版权声明：本文为博主原创文章，未经博主允许不得转载。如本文对您有帮助，欢迎点赞评论。 https://blog.csdn.net/sweetmilkcake/article/details/83217818
系统环境
博主已在Android 7.0上验证成功，其他后6.0，8.0，9.0应该改动不大，可以直接拿过来使用，底层基本不变，上层Android可能会有些接口调整，不过万变不离其中，也是可以参考的。
Demo原理
博主实现的Demo主要是通过外部串口来发送音量调整数据，给到Android，Android端的serial_comm进程会不断处理串口接收到的信息，然后再通过驱动进行InputEvent上报，触发PhoneWindowManager对上报的自定义按键进行处理，从而调整音量数据。这样处理通过InputEvent上报处理比较及时迅速。
Android系统层
Android上层需要修改这些文件，我直接diff出来了，其中我们新增的键值要注意不要跟系统的重复：KEYCODE_SPECIFIC_VOLUME = 280
diff --git a/android/frameworks/base/core/java/android/view/KeyEvent.java b/android/frameworks/base/core/java/android/view/KeyEvent.java
index b003f00..fabce16 100755
--- a/android/frameworks/base/core/java/android/view/KeyEvent.java
+++ b/android/frameworks/base/core/java/android/view/KeyEvent.java
@@ -809,6 +809,9 @@ public class KeyEvent extends InputEvent implements Parcelable {
public static final int KEYCODE_COPY = 278;
/** Key code constant: Paste key. */
public static final int KEYCODE_PASTE = 279;
+
+ public static final int KEYCODE_SPECIFIC_VOLUME = 280;
+
/** Key code constant: a shortcut key for mouse */
public static final int KEYCODE_MOUSE = 10009;
public static final int KEYCODE_TV_SYSTEM = 10000;
diff --git a/android/frameworks/base/core/res/res/values/attrs.xml b/android/frameworks/base/core/res/res/values/attrs.xml
index b61d6cf..4330802 100644
--- a/android/frameworks/base/core/res/res/values/attrs.xml
+++ b/android/frameworks/base/core/res/res/values/attrs.xml
@@ -1832,6 +1832,7 @@ i
<enum name="KEYCODE_CUT" value="277" />
<enum name="KEYCODE_COPY" value="278" />
<enum name="KEYCODE_PASTE" value="279" />
+ <enum name="KEYCODE_SPECIFIC_VOLUME" value="280" />
</attr>
<!-- ***************************************************************** -->
diff --git a/android/frameworks/native/include/android/keycodes.h b/android/frameworks/native/include/android/keycodes.h
index 4687b85..9fd76d5 100755
--- a/android/frameworks/native/include/android/keycodes.h
+++ b/android/frameworks/native/include/android/keycodes.h
@@ -758,6 +758,9 @@ enum {
AKEYCODE_COPY = 278,
/** Paste key. */
AKEYCODE_PASTE = 279,
+
+ AKEYCODE_SPECIFIC_VOLUME = 280,
+
// add for karaok by linjunqian
AKEYCODE_MIC_VOLUME_UP = 370,
AKEYCODE_MIC_VOLUME_DOWN = 371,
diff --git a/android/frameworks/native/include/input/InputEventLabels.h b/android/frameworks/native/include/input/InputEventLabels.h
index 911c568..78ed509 100755
--- a/android/frameworks/native/include/input/InputEventLabels.h
+++ b/android/frameworks/native/include/input/InputEventLabels.h
@@ -319,6 +319,7 @@ static const InputEventLabel KEYCODES[] = {
DEFINE_KEYCODE(CUT),
DEFINE_KEYCODE(COPY),
DEFINE_KEYCODE(PASTE),
+ DEFINE_KEYCODE(SPECIFIC_VOLUME),
DEFINE_KEYCODE(MIC_VOLUME_UP),
DEFINE_KEYCODE(MIC_VOLUME_DOWN),
DEFINE_KEYCODE(KOUT_VOLUME_UP),
diff --git a/android/frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java b/android/frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java
index a4408fc..fbcd7e0 100644
--- a/android/frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java
+++ b/android/frameworks/base/services/core/java/com/android/server/policy/PhoneWindowManager.java
@@ -5530,6 +5530,20 @@ public class PhoneWindowManager implements WindowManagerPolicy {
break;
}
+ case KeyEvent.KEYCODE_SPECIFIC_VOLUME: {
+ if (down) {
+ Log.d(TAG, "KeyEvent.KEYCODE_SPECIFIC_VOLUME down");
+ AudioManager audioManager = (AudioManager) mContext.getSystemService(Context.AUDIO_SERVICE);
+ audioManager.setStreamVolume(AudioManager.STREAM_MUSIC,
+ Integer.parseInt(SystemProperties.get("persist.sys.specific_volume")),
+ AudioManager.FLAG_SHOW_UI);
+ Log.d(TAG, "setStreamVolume " + SystemProperties.get("persist.sys.specific_volume"));
+ } else {
+ Log.d(TAG, "KeyEvent.KEYCODE_SPECIFIC_VOLUME up");
+ }
+ break;
+ }
+
case KeyEvent.KEYCODE_VOLUME_DOWN:
case KeyEvent.KEYCODE_VOLUME_UP:
case KeyEvent.KEYCODE_VOLUME_MUTE: {
到这里我们已经把上层的键值配好了，可以make systemimage -j8，烧进去进行测试，利用input keyevent 280，看看修改是否成功。
中间转换（Android - Linux）
Android自己定义了一套键值，Linux上报的键值需要通过kl文件转换才能正常识别。
diff --git a/android/frameworks/base/data/keyboards/Generic.kl b/android/frameworks/base/data/keyboards/Generic.kl
index 2a10bdd..ed9e1bd 100644
--- a/android/frameworks/base/data/keyboards/Generic.kl
+++ b/android/frameworks/base/data/keyboards/Generic.kl
@@ -247,6 +247,8 @@ key 224 BRIGHTNESS_DOWN
key 225 BRIGHTNESS_UP
key 226 HEADSETHOOK
+key 249 SPECIFIC_VOLUME
+
key 256 BUTTON_1
key 257 BUTTON_2
key 258 BUTTON_3
Linux底层
从下面可以看到，我们再Linux层定义的键值为#define KEY_SPECIFIC_VOLUME 249，这里我写了个虚拟按键的驱动程序，echo 1 > /sys/kernel/virtual_key，在往virtual_key节点写1的时候就会上报KEY_SPECIFIC_VOLUME键，从而通知Android上层进行处理。
diff --git a/lichee/linux-3.10/include/uapi/linux/input.h b/lichee/linux-3.10/include/uapi/linux/input.h
index 74b5a00..5413c97 100644
--- a/lichee/linux-3.10/include/uapi/linux/input.h
+++ b/lichee/linux-3.10/include/uapi/linux/input.h
@@ -473,6 +473,8 @@ struct input_keymap_entry {
#define KEY_MICMUTE 248 /* Mute / unmute the microphone */
+#define KEY_SPECIFIC_VOLUME 249
+
#define KEY_VOICE_ASSIST 582
/* Code 255 is reserved for special needs of AT keyboard driver */
diff --git a/lichee/linux-3.10/arch/arm64/configs/sun50iw6p1smp_android_7.x_defconfig b/lichee/linux-3.10/arch/arm64/configs/sun50iw6p1smp_android_7.x_defconfig
index 6d0ccaa..cc15e9a 100644
--- a/lichee/linux-3.10/arch/arm64/configs/sun50iw6p1smp_android_7.x_defconfig
+++ b/lichee/linux-3.10/arch/arm64/configs/sun50iw6p1smp_android_7.x_defconfig
@@ -1287,6 +1287,7 @@ CONFIG_INPUT_EVDEV=y
CONFIG_INPUT_KEYRESET=y
CONFIG_INPUT_KEYCOMBO=y
# CONFIG_INPUT_POWERKEY is not set
+CONFIG_INPUT_VIRTUALKEY=y
CONFIG_INPUT_SW_DEVICE=m
#
diff --git a/lichee/linux-3.10/drivers/input/Kconfig b/lichee/linux-3.10/drivers/input/Kconfig
index 77a12a9..9c6f668 100755
--- a/lichee/linux-3.10/drivers/input/Kconfig
+++ b/lichee/linux-3.10/drivers/input/Kconfig
@@ -205,6 +205,16 @@ config INPUT_POWERKEY
To compile this driver as a module,choose M here: the
module will be called sunxi-gpiokey.
+config INPUT_VIRTUALKEY
+ tristate "virtual key"
+ depends on INPUT
+ default n
+ ---help---
+ Say Y here if you want to support go virtual_key;
+
+ To compile this driver as a module,choose M here: the
+ module will be called virtual-key.
+
config INPUT_SW_DEVICE
tristate "i2c device detect support"
depends on INPUT && I2C
diff --git a/lichee/linux-3.10/drivers/input/Makefile b/lichee/linux-3.10/drivers/input/Makefile
index a7203f0..a66231a 100755
--- a/lichee/linux-3.10/drivers/input/Makefile
+++ b/lichee/linux-3.10/drivers/input/Makefile
@@ -18,6 +18,8 @@ obj-$(CONFIG_INPUT_EVDEV) += evdev.o
obj-$(CONFIG_INPUT_EVBUG) += evbug.o
obj-$(CONFIG_INPUT_POWERKEY) += sunxi-gpiokey.o
+obj-$(CONFIG_INPUT_VIRTUALKEY) += virtual-key.o
+obj-$(CONFIG_INPUT_VIRTUALKEY) += virtual-key-dev.o
obj-$(CONFIG_INPUT_KEYBOARD) += keyboard/
obj-$(CONFIG_INPUT_MOUSE) += mouse/
diff --git a/lichee/linux-3.10/drivers/input/virtual-key-dev.c b/lichee/linux-3.10/drivers/input/virtual-key-dev.c
new file mode 100644
index 0000000..60c8038
--- /dev/null
+++ b/lichee/linux-3.10/drivers/input/virtual-key-dev.c
@@ -0,0 +1,34 @@
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/platform_device.h>
+#include <linux/module.h>
+
+static struct platform_device virtual_key_dev = {
+ .name = "virtual_key",
+ .id = -1,
+};
+
+static int __init virtual_key_dev_init(void)
+{
+ printk("%s-%d: enter\n", __FUNCTION__, __LINE__);
+ if (platform_device_register(&virtual_key_dev)) {
+ pr_err("virtual_key virtual_key_dev_init fail\n");
+ return -1;
+ }
+
+ return 0;
+}
+
+static void __exit virtual_key_dev_exit(void)
+{
+ platform_device_unregister(&virtual_key_dev);
+}
+
+module_init(virtual_key_dev_init);
+module_exit(virtual_key_dev_exit);
+
+MODULE_AUTHOR("sweetmilkcake <[email protected]>");
+MODULE_DESCRIPTION("virtual key dev");
+MODULE_LICENSE("GPL");
+
+
diff --git a/lichee/linux-3.10/drivers/input/virtual-key.c b/lichee/linux-3.10/drivers/input/virtual-key.c
new file mode 100644
index 0000000..0b951d2
--- /dev/null
+++ b/lichee/linux-3.10/drivers/input/virtual-key.c
@@ -0,0 +1,151 @@
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/input.h>
+#include <linux/delay.h>
+#include <linux/slab.h>
+#include <linux/interrupt.h>
+#include <linux/keyboard.h>
+#include <linux/ioport.h>
+#include <linux/timer.h>
+#include <linux/clk.h>
+#include <linux/sys_config.h>
+#include <linux/sys_config.h>
+#include <linux/platform_device.h>
+#include <linux/power/scenelock.h>
+
+static volatile u32 virtual_key_trigger;
+static struct mutex virtual_key_mutex;
+static struct input_dev *virtual_key_dev;
+
+static ssize_t virtual_key_show(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ char *buf)
+{
+ return sprintf(buf, "%d\n", virtual_key_trigger);
+}
+
+static ssize_t virtual_key_store(struct kobject *kobj,
+ struct kobj_attribute *attr,
+ const char *buf, size_t count)
+{
+ int ret = 0;
+
+ mutex_lock(&virtual_key_mutex);
+
+ switch (buf[0]) {
+ case '0':
+ virtual_key_trigger = 0;
+ break;
+ case '1':
+ virtual_key_trigger = 1;
+ input_report_key(virtual_key_dev, KEY_SPECIFIC_VOLUME, 1);
+ input_sync(virtual_key_dev);
+ input_report_key(virtual_key_dev, KEY_SPECIFIC_VOLUME, 0);
+ input_sync(virtual_key_dev);
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ mutex_unlock(&virtual_key_mutex);
+ return ret < 0 ? ret : count;
+}
+
+static struct kobj_attribute virtual_key_attr = __ATTR(virtual_key,
+ 0666, virtual_key_show,
+ virtual_key_store);
+
+static int virtual_key_probe(struct platform_device *pdev)
+{
+ int err = 0;
+
+ printk("%s-%d: enter\n", __FUNCTION__, __LINE__);
+
+ virtual_key_dev = input_allocate_device();
+ if (!virtual_key_dev) {
+ pr_err("virtual_key: not enough memory for input device\n");
+ err = -ENOMEM;
+ goto fail1;
+ }
+
+ virtual_key_dev->name = "virtual_key";
+ //virtual_key_dev->phys = "sunxikbd/input0";
+ virtual_key_dev->id.bustype = BUS_HOST;
+ virtual_key_dev->id.vendor = 0x0001;
+ virtual_key_dev->id.product = 0x0001;
+ virtual_key_dev->id.version = 0x0100;
+
+#ifdef REPORT_REPEAT_KEY_BY_INPUT_CORE
+ virtual_key_dev->evbit[0] = BIT_MASK(EV_KEY)|BIT_MASK(EV_REP);
+ printk(KERN_DEBUG "REPORT_REPEAT_KEY_BY_INPUT_CORE is defined, support report repeat key value. \n");
+#else
+ virtual_key_dev->evbit[0] = BIT_MASK(EV_KEY);
+#endif
+ set_bit(KEY_SPECIFIC_VOLUME, virtual_key_dev->keybit);
+ mutex_init(&virtual_key_mutex);
+
+ err = input_register_device(virtual_key_dev);
+ if (err)
+ goto fail2;
+
+ err = sysfs_create_file(kernel_kobj, &virtual_key_attr.attr);
+ if (err) {
+ printk(KERN_ERR "virtual_key: unable to create sysfs file"
+ " virtual_key (%d)\n", err);
+ goto fail3;
+ }
+
+ return 0;
+
+fail3:
+ input_unregister_device(virtual_key_dev);
+fail2:
+ input_free_device(virtual_key_dev);
+fail1:
+ printk(KERN_DEBUG "virtual_key_init failed. \n");
+
+ return err;
+}
+
+static int virtual_key_remove(struct platform_device *dev)
+{
+
+ input_unregister_device(virtual_key_dev);
+
+ return 0;
+}
+
+static struct platform_driver virtual_key_driver = {
+ .probe = virtual_key_probe,
+ .remove = virtual_key_remove,
+ .driver = {
+ .name = "virtual_key",
+ .owner = THIS_MODULE,
+ },
+};
+
+static int __init virtual_key_init(void)
+{
+ printk("%s-%d: enter\n", __FUNCTION__, __LINE__);
+ if (platform_driver_register(&virtual_key_driver)) {
+ pr_err("virtual_key platform_driver_register fail\n");
+ return -1;
+ }
+
+ return 0;
+}
+
+static void __exit virtual_key_exit(void)
+{
+ platform_driver_unregister(&virtual_key_driver);
+}
+
+module_init(virtual_key_init);
+module_exit(virtual_key_exit);
+
+MODULE_AUTHOR("sweetmilkcake <[email protected]>");
+MODULE_DESCRIPTION("virtual key driver");
+MODULE_LICENSE("GPL");
+
+
serial_comm程序
这个程序其实在另一篇文章已经介绍过，这里我把它放到system/core目录，打包到系统中，注意要在device.mk里面定义，不然全编的时候是不会编到系统的。
diff --git a/android/device/softwinner/petrel-p1/device.mk b/android/device/softwinner/petrel-p1/device.mk
index 6cb1831..9696939 100755
--- a/android/device/softwinner/petrel-p1/device.mk
+++ b/android/device/softwinner/petrel-p1/device.mk
@@ -60,6 +60,8 @@ PRODUCT_PACKAGES += \
libip_loader \
iploader_server
+PRODUCT_PACKAGES += serial_comm
+
PRODUCT_COPY_FILES += \
device/softwinner/petrel-p1/configs/virtual-remote.kl:system/usr/keylayout/virtual-remote.kl \
device/softwinner/petrel-p1/configs/sunxi-keyboard.kl:system/usr/keylayout/sunxi-keyboard.kl \
diff --git a/android/system/core/serial_comm/Android.mk b/android/system/core/serial_comm/Android.mk
new file mode 100644
index 0000000..d7ee151
--- /dev/null
+++ b/android/system/core/serial_comm/Android.mk
@@ -0,0 +1,9 @@
+LOCAL_PATH := $(call my-dir)
+
+include $(CLEAR_VARS)
+LOCAL_MODULE := serial_comm
+LOCAL_SRC_FILES := serial_comm.c
+LOCAL_CFLAGS := -Wall -Werror -Wno-unused-parameter
+LOCAL_SHARED_LIBRARIES := \
+ libcutils
+include $(BUILD_EXECUTABLE)
diff --git a/android/system/core/serial_comm/serial_comm.c b/android/system/core/serial_comm/serial_comm.c
new file mode 100644
index 0000000..f40526f
--- /dev/null
+++ b/android/system/core/serial_comm/serial_comm.c
@@ -0,0 +1,212 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/ioctl.h>
+#include <errno.h>
+#include <unistd.h>
+#include <termios.h>
+
+#include <linux/ioctl.h>
+
+#include <cutils/properties.h>
+
+// dev control date end
+// 02 01 12 7F
+#define SERIAL_REC_NUM 4
+// VTIME and VMIN is very important.
+// VTIME: Time to wait for data (tenths of seconds)
+#define SERIAL_VTIME 1
+// VMIN: Minimum number of characters to read
+#define SERIAL_VMIN SERIAL_REC_NUM
+
+int serial_set(int fd, int speed, int bits, int event, int stop) {
+ struct termios ttys;
+
+ memset(&ttys, 0, sizeof(ttys));
+
+ // Enable the receiver and set local mode
+ // CLOCAL: Local line - do not change "owner" of port
+ // CREAD: Enable receiver
+ ttys.c_cflag |= (CLOCAL | CREAD);
+
+ // Mask the character size bits
+ // CSIZE: Bit mask for data bits
+ ttys.c_cflag &= ~CSIZE;
+
+ switch (speed) {
+ case 9600:
+ // B9600: 9600 baud
+ cfsetispeed(&ttys, B9600);
+ cfsetospeed(&ttys, B9600);
+ break;
+ case 115200:
+ // B115200: 115,200 baud
+ cfsetispeed(&ttys, B115200);
+ cfsetospeed(&ttys, B115200);
+ break;
+ default:
+ cfsetispeed(&ttys, B115200);
+ cfsetospeed(&ttys, B115200);
+ break;
+ }
+
+ switch (bits) {
+ case 7:
+ // 7 data bits
+ ttys.c_cflag |= CS7;
+ break;
+ case 8:
+ // 8 data bits
+ ttys.c_cflag |= CS8;
+ break;
+ default:
+ ttys.c_cflag |= CS8;
+ break;
+ }
+
+ switch (event) {
+ case 'o':
+ case 'O':
+ // PARENB: Enable parity bit
+ ttys.c_cflag |= PARENB;
+ // INPCK: Enable parity check
+ // ISTRIP: Strip parity bits
+ ttys.c_cflag |= (INPCK | ISTRIP);
+ // PARODD: Use odd parity instead of even
+ ttys.c_cflag |= PARODD;
+ break;
+ case 'e':
+ case 'E':
+ ttys.c_cflag |= PARENB;
+ ttys.c_cflag |= (INPCK | ISTRIP);
+ ttys.c_cflag &= ~PARODD;
+ break;
+ case 'n':
+ case 'N':
+ ttys.c_cflag &= ~PARENB;
+ break;
+ default:
+ ttys.c_cflag &= ~PARENB;
+ break;
+ }
+
+ switch (stop) {
+ case 1:
+ // CSTOPB: 2 stop bits (1 otherwise)
+ ttys.c_cflag &= ~CSTOPB;
+ break;
+ case 2:
+ ttys.c_cflag |= CSTOPB;
+ break;
+ default:
+ ttys.c_cflag &= ~CSTOPB;
+ break;
+ }
+
+ // VTIME: Time to wait for data (tenths of seconds)
+ ttys.c_cc[VTIME] = SERIAL_VTIME;
+ // VMIN: Minimum number of characters to read
+ ttys.c_cc[VMIN] = SERIAL_VMIN;
+
+ // Hardware flow control using the CTS (Clear To Send) and RTS (Request To Send) signal lines
+ // CNEW_RTSCTS, CRTSCTS: Enable hardware flow control (not supported on all platforms)
+ // CNEW_RTSCTS: Also called CRTSCTS
+ //ttys.c_cflag |= CRTSCTS; // Enable hardware flow control
+ ttys.c_cflag &= ~CRTSCTS; // Disable hardware flow control
+
+ // Choosing Canonical Input
+ // Canonical input is line-oriented. Input characters are put into a buffer
+ // which can be edited interactively by the user until a CR (carriage return)
+ // or LF (line feed) character is received.
+ // When selecting this mode you normally select the ICANON, ECHO, and ECHOE options
+ //ttys.c_lflag |= (ICANON | ECHO | ECHOE);
+
+ // Choosing Raw Input
+ // Raw input is unprocessed. Input characters are passed through exactly as they are received,
+ // when they are received. Generally you'll deselect the ICANON, ECHO, ECHOE, and ISIG options when using raw input
+ ttys.c_lflag &= ~(ICANON | ECHO | ECHOE | ISIG);
+
+ // OPOST: Postprocess output (not set = raw output)
+ //ttys.c_oflag |= OPOST; // Choosing Processed Output
+ ttys.c_oflag &= ~OPOST; // Choosing Raw Output
+
+
+ // Flushes the input and/or output queue.
+ // TCIFLUSH: flushes data received but not read.
+ // TCOFLUSH: flushes data written but not transmitted.
+ // TCIOFLUSH: flushes both data received but not read, and data written but not transmitted.
+ tcflush(fd, TCIOFLUSH);
+
+ // Sets the serial port settings immediately.
+ // TCSANOW: Make changes now without waiting for data to complete
+ // TCSADRAIN: Wait until everything has been transmitted
+ // TCSAFLUSH: Flush input and output buffers and make the change
+ if (tcsetattr(fd, TCSANOW, &ttys) != 0) {
+ perror("serial set fail!\n");
+ return -2;
+ }
+
+ return 0;
+}
+
+int is_data_valid(unsigned char *buf) {
+ if (buf[3] != 0x7f) {
+ fprintf(stderr, "%s, data is not valid!\n", __FUNCTION__);
+ return -1;
+ }
+ return 0;
+}
+
+int main(int argc, char *argv[]) {
+ int fd = 0;
+ int ret = 0;
+ int n = 0;
+ unsigned char buf[SERIAL_REC_NUM];
+ char str[10];
+
+ printf("serial test start.\n");
+
+ fd = open("/dev/ttyS3", O_RDWR | O_NOCTTY);
+ if (fd < 0) {
+ fprintf(stderr, "%s, open serial failed!\n", __FUNCTION__);
+ return -1;
+ }
+
+ // Baud rate: 115200, Data bits: 8, Parity: None, Stop bits: 1
+ ret = serial_set(fd, 115200, 8, 'N', 1);
+ if (ret) {
+ fprintf(stderr, "%s, serial set failed!\n", __FUNCTION__);
+ return -1;
+ }
+
+ while (1) {
+ memset(&buf, 0, sizeof(buf));
+ // blocking here
+ n = read(fd, &buf, SERIAL_REC_NUM);
+ if (n < SERIAL_REC_NUM) {
+ fprintf(stderr, "serial read fail!, n = %d\n", n);
+ } else {
+ printf("buf[0] = 0x%x, buf[1] = 0x%x, buf[2] = 0x%x, buf[3] = 0x%x, \n",
+ buf[0], buf[1], buf[2], buf[3]);
+
+ if (!is_data_valid(buf)) {
+ // data is ok
+ snprintf(str, 3, "%d", buf[2]);
+ printf("property_set persist.sys.specific_volume = %s\n", str);
+ property_set("persist.sys.specific_volume", str);
+ }
+ //n = write(fd, &buf, SERIAL_REC_NUM);
+ //if (n < SERIAL_REC_NUM) {
+ // fprintf(stderr, "serial write fail!, n = %d\n", n);
+ //}
+ }
+ }
+
+ close(fd);
+
+ printf("serial test end.\n");
+ return 0;
+}
init进程触发逻辑
这里的逻辑是，当serial_comm进程收到串口消息会设置persist.sys.specific_volume属性，然后init进程会往/sys/kernel/virtual_key写1，然后驱动会上报键值，通知Android层，再到PhoneWindowManager进行处理。这里还要注意Selinux规则的报错，并且改了之后要全编system才可以，当时我也是调了好久。。。
petrel-p1:/ # dmesg | grep serial
[ 0.000000] Kernel command line: earlyprintk=sunxi-uart,0x05000000 initcall_debug=0 console=ttyS0,115200 loglevel=1 root=/dev/mmcblk0p7 init=/init partitions=bootloader@mmcblk0p2:env@mmcblk0p5:boot@mmcblk0p6:system@mmcblk0p7:verity_block@mmcblk0p8:misc@mmcblk0p9:recovery@mmcblk0p10:sysrecovery@mmcblk0p11:private@mmcblk0p12:alog@mmcblk0p13:Reserve0@mmcblk0p14:Reserve1@mmcblk0p15:Reserve2@mmcblk0p16:cache@mmcblk0p17:UDISK@mmcblk0p1 cma=64M mac_addr=00:00:00:00:00:00 wifi_mac= bt_mac= selinux=1 specialstr= androidboot.selinux=permissive androidboot.serialno=dc000141091d6413078b boot_type=1 androidboot.hardware=sun50iw6p1
[ 0.822916] usbcore: registered new interface driver usbserial
[ 0.823153] usbserial: USB Serial support registered for GSM modem (1-port)
[ 2.700573] usb_serial_number:20080411
[ 6.362876] init: Service serial_comm does not have a SELinux domain defined.
[ 7.376520] init: Service serial_comm does not have a SELinux domain defined.
diff --git a/android/device/softwinner/petrel-common/sepolicy/file_contexts b/android/device/softwinner/petrel-common/sepolicy/file_contexts
index 07a6984..5414c04 100755
--- a/android/device/softwinner/petrel-common/sepolicy/file_contexts
+++ b/android/device/softwinner/petrel-common/sepolicy/file_contexts
@@ -65,3 +65,4 @@
# optee
/dev/opteearmtz00 u:object_r:tee_device:s0
/system/bin/tee_supplicant u:object_r:optee_exec:s0
+/system/bin/serial_comm u:object_r:serial_comm_exec:s0
diff --git a/android/device/softwinner/petrel-common/sepolicy/serial_comm.te b/android/device/softwinner/petrel-common/sepolicy/serial_comm.te
new file mode 100644
index 0000000..fc0caeb
--- /dev/null
+++ b/android/device/softwinner/petrel-common/sepolicy/serial_comm.te
@@ -0,0 +1,5 @@
+type serial_comm, domain;
+type serial_comm_exec, exec_type, file_type;
+init_daemon_domain(serial_comm);
+allow serial_comm sysfs:file rw_file_perms;
+
diff --git a/android/device/softwinner/petrel-p1/init.sun50iw6p1.rc b/android/device/softwinner/petrel-p1/init.sun50iw6p1.rc
index 6d98d7a..7d99616 100755
--- a/android/device/softwinner/petrel-p1/init.sun50iw6p1.rc
+++ b/android/device/softwinner/petrel-p1/init.sun50iw6p1.rc
@@ -113,6 +113,8 @@ on boot
write /dev/cpuset/system-background/cpus 0-3
write /dev/cpuset/top-app/cpus 0-3
+ start serial_comm
+
on property:sys.shutdown.hdmi=1
write /sys/class/hdmi/hdmi/attr/hpd_mask 0x10
@@ -288,3 +290,12 @@ service stop_pppoe /system/bin/pppoe-disconnect
service optee /system/bin/tee_supplicant
class main
oneshot
+
+service serial_comm /system/bin/serial_comm
+ class main
+ user root
+ disabled
+ oneshot
+
+on property:persist.sys.specific_volume=*
+ write /sys/kernel/virtual_key 1
测试
通过串口发送数据，可以直接修改Android层的音量，大功告成。
完整补丁
补丁放在：https://github.com/sweetmilkcake/AndroidPatches/blob/master/virtual-key/virtual-key.diff