Ashmem是Android提供的共享內存的IPC機制，通過驅動程序 提供共享內存實現
驅動提供的方法
static const struct file_operations ashmem_fops = {
.owner = THIS_MODULE,
.open = ashmem_open,
.release = ashmem_release,
.read = ashmem_read,
.llseek = ashmem_llseek,
.mmap = ashmem_mmap,
.unlocked_ioctl = ashmem_ioctl,
.compat_ioctl = ashmem_ioctl,
};
驅動設備struct抽象
static struct miscdevice ashmem_misc = {
.minor = MISC_DYNAMIC_MINOR,
.name = "ashmem",
.fops = &ashmem_fops,
};
驅動init、release
static int __init ashmem_init(void)
{
int ret;
ashmem_area_cachep = kmem_cache_create("ashmem_area_cache",
sizeof(struct ashmem_area),
0, 0, NULL);
if (unlikely(!ashmem_area_cachep)) {
printk(KERN_ERR "ashmem: failed to create slab cache\n");
return -ENOMEM;
}
ashmem_range_cachep = kmem_cache_create("ashmem_range_cache",
sizeof(struct ashmem_range),
0, 0, NULL);
if (unlikely(!ashmem_range_cachep)) {
printk(KERN_ERR "ashmem: failed to create slab cache\n");
return -ENOMEM;
}
ret = misc_register(&ashmem_misc);
if (unlikely(ret)) {
printk(KERN_ERR "ashmem: failed to register misc device!\n");
return ret;
}
register_shrinker(&ashmem_shrinker);
printk(KERN_INFO "ashmem: initialized\n");
return 0;
}
static void __exit ashmem_exit(void)
{
int ret;
unregister_shrinker(&ashmem_shrinker);
ret = misc_deregister(&ashmem_misc);
if (unlikely(ret))
printk(KERN_ERR "ashmem: failed to unregister misc device!\n");
kmem_cache_destroy(ashmem_range_cachep);
kmem_cache_destroy(ashmem_area_cachep);
printk(KERN_INFO "ashmem: unloaded\n");
}
module_init(ashmem_init);
module_exit(ashmem_exit);
MODULE_LICENSE("GPL");