misc device's primary device number is 10, and Linux APM_bios as a misc device has a secondary device number of 134. Linux 2.6.30.10 kernel/drivers/char/apm-emulation.c provides the Linux APM_bios driver model, that is, the system to enter sleep entry function, earlier versions of the interface file: arch/arm/kernel/apm.c

In Linux APM-emulation.c:

/* * The apm_bios device is one of the misc char devices. * This is its minor number. */ #define Linux APM_MINOR_DEV 134

The Linux APM_bios device communicates with user space via the ioctl system call, i.e. when a user process issues a suspend command via ioctl, it passes it to the kernel, putting the system into the suspend state.

1, Initialize

static int __init apm_init(void) { int ret; if (apm_disabled) { printk(KERN_NOTICE "apm: disabled on user request.\ n"); return -ENODEV; }

//Create a thread to process the event queue, the worker function is kapmd

kapmd_tsk = kthread_create(kapmd, NULL, "kapmd"); if (IS_ERR(kapmd_tsk)) { ret = PTR_ERR(kapmd_tsk); kapmd_tsk = NULL; goto out; } wake_up_process(kapmd_tsk);

//Output Linux APM information to user space via proc

#ifdef CONFIG_PROC_FS proc_create("apm", 0, NULL, &apm_proc_fops); #endif

//Register misc device

ret = misc_register (&apm_device); if (ret) goto out_stop; ret = register_pm_notifier (&apm_notif_block); if (ret) goto out_unregister; return 0; out_unregister: misc_deregister (&apm_device); out_stop: remove_proc_entry ("apm", NULL); kthread_stop(kapmd_tsk); out: return ret; } The above is how to initialize APM in Linux. Xiaobian believes that some knowledge points may be seen or used in our daily work. I hope you can learn more from this article. For more details, please follow the industry information channel.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.