[Android Software/Hacking General [Developers Only]] llrraa2010:
HAL module for the driver

1. hello.h in hardware/libhardware/include/hardware

USER-NAME@MACHINE-NAME:~/Android$ cd hardware/libhardware/include/hardware

USER-NAME@MACHINE-NAME:~/Android/hardware/libhardware/include/hardware$ vi hello.h

#ifndef ANDROID_HELLO_INTERFACE_H

#define ANDROID_HELLO_INTERFACE_H

#include <hardware/hardware.h>

__BEGIN_DECLS

#define HELLO_HARDWARE_MODULE_ID "hello"

struct hello_module_t {

struct hw_module_t common;

};

struct hello_device_t {

struct hw_device_t common;

int fd;

int (*set_val)(struct hello_device_t* dev, int val);

int (*get_val)(struct hello_device_t* dev, int* val);

};

__END_DECLS

#endif

2. hello.c in hardware/libhardware/modules

#define LOG_TAG "HelloStub"

#include <hardware/hardware.h>

#include <hardware/hello.h>

#include <fcntl.h>

#include <errno.h>

#include <cutils/log.h>

#include <cutils/atomic.h>

#define DEVICE_NAME "/dev/hello"

#define MODULE_NAME "Hello"

#define MODULE_AUTHOR "shyluo@gmail.com"

/*open and close the device*/

static int hello_device_open(const struct hw_module_t* module, const char* name, struct hw_device_t** device);

static int hello_device_close(struct hw_device_t* device);

/*get and set the value*/

static int hello_set_val(struct hello_device_t* dev, int val);

static int hello_get_val(struct hello_device_t* dev, int* val);

static struct hw_module_methods_t hello_module_methods = {

open: hello_device_open

};

/*module info*/

struct hello_module_t HAL_MODULE_INFO_SYM = {

common: {

tag: HARDWARE_MODULE_TAG,

version_major: 1,

version_minor: 0,

id: HELLO_HARDWARE_MODULE_ID,

name: MODULE_NAME,

author: MODULE_AUTHOR,

methods: &hello_module_methods,

}

};

static int hello_device_open(const struct hw_module_t* module, const char* name, struct hw_device_t** device) {

struct hello_device_t* dev;dev = (struct hello_device_t*)malloc(sizeof(struct hello_device_t));

if(!dev) {

LOGE("Hello Stub: failed to alloc space");

return -EFAULT;

}

memset(dev, 0, sizeof(struct hello_device_t));

dev->common.tag = HARDWARE_DEVICE_TAG;

dev->common.version = 0;

dev->common.module = (hw_module_t*)module;

dev->common.close = hello_device_close;

dev->set_val = hello_set_val;dev->get_val = hello_get_val;

if((dev->fd = open(DEVICE_NAME, O_RDWR)) == -1) {

LOGE("Hello Stub: failed to open /dev/hello -- %s.", strerror(errno));free(dev);

return -EFAULT;

}

*device = &(dev->common);

LOGI("Hello Stub: open /dev/hello successfully.");

return 0;

}

static int hello_device_close(struct hw_device_t* device) {

struct hello_device_t* hello_device = (struct hello_device_t*)device;

if(hello_device) {

close(hello_device->fd);

free(hello_device);

}

return 0;

}

static int hello_set_val(struct hello_device_t* dev, int val) {

LOGI("Hello Stub: set value %d to device.", val);

write(dev->fd, &val, sizeof(val));

return 0;

}

static int hello_get_val(struct hello_device_t* dev, int* val) {

if(!val) {

LOGE("Hello Stub: error val pointer");

return -EFAULT;

}

read(dev->fd, val, sizeof(*val));

LOGI("Hello Stub: get value %d from device", *val);

return 0;

}

3. Android.mk

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_MODULE_TAGS := optional

LOCAL_PRELINK_MODULE := false

LOCAL_MODULE_PATH := $(TARGET_OUT_SHARED_LIBRARIES)/hw

LOCAL_SHARED_LIBRARIES := liblog

LOCAL_SRC_FILES := hello.c

LOCAL_MODULE := hello.default

include $(BUILD_SHARED_LIBRARY)

4. build

USER-NAME@MACHINE-NAME:~/Android$ mmm hardware/libhardware/modules/hello

you will get hello.default.so in out/target/product/generic/system/lib/hw

5. repack system.img

USER-NAME@MACHINE-NAME:~/Android$ make snod