mtk平台sensor分析一：alsps框架下的光距感驱动流程

一、前言

mtk平台为了方便光距感驱动的兼容和统一管理，将所有的光距感驱动程序都放置在alsps框架中；
本文以MT8183平台alsps框架下的光距感ltr559为例进行分析；

 涉及文件及目录：设备树：   kernel-4.4/arch/arm64/boot/dts/mediatek/mt6771.dts   kernel-4.4/arch/arm64/boot/dts/mediatek/k71v1_64_bsp.dtsalsps架构：kernel-4.4/drivers/misc/mediatek/sensors-1.0/alsps/alsps.ckernel-4.4/drivers/misc/mediatek/sensors-1.0/hwmon/sensor_attributes/sensor_attr.c光距感驱动：kernel-4.4/drivers/misc/mediatek/sensors-1.0/alsps/LTR559/ltr559.c

二、alsps框架分析

1、驱动加载顺序

ltr599.c和alsps.c驱动程序在内核初始化过程中的调用顺序跟两者选择加载入口函数的方式有关；
ltr599.c：module_init(ltr559_init);
alsps.c：late_initcall(alsps_init);
从kernel-4.4/include/linux/init.h文件中可以获取启动顺序的宏列表和排序；

#define early_initcall(fn)       __define_initcall(fn, early)
#define pure_initcall(fn)       __define_initcall(fn, 0)
#define core_initcall(fn)       __define_initcall(fn, 1)
#define core_initcall_sync(fn)      __define_initcall(fn, 1s)
#define postcore_initcall(fn)       __define_initcall(fn, 2)
#define postcore_initcall_sync(fn)  __define_initcall(fn, 2s)
#define arch_initcall(fn)       __define_initcall(fn, 3)
#define arch_initcall_sync(fn)      __define_initcall(fn, 3s)
#define subsys_initcall(fn)     __define_initcall(fn, 4)
#define subsys_initcall_sync(fn)    __define_initcall(fn, 4s)
#define fs_initcall(fn)         __define_initcall(fn, 5)
#define fs_initcall_sync(fn)        __define_initcall(fn, 5s)
#define rootfs_initcall(fn)     __define_initcall(fn, rootfs)
#define device_initcall(fn)     __define_initcall(fn, 6)
#define device_initcall_sync(fn)    __define_initcall(fn, 6s)
#define late_initcall(fn)       __define_initcall(fn, 7)
#define late_initcall_sync(fn)      __define_initcall(fn, 7s

module_init对应默认的device_initcall，比late_initcall数字小，数字越小的优先级越高；所以内核初始化调用顺序是先调用ltr559.c入口函数后调用alsps.c的入口函数；

2、sensor内核初始化驱动流程

机器刚开始启动进入kernel初始化阶段时，光距感sensor驱动流程:

先调用ltr559.c文件中的ltr559_init，在alsps_driver_add函数中先向内核平台总线注册一个als_ps_driver结构体的设备驱动:platform_driver_register(&als_ps_driver))，之后将所有加载过的光距感驱动程序通过调用alsps_driver_add(obj);函数,将alsps_init_list[MAX_CHOOSE_ALSPS_NUM]数组中的成员都指向对应的obj；

//ltr599.c
static struct alsps_init_info ltr559_init_info = {.name = LTR559_DEV_NAME,.init = alsps_local_init,.uninit = alsps_remove,};
static int __init ltr559_init(void)
{alsps_driver_add(&ltr559_init_info);return 0；
}

//mt6771.dts
//配置alsps架构下的device信息
alsps:als_ps@0 {compatible = "mediatek,als_ps";
};

//alsps.c
static const struct of_device_id als_ps_of_match[] = {{.compatible = "mediatek,als_ps",},
};
static struct platform_driver als_ps_driver = {.probe = als_ps_probe,.remove = als_ps_remove,.driver = {.name = "als_ps",.of_match_table = als_ps_of_match,}
};
int alsps_driver_add(struct alsps_init_info *obj)
{int err = 0;int i = 0;for (i = 0; i < MAX_CHOOSE_ALSPS_NUM; i++) {  //MAX_CHOOSE_ALSPS_NUM = 5if ((i == 0) && (alsps_init_list[0] == NULL))   if (platform_driver_register(&als_ps_driver))if (alsps_init_list[i] == NULL) {obj->platform_diver_addr = &als_ps_driver;alsps_init_list[i] = obj; break;}}//光距感驱动遍历数量超过5（MAX_CHOOSE_ALSPS_NUM）个时会报错if (i >= MAX_CHOOSE_ALSPS_NUM) {pr_err("ALSPS driver add err\n");err = -1;}return err;
}

当alsps_init_list数组成员与所有的光距感obj绑定后，开始运行alsps.c中alsps_init->alsps_probe->alsps_real_driver_init->alsps_init_list[i]->init();, 通过操作alsps_init_list数组成员的init函数指针来运行对应光距感驱动程序中的obj结构体init指针函数，如ltr559.c中的alsps_local_init函数；

之后的流程就很熟悉了，向i2c平台注册了ltr559_i2c_driver，当alsps_of_match中的compatible与dts中compatible的属性保持一致就会调用ltr559_i2c_probe；

//k71v1_64_bsp.dts
&i2c1 {alsps1@3b{compatible = "mediatek,alsps559";reg = <0x3b>;};
}

//ltr559.c
static const struct of_device_id alsps_of_match[] = {{.compatible = "mediatek,alsps559"},{},
};
static struct i2c_driver ltr559_i2c_driver = { .probe      = ltr559_i2c_probe, .of_match_table = alsps_of_match, ...
};
static int alsps_local_init(void)
{i2c_add_driver(&ltr559_i2c_driver); //注册i2c总线下的platform_driver
}

以光感为例，在ltr559_i2c_probe函数中会执行以下内容：
1、完成光感硬件初始化（不涉及alsps架构，第三章节再讲）；
2、完成光感功能控制，注册光感设备，创建设备节点：als_register_control_path；
3、添加与alsps框架文件中的数据传输函数：als_register_data_path；

2.1 分析als_register_control_path函数

在als_register_control_path函数中实现了两个功能：
1、alsps.c中alsps架构下的通用功能函数与ltr559.c中的als_ctl结构体成员绑定，通过这个联系在alsps.c中可以控制ltr559光感的使能开关，同时也可以读到ltr559.c文件是否选择alsps架构的数据上报功能等；

//ltr559.c
static int ltr559_i2c_probe(struct i2c_client *client, const struct i2c_device_id *id)
{struct als_control_path als_ctl={0};als_ctl.open_report_data= als_open_report_data;//没用到als_ctl.enable_nodata = ltr559_als_power; //是否使能ltr559光感 ...als_ctl.is_report_input_direct = false;//false表示不直接上报数据，走alsps架构流程als_register_control_path(&als_ctl);
}//alsps.c
int als_register_control_path(struct als_control_path *ctl)
{cxt = alsps_context_obj;//1、功能函数绑定cxt->als_ctl.open_report_data = ctl->open_report_data; cxt->als_ctl.enable_nodata = ctl->enable_nodata;...cxt->als_ctl.is_report_input_direct = ctl->is_report_input_direct;//2、注册设备节点als_misc_init(alsps_context_obj);sysfs_create_group(&alsps_context_obj->als_mdev.this_device->kobj,&als_attribute_group);kobject_uevent(&alsps_context_obj->als_mdev.this_device->kobj,KOBJ_ADD); return 0;
}

2、创建注册光感设备节点:/dev/m_als_misc,提供给上层获取数据的fops结构体；

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sensor_attr.c

alsps.c

ltr599.c

device_create

als_misc_init

sensor_attr_register

ltr559_i2c_probe

als_register_control_path

//alsps.c
static const struct file_operations light_fops = {.owner = THIS_MODULE,.open = light_open,.read = light_read,.poll = light_poll,
};
#define ALS_MISC_DEV_NAME "m_als_misc"
static int als_misc_init(struct alsps_context *cxt)
{cxt->als_mdev.minor = ID_LIGHT;cxt->als_mdev.name = ALS_MISC_DEV_NAME;cxt->als_mdev.fops = &light_fops;sensor_attr_register(&cxt->als_mdev);}
//sensor_attr.c
int sensor_attr_register(struct sensor_attr_t *misc)
{list_for_each_entry(c, &sensor_attr_list, list) //主设备号：sensor_attr_major； 次设备号：misc->minordev = MKDEV(sensor_attr_major, misc->minor);//根据dev生成的设备号，创建光距感字符设备节点：/dev/m_als_miscmisc->this_device = device_create(sensor_attr_class, misc->parent, dev,misc, "%s", misc->name);  //misc->name = "m_als_misc"list_add(&misc->list, &sensor_attr_list);  //将misc->list放入内核sensor_attr_list链表中；sensor_event_register(misc->minor);  //后续再分析
}

2.2 分析als_register_data_path函数

als_register_data_path函数的功能主要是在alsps.c文件中通过操作get_data函数指针可以获取ltr559.c文件中的光感值；

//ltr559.c
static int ltr559_i2c_probe(struct i2c_client *client, const struct i2c_device_id *id)
{als_data.get_data = ltr559_als_read; //ltr559_als_read函数的功能就是将光感芯片感应到的数据通过i2c方式读取出来，然后将该函数的参数指向这个获取值；als_data.vender_div = 100;als_register_data_path(&als_data);
}//alsps.c
int als_register_data_path(struct als_data_path *data)
{struct alsps_context *cxt = NULL;cxt = alsps_context_obj;cxt->als_data.get_data = data->get_data;//get_data为获取光感函数指针cxt->als_data.vender_div = data->vender_div;if (cxt->als_data.get_data == NULL) return -1;return 0;
}

3、alsps框架下sys节点控制sensor操作流程

光距感的使能开关和数据上报都是hal层通过操作sys节点来控制的，下面以光感als为例进行分析；

3.1 初始化读取光感数据的定时器timer_als

alsps初始化时定义一个光感定时器timer_als（这个定时器初始化阶段没有启动），当定时器启动时先获取光感值再将数据上报，并每隔一段时间（默认为200ms）循环采集和上报数据；

//alsps.c
/*当timer_als定时器被触发后，超时后会调用工作队列中的als_work_func函数；
功能：1、获取ltr559.c中感应到的光感值；2、将光感值放置缓存buffer中，等待应用层读取；3、修改定时器时间，保证定时器循环不断超时触发；
*/
static void als_work_func(struct work_struct *work)
{cxt->als_data.get_data(&value, &status);  //获取ltr559.c文件中读取到的光感值；als_data_report(cxt->drv_data.als_data.values[0],cxt->drv_data.als_data.status);//上报数据mod_timer(&cxt->timer_als,jiffies + atomic_read(&cxt->delay_als) / (1000 / HZ));//修改定时器时间间隔（&cxt->delay_als）ms并启动
}
//当定时器timer_als超时时会调用als_poll函数
static void als_poll(unsigned long data)
{//将任务提交到工作队列中schedule_work(&obj->report_als);
}static struct alsps_context *alsps_context_alloc_object(void)
{atomic_set(&obj->delay_als, 200);  //obj->delay_als = 200INIT_WORK(&obj->report_als, als_work_func); //初始化工作队列init_timer(&obj->timer_als);//初始化timer_als定时器obj->timer_als.expires  = jiffies + atomic_read(&obj->delay_als)/(1000/HZ);obj->timer_als.function  = als_poll;obj->timer_als.data  = (unsigned long)obj;//下面这些参数值会作为是否启动定时器的先决条件判断obj->is_als_first_data_after_enable = false;obj->is_als_polling_run = false;obj->is_als_batch_enable = false;obj->als_power = 0;obj->als_enable = 0;obj->als_delay_ns = -1;obj->als_rgb_delay_ns = -1;obj->als_latency_ns = -1;
}

3.2 触发定时器timer_als的流程

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alsps.c

满足条件A

满足条件B

als_store_active

als_store_batch

als_enable_and_batch

mod_timer<&cxt->timer_als>

del_timer_sync<&cxt->timer_als>

timer_als定时器触发是通过alsps.c文件中alsactive和alsbatch两个节点的写函数来控制的:als_store_active、als_store_batch；

3.2.1 在als_enable_and_batch函数中启动timer_als定时器的满足条件A：

1、cxt->als_power == 0 && cxt->als_enable == 1
==>cxt->als_power默认初始值为0，cxt->als_enable在als_store_active函数有设置；
2、cxt->als_delay_ns >= 0
==>在als_store_batch函数中有设置
3、cxt->als_ctl.is_report_input_direct == false
==>根据ltr559.c中的ctl->is_report_input_direct的变量决定的；
4、cxt->is_als_polling_run == false
==>默认初始值为false，满足条件；

在ltr559.c中的is_report_input_direct默认设置为false的情况下：
echo 4，0，200000000，0 > /sys/class/sensor/m_als_misc/alsbatch，设置als_delay_ns=200000000 //200ms
echo 4，1 > /sys/class/sensor/m_als_misc/alsactive,设置als_enable =1；
满足条件A,打开定时器上报数据；

3.2.2 在als_enable_and_batch函数中取消timer_als定时器的满足条件B：

1、cxt->als_power == 1 && cxt->als_enable == 0
2、cxt->als_ctl.is_report_input_direct == false && cxt->is_als_polling_run == true

当timer_als定时器打开时，第二个条件已经满足了，只需要将als_enable =0就能关闭定时器；
echo 4，0 > /sys/class/sensor/m_als_misc/alsactive

//alsps.c
static ssize_t als_store_active(struct device *dev,struct device_attribute *attr, const char *buf,size_t count)
{sscanf(buf, "%d,%d", &handle, &en);if (handle == ID_LIGHT) { //ID_LIGHT = 4if (en) {cxt->als_enable = 1;last_als_report_data = -1;} else if (!en) {cxt->als_enable = 0;}als_enable_and_batch();
}
//alsps.c
static ssize_t als_store_batch(struct device *dev,struct device_attribute *attr, const char *buf,size_t count)
{sscanf(buf, "%d,%d,%lld,%lld", &handle, &flag, &delay_ns, &latency_ns);if (handle == ID_LIGHT) { //ID_LIGHT = 4cxt->als_delay_ns = delay_ns;cxt->als_latency_ns = latency_ns;err = als_enable_and_batch();} else if (handle == ID_RGBW) { //ID_RGBW = 69cxt->als_rgb_delay_ns = delay_ns;cxt->rgbw_latency_ns = latency_ns;}
}
DEVICE_ATTR(alsactive,      S_IWUSR | S_IRUGO, als_show_active, als_store_active);
DEVICE_ATTR(alsbatch,       S_IWUSR | S_IRUGO, als_show_batch,  als_store_batch);

//alsps.c
static int als_enable_and_batch(void)
{mod_timer(&cxt->timer_als,jiffies +atomic_read(&cxt->delay_als) /(1000 / HZ));
}static int als_enable_and_batch(void)
{/* als_power on -> power off */if (cxt->als_power == 1 && cxt->als_enable == 0) {if (cxt->als_ctl.is_report_input_direct == false &&cxt->is_als_polling_run == true) {del_timer_sync(&cxt->timer_als);  //删除timer_als光感定时器cancel_work_sync(&cxt->report_als);cxt->drv_data.als_data.values[0] = ALSPS_INVALID_VALUE;cxt->is_als_polling_run = false;}cxt->als_ctl.enable_nodata(0);cxt->als_power = 0;cxt->als_delay_ns = -1;return 0;}/* als_power off -> power on */if (cxt->als_power == 0 && cxt->als_enable == 1) {cxt->als_ctl.enable_nodata(1);cxt->als_power = 1;}if (cxt->als_power == 1 && cxt->als_delay_ns >= 0) {     if (cxt->als_ctl.is_support_batch)cxt->als_ctl.batch(0, cxt->als_delay_ns,cxt->als_latency_ns);elsecxt->als_ctl.batch(0, cxt->als_delay_ns, 0);           if (cxt->als_ctl.is_report_input_direct == false) {int mdelay = cxt->als_delay_ns;do_div(mdelay, 1000000);atomic_set(&cxt->delay_als, mdelay);if (cxt->is_als_polling_run == false) {mod_timer(&cxt->timer_als,jiffies +atomic_read(&cxt->delay_als) /(1000 / HZ));//设置timer_als光感定时器的时间间隔并启动cxt->is_als_polling_run = true;cxt->is_als_first_data_after_enable = true;}}}return 0;
}

注：mtk平台重感accel框架和光距感的alsps框架流程是类似的，想要分析重感accel框架可以在kernel-4.4/drivers/misc/mediatek/sensors-1.0/accelerometer/accel.c浏览；