开发Android硬件驱动程序程序和C验证程序

开发坏境

本地在在6.x的环境上调试

Android版本号：mtk_6737_6.x
Linux内核 版本号：Linux version 3.18.19+ ，arm64 //cat /proc/version

开发Androd硬件驱动

实现内核驱动程序模块

驱动文件包括三个文件：
Kconfig,Makefile,hello.c

• hello.c

#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <linux/proc_fs.h>
#include <linux/device.h>
struct hello_cdev{
    char val;
    struct cdev cv;
};
dev_t devNo1;
struct hello_cdev *hello_c;

int hello_open (struct inode *node, struct file *filp){
    //获取到当前自定义结构体变量，保存至file中，以便其他函数方便访问
    struct hello_cdev *n_cdev = container_of(node->i_cdev,struct hello_cdev,cv);
    filp->private_data = n_cdev;
    return 0;
}

int hello_release (struct inode *node, struct file *filp){
    filp->private_data = NULL;
    return 0;
}

ssize_t hello_read (struct file *filp, char __user *buf, size_t len, loff_t *pos){
    struct hello_cdev *n_cdev = (struct hello_cdev *)filp->private_data;
    int err;
    printk("hello read %c  count : %d",n_cdev->val, sizeof(n_cdev->val));
    if(copy_to_user(buf,&n_cdev->val, sizeof(n_cdev->val))){
        err = -EFAULT;
        return err;
    }
    return sizeof(n_cdev->val);

}

ssize_t hello_write (struct file *filp, const char __user *buf, size_t len, loff_t *pos){
    struct hello_cdev *n_cdev = (struct hello_cdev *)filp->private_data;
    int err;
    printk("hello write %s  count : %d",(buf),len);
    if(copy_from_user(&n_cdev->val,buf,len)){
        err = -EFAULT;
        return err;
    }
    return sizeof(n_cdev->val);
}

struct file_operations hello_op = {
    .owner = THIS_MODULE,
    .open  = hello_open,
    .release = hello_release,
    .write = hello_write,
    .read = hello_read
};




static int hello_init(void){
    //申请设备号，自动分配 fs.h
    int err = alloc_chrdev_region(&devNo1,0,1,"hello");
    if(err){
        printk("获取设备号失败～ %d",err);
        return err;
    }
    //申请自定义结构体内存 slab.h
    hello_c = kmalloc(sizeof(struct hello_cdev),GFP_KERNEL);
    //初始化 字符设备
    cdev_init(&hello_c->cv,&hello_op);
    //添加字符设备
    err = cdev_add(&hello_c->cv,devNo1,1);
    if(err){
        printk("添加设备失败～ %d",err);
        return err;
    }

    hello_c->val = '1';
    //在/dev中创建节点
    struct class * cls = class_create(THIS_MODULE,"hello");
    device_create(cls,NULL,devNo1,NULL,"hello");

    return 0;
}

static void hello_exit(void){
    //释放设备号
    unregister_chrdev_region(devNo1,1);
    //释放自定义结构体的内存
    kfree(hello_c);
    //移除字符设备
    cdev_del(&hello_c->cv);
}


module_init(hello_init);
module_exit(hello_exit);

• Kconfig

config HELLO
    tristate 'HELLO Driver'
    default n

• Makefile

obj-y  += hello.o

把以上三个文件，放到源码的kernel的驱动目录

//kernel目录选择当前源码中最新版本目录
android\xxx\kernel-3.18\drivers\hello

修改内核drivers目录的Kconfig和Makefile文件

关联我们创建的模块
Kconfig

diff --git a/kernel-4.9/drivers/Kconfig b/kernel-3.18/drivers/Kconfig
index c38428c..5626ff9 100755
--- a/kernel-3.18/drivers/Kconfig
+++ b/kernel-3.18/drivers/Kconfig
@@ -1,5 +1,9 @@
 menu "Device Drivers"
 
+source "drivers/hello/Kconfig"

 source "drivers/amba/Kconfig"
 
 source "drivers/base/Kconfig"

Makefile

diff --git a/kernel-3.18/drivers/Makefile b/kernel-3.18/drivers/Makefile
index 6750823..588796a 100755
--- a/kernel-4.9/drivers/Makefile
+++ b/kernel-4.9/drivers/Makefile
@@ -179,3 +179,5 @@ obj-$(CONFIG_NVMEM)         += nvmem/
 obj-$(CONFIG_FPGA)             += fpga/
 obj-$(CONFIG_TEE)              += tee/
 obj-$(CONFIG_TRUSTY)   += trusty/
+obj-y        += hello/

必须使用obj-y ，这样才会把生成的hello.o文件编译进内核,如果你使用obj-$(CONFIG_HELLO),则还需要参考配置默认打开驱动模块去配置CONFIG_HELLO变量

CONFIG_HELLO属性默认为not set，也就是“n”

关联之后，我们的模块已经添加到kernel驱动中去了，但此时模块是默认关闭的，因此我们还需要在源码中默认打开改功能

配置默认打开驱动模块

此步骤，只有在drivers/Makefile 中配置obj-$(CONFIG_HELLO) +=hello而非obj-y方式下，才需要配置属性，如果你使用的是obj-y ，此章节略过

确认需要修改的defconfig文件

驱动模块默认是关闭的，需要修改kernel-3.18/arch/arm64/configs的deconfig文件，默认打开改功能
该目录下有多个defconfig文件，怎么确认需要修改哪个文件呢？

lunch工程后，查看对应的TARGET_PRODUCT

#source build/envsetup.sh 

#full_yk658_37m_lwtg_35g-userdebug
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=6.0
TARGET_PRODUCT=full_yk658_37m_lwtg_35g
TARGET_BUILD_VARIANT=userdebug
TARGET_BUILD_TYPE=release
TARGET_BUILD_APPS=
TARGET_ARCH=arm
TARGET_ARCH_VARIANT=armv7-a-neon
TARGET_CPU_VARIANT=cortex-a53
TARGET_2ND_ARCH=
TARGET_2ND_ARCH_VARIANT=
TARGET_2ND_CPU_VARIANT=cortex-a53
HOST_ARCH=x86_64
HOST_OS=linux
HOST_OS_EXTRA=Linux-3.19.0-25-generic-x86_64-with-Ubuntu-14.04-trusty
HOST_BUILD_TYPE=release
BUILD_ID=MRA58K
OUT_DIR=out

可以看到TARGET_PRODUCT=full_yk658_37m_lwtg_35g，然后去TARGET_PRODUCT=full_yk658_37m_lwtg_35g目录搜索KERNEL_DEFCONFIG
对应的是哪个文件

jdf@ubuntu:~/mtk_6737_6.x_wtwd_8_qiku_LE_PLUS/android/qiku/device/lentek/yk658_37m_lwtg_35g$ grep -nr KERNEL_DEFCONFIG 
lentek/yk658_37m_lwtg_35g/full_yk658_37m_lwtg_35g.mk:41:KERNEL_DEFCONFIG ?= yk658_37m_lwtg_35g_debug_defconfig
lentek/yk658_37m_lwtg_35g/full_yk658_37m_lwtg_35g.mk:43:KERNEL_DEFCONFIG ?= yk658_37m_lwtg_35g_defconfig

由此可以确认，需要修改kernel-3.18/arch/arm64/configs的以下文件，去默认打开驱动模块

yk658_37m_lwtg_35g_debug_defconfig
yk658_37m_lwtg_35g_defconfig

本地只修改改目录下defconfig文件，也可以生效，修改内容如下；如果修改后不生效，可以修改具体项目对应的配置文件

diff --git a/kernel-3.18/arch/arm64/configs/defconfig b/kernel-3.18/arch/arm64/configs/defconfig
old mode 100644
new mode 100755
index 9ce3d4b..5d72b88
--- a/kernel-4.9/arch/arm64/configs/defconfig
+++ b/kernel-4.9/arch/arm64/configs/defconfig
@@ -453,3 +453,5 @@ CONFIG_CRYPTO_GHASH_ARM64_CE=y
 CONFIG_CRYPTO_AES_ARM64_CE_CCM=y
 CONFIG_CRYPTO_AES_ARM64_CE_BLK=y
 CONFIG_CRYPTO_CRC32_ARM64=y
+CONFIG_HELLO=y

刷机验证

//查看驱动是否已经注册
root@yk658_37m_lwtg_35g:/ # cat /proc/devices  | grep hello
232 hello
//查看dev是否有hello驱动
root@yk658_37m_lwtg_35g:/ # ls -l /dev/hello
crw-rw-rw- root     root     232,   0 2015-01-01 00:45 hello

开发C可执行程序验证硬件驱动

创建验证程序

在源码\external\hello下面增加可执行文件
hello文件夹中包含两个文件

Android.mk
hello.c

Android.mk

LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := optional
LOCAL_SRC_FILES := hello.c
LOCAL_MODULE := hello
include $(BUILD_EXECUTABLE)

hello.c文件

#include <fcntl.h>
#include <stdio.h>
int main(void){
    char val = '1';
    int fd = open("/dev/hello",O_RDWR);
    read(fd,&val,1);
    printf("hello read fromc c:  %c\n",val);
    val = val+1;
    write(fd,&val,1);
    printf("hello write from c: %c\n",val);
    return 0;
}

添加模块到编译文件

为了在在整个系统编译的时候(比如make -j16)能够生成可执行文件，还需要修改/device/mediatek/common/device.mk文件，
添加PRODUCT_PACKAGES += PRODUCT_PACKAGES += hello

diff --git a/mediatek/common/device.mk b/mediatek/common/device.mk
index c4b078d..ca36221 100755
--- a/mediatek/common/device.mk
+++ b/mediatek/common/device.mk
@@ -47,6 +47,9 @@ endif
 
 #MTB
 PRODUCT_PACKAGES += mtk_setprop
+PRODUCT_PACKAGES += hello
+
 
 #MMS
 ifeq ($(strip $(MTK_BASIC_PACKAGE)), yes)

刷机验证

配置成功后，全编工程，刷入手机，在/system/bin目录就可以看到hello测试程序，运行查看效果

也可以只编译system.img文件(命令：：make snob，需要运行source build/envsetup.sh)

root@yk658_37m_lwtg_35g:/system/bin # hello
hello read fromc c:  1
hello write from c: 2
root@yk658_37m_lwtg_35g:/system/bin # hello
hello read fromc c:  2
hello write from c: 3
root@yk658_37m_lwtg_35g:/system/bin # hello
hello read fromc c:  3
hello write from c: 4
root@yk658_37m_lwtg_35g:/system/bin # hello
hello read fromc c:  4
hello write from c: 5
root@yk658_37m_lwtg_35g:/system/bin # hello
hello read fromc c:  5
hello write from c: 6

以上就是使用C语言编写的可执行程序来访问我们的Linux内核驱动程序；
接下来我们介绍，为改驱动程序增加HAL层代码，因为，最终，我们的驱动程序还是提供给Application层应用使用的