1 Android 驱动代码编译

参考https://www.sharetechnote.com/html/Linux_DeviceDriver_Programing.html#Device_Driver_HelloWorld编译ko文件调试驱动代码，将ko文件push到手机上验证

相关C文件testdriver.c

#include <linux/init.h>
#include <linux/module.h>
static int __init testdriver_init(void)
{printk("Test Driver Initialized\n");return 0;
}
static void __exit testdriver_exit(void)
{printk("Test Driver Being Removed\n");
}
module_init(testdriver_init);
module_exit(testdriver_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("ShareTechnote");
MODULE_DESCRIPTION("Test Driver : The Simplest Driver");
MODULE_VERSION("1.0.0");

相关Make file文件如下

obj-m += testdriver.o 
KDIR  := /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd) 
default:
$(MAKE) -C $(KDIR) M=$(PWD) modules

Make编译

编译成功后push到手机上data/data目录，安装后报错

insmod: failed to load testdriver.ko: Exec format error

原因1：内核版本不一致

手机内核版本，使用uname -r

电脑内核版本为：5.4.0-137-generic

原因2：网上搜索后需要使用ARM交叉编译

Make file参考网络建议修改Makefile，相关Make file文件如下

obj-m += testdriver.oKDIR  := ${OUT}/obj/KERNEL_OBJ/$(info kdir is $(KDIR))PWD := $(shell pwd)$(info pwd is $(PWD))default:$(MAKE) CROSS_COMPILE=aarch64-linux-gnu- LLVM=1 LLVM_IAS=1  ARCH=arm64 -C $(KDIR) M=$(PWD) modules

编译报错，尝试各种方式无法解决该问题

解决方案：搜索相关MTK基线上相关代码，在vendor\mediatek\kernel_modules上有MTK加的相关KO文件的编译，添加Android.mk，修改Makefile如下

Android.mk文件

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

$(info zmao android mk start)

LOCAL_MODULE := testdriver.ko

LOCAL_PROPRIETARY_MODULE := true

LOCAL_MODULE_OWNER := mtk

LOCAL_SRC_FILES := \

testdriver.c \

Makefile

ifeq ($(TARGET_OUT_VENDOR),)

LOCAL_MODULE_PATH := $(ALPS_OUT)/vendor/lib/modules

else

LOCAL_MODULE_PATH := $(TARGET_OUT_VENDOR)/lib/modules

endif

$(info kernel mode is $(MTK_KERNEL_MODULE))

include $(MTK_KERNEL_MODULE)

Makefile文件

$(warning zmao start complie)

$(warning ########################### is $(srctree))

ccflags-y += -Wno-unused-variable

ldflags-y += -s

obj-m += testdriver.o

$(warning zmao success !!!!!!!)

成功编译出ko文件，push到手机上测试，成功安装驱动程序

2、调试驱动程序时出现 No such device or address Error

网上搜了很多，最后发现open函数没有执行，需要添加如下代码

    printk("zmao init start \n");

    cdev_init(&_cdev,&testdriver_fops);

    _cdev.owner = THIS_MODULE;

    _cdev.ops = &testdriver_fops;//Create Dev and file_operations Connected

    cdev_add(&_cdev,first,1);

    printk("zmao init end %d \n");

static int __init testdriver_init(void){printk("zmao Test Driver Initialized\n");if (alloc_chrdev_region(&first, 0, 3, "TestDriver") < 0){return -1;}printk("zmao <Major, Minor>: <%d, %d>\n", MAJOR(first), MINOR(first));if ((cl = class_create(THIS_MODULE, "chardrv")) == NULL){printk(KERN_INFO "class_create() failed");unregister_chrdev_region(first, 1);return -1;}if (device_create(cl, NULL, first, NULL, "testdriver") == NULL){printk("zmao device_create() failed");class_destroy(cl);unregister_chrdev_region(first, 1);return -1;}printk("zmao init start \n");cdev_init(&_cdev,&testdriver_fops);_cdev.owner = THIS_MODULE;_cdev.ops = &testdriver_fops;//Create Dev and file_operations Connectedcdev_add(&_cdev,first,1);printk("zmao init end %d \n");return 0;}

3、添加C进程访问内核驱动 

Android.mk文件

LOCAL_PATH := $(call my-dir)
$(info start client compile ++++)
include $(CLEAR_VARS)  
LOCAL_MODULE_TAGS := optional  
LOCAL_SRC_FILES := rwtest.c   
LOCAL_MODULE := rwtest
LOCAL_MODULE_CLASS := EXECUTABLES
$(info start client compile ----)
include $(BUILD_EXECUTABLE)

rwtest.c文件 

#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
int main()
{int fd;int ret = 0;char buff[100];fd = open("/dev/testdriver",O_RDWR);if(fd < 0) {printf("/dev/testdriver open failed (ret = %d)\n",fd);return 1;};ret = read(fd,buff,10);printf("%s\n",buff);ret = write(fd,"Hello",6);close(fd);return 1;
}