Add hlist usage example

Change-Id: Ibe51396e3a0cb24189cfa760c783a97258c521db

Author: 54shady

debug/hlist/Makefile

@@ -0,0 +1,37 @@
+# Makefile
+# Comment/uncomment the following line to disable/enable debugging
+# DEBUG = y
+
+# Usage
+# make CROSS_COMPILE=<cross_compiler_prefix> KERNEL_DIR=<your_kernel_dir> KERNEL_BUID_OUTPUT=<kernel_buid_output>
+#
+# make CROSS_COMPILE=/home/zeroway/rk3399/tool/gcc-linaro-4.9.4-2017.01-i686_aarch64-linux-gnu/bin/aarch64-linux-gnu- KERNEL_DIR=/home/zeroway/rk3399/src/firefly/kernel KERNEL_BUID_OUTPUT=/home/zeroway/rk3399/src/firefly/out/target/product/rk3399_firefly_box/obj/KERNEL
+
+# Add your debugging flag (or not) to CFLAGS
+ifeq ($(DEBUG),y)
+DEBFLAGS = -O -g -DSCULL_DEBUG # "-O" is needed to expand inlines
+else
+DEBFLAGS = -O2
+endif
+
+obj-m := demo.o
+
+KERNEL_DIR ?= /lib/modules/`uname -r`/build
+KERNEL_BUID_OUTPUT ?=$(KERNEL_DIR)
+CC = $(CROSS_COMPILE)gcc
+LD = $(CROSS_COMPILE)ld
+PWD := $(shell pwd)
+ARCH := x86_64
+
+modules:
+	$(MAKE) -C $(KERNEL_DIR) ARCH=$(ARCH) M=$(PWD) O=$(KERNEL_DIR) modules
+
+clean:
+	rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions modules.order Module.symvers
+
+depend .depend dep:
+	$(CC) $(CFLAGS) -M *.c > .depend
+
+ifeq (.depend,$(wildcard .depend))
+include .depend
+endif

debug/hlist/demo.c

@@ -0,0 +1,71 @@
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+/* refercence with kernel module zd1201 */
+/* https://zhuanlan.zhihu.com/p/82375193 */
+struct AAAAA {
+	/* hash table implement in list address */
+	struct hlist_head nodelist;
+};
+
+struct AAAAA_node {
+	struct hlist_node fnode;
+	char name[20];
+};
+
+struct AAAAA *module5a;
+static int hlist_test_init(void)
+{
+	struct AAAAA_node *node1;
+	struct AAAAA_node *node2;
+	struct AAAAA_node *pos;
+
+	/* another hlist_node to use as temporary storage */
+	struct hlist_node *tmp_node;
+
+	module5a = kmalloc(sizeof(struct AAAAA), GFP_ATOMIC);
+	if (!module5a)
+		return -1;
+
+	node1 = kmalloc(sizeof(*node1), GFP_ATOMIC);
+	if (!node1)
+		return -1;
+	strcpy(node1->name, "Node1");
+
+	node2 = kmalloc(sizeof(*node2), GFP_ATOMIC);
+	if (!node2)
+		return -1;
+	strcpy(node2->name, "Node2");
+
+	/* init hash table */
+	INIT_HLIST_HEAD(&module5a->nodelist);
+
+	/* add node to hash table */
+	hlist_add_head(&node1->fnode, &module5a->nodelist);
+	hlist_add_head(&node2->fnode, &module5a->nodelist);
+
+	hlist_for_each_entry_safe(pos, tmp_node, &module5a->nodelist, fnode) {
+		printk(KERN_ALERT"Iter node : %s\n", pos->name);
+	}
+
+	return 0;
+}
+
+static void hlist_test_exit(void)
+{
+	struct AAAAA_node *pos;
+	struct hlist_node *tmp_node;
+
+	hlist_for_each_entry_safe(pos, tmp_node, &module5a->nodelist, fnode) {
+		printk(KERN_ALERT"Delete node : %s\n", pos->name);
+		hlist_del_init(&pos->fnode);
+		kfree(pos);
+	}
+	kfree(module5a);
+}
+
+MODULE_LICENSE("Dual BSD/GPL");
+module_init(hlist_test_init);
+module_exit(hlist_test_exit);