HIDL SIMPLE

原文：https://devarea.com/android-hidl-and-project-treble/#.XLgyn7Ejw4A

One of the problems in Android is the fact that when a new version is released only a few devices can be updated. Actually, if you want to enjoy the latest version, you need to buy a new smartphone every 6 months. Google solution is the Project trebel that separates the vendor implementation from the Android OS framework via a new vendor interface

HIDL

HAL interface definition language used to describe the interface between the framework and the vendor. All hardware interfaces are located in hardware/interfaces in .hal files

Let’s go over simple example

Create all the path

1 2	# cd ~/aosp # mkdir -p hardware/interfaces/simple/2.0/default

Create a hal file in ISimphw.hal in hardware/interfaces/simple/2.0

package [email protected];

interface ISimphw {

simpfn(int32_t valueIn) generates (int32_t valueRet);

};

Generate the HAL files

To generate the HAL files you need to use the hidl-gen tool run:

# [email protected]

# LOC=hardware/interfaces/simple/2.0/default/

# make hidl-gen -j64

# hidl-gen -o $LOC -Lc++-impl -randroid.hardware:hardware/interfaces -randroid.hidl:system/libhidl/transport $PACKAGE

# hidl-gen -o $LOC -Landroidbp-impl -randroid.hardware:hardware/interfaces -randroid.hidl:system/libhidl/transport $PACKAGE

And to update all makefile (Android.mk, Android.bp) run:

1	# ./hardware/interfaces/update-makefiles.sh

Now add 2 empty files to hardware/interfaces/simple/2.0/default:

[email protected]
service.cpp

Now the directory hardware/interfaces/simple should look like this:

HIDL SIMPLE

Implementing the HAL shared object:

we need to add a new static function to return the service object (usually as a singleton)

Simphw.h

#ifndef ANDROID_HARDWARE_SIMPLE_V2_0_SIMPHW_H

#define ANDROID_HARDWARE_SIMPLE_V2_0_SIMPHW_H

#include <android/hardware/simple/2.0/ISimphw.h>

#include <hidl/MQDescriptor.h>

#include <hidl/Status.h>

namespace android {

namespace hardware {

namespace simple {

namespace V2_0 {

namespace implementation {

using ::android::hardware::hidl_array;

using ::android::hardware::hidl_memory;

using ::android::hardware::hidl_string;

using ::android::hardware::hidl_vec;

using ::android::hardware::Return;

using ::android::hardware::Void;

using ::android::sp;

struct Simphw : public ISimphw {

// Methods from ISimphw follow.

Return<int32_t> simpfn(int32_t valueIn) override;

// Methods from ::android::hidl::base::V1_0::IBase follow.

static ISimphw* getInstance(void);

};

// FIXME: most likely delete, this is only for passthrough implementations

//extern "C" ISimphw* HIDL_FETCH_ISimphw(const char* name);

} // namespace implementation

} // namespace V2_0

} // namespace simple

} // namespace hardware

} // namespace android

#endif // ANDROID_HARDWARE_SIMPLE_V2_0_SIMPHW_H

Simphw.cpp

#include "Simphw.h"

namespace android {

namespace hardware {

namespace simple {

namespace V2_0 {

namespace implementation {

// Methods from ISimphw follow.

Return<int32_t> Simphw::simpfn(int32_t valueIn) {

// TODO implement

return valueIn+100;

}

ISimphw *Simphw::getInstance(void){

return new Simphw();

}

// Methods from ::android::hidl::base::V1_0::IBase follow.

//ISimphw* HIDL_FETCH_ISimphw(const char* /* name */) {

// return new Simphw();

//}

} // namespace implementation

} // namespace V2_0

} // namespace simple

} // namespace hardware

} // namespace android

Note that if you want to support pass-through mode, you need to uncomment the HIDL_FETCH_ISimphw function

In this example, we implemented the function as simple as possible (usually we will load the hardware module here)

The generated Android.bp file build a shared library with the implementation – [email protected]

Creating the Service

To host the library we need to create a simple executable:

service.cpp

#define LOG_TAG "[email protected]"

#include <android/hardware/simple/2.0/ISimphw.h>

#include <hidl/LegacySupport.h>

#include "Simphw.h"

using android::hardware::simple::V2_0::ISimphw;

using android::hardware::simple::V2_0::implementation::Simphw;

using android::hardware::configureRpcThreadpool;

using android::hardware::joinRpcThreadpool;

using android::sp;

int main() {

int res;

android::sp<ISimphw> ser = Simphw::getInstance();

ALOGE("simp main");

configureRpcThreadpool(1, true /*callerWillJoin*/);

if (ser != nullptr) {

res = ser->registerAsService();

if(res != 0)

ALOGE("Can't register instance of SimpleHardware, nullptr");

} else {

ALOGE("Can't create instance of SimpleHardware, nullptr");

}

joinRpcThreadpool();

return 0; // should never get here

}

We create an instance of our implementation, Create a thread pool for the binder and register the current process as a service

Note that the function regsiterAsService() is auto-generated by hidl-gen tool

To make this service run automatically add init file:

[email protected]

service simphwserv /vendor/bin/hw/[email protected]

class hal

user root

group root

seclabel u:r:su:s0

For testing purpose I set the security label to su , we need to set SE Linux rules (I wrote it in the init.te file):

1 2	allow init vendor_file:file { execute }; allow init su:process { transition };

To tell the build system to build the service add the following to Android.bp (in directory default)

cc_binary {

name: "[email protected]",

defaults: ["hidl_defaults"],

proprietary: true,

relative_install_path: "hw",

srcs: ["service.cpp"],

init_rc: ["[email protected]"],

shared_libs: [

"[email protected]",

"libhidlbase",

"libhidltransport",

"liblog",

"libutils",

}

Add the following components to build/make/target/product/emulator.mk

1 2	[email protected] \ [email protected] \

Now build the ROM and run it, connect with adb and run ps -A to see all the hardware services:

HIDL SIMPLE

The lshal tool list all the hardware services by categories:

# lshal

HIDL SIMPLE

Writing the Client

To use the service we will write a simple client application. Usually, it will be part of the Android framework written by Google. For example, if the generic framework wants to access the vibrator service:

In file frameworks/base/services/core/jni/com_android_server_VibratorService.cpp

static sp<IVibrator> mHal;

...

mHal = IVibrator::getService();

...

Status retStatus = mHal->on(timeout_ms);

...

Status retStatus = mHal->off();

Add a new directory in device/generic/goldfish – simphaltest

Add the source and Android.bp files:

#define LOG_TAG "[email protected]"

#include <android/hardware/simple/2.0/ISimphw.h>

#include <hidl/Status.h>

#include <hidl/LegacySupport.h>

#include <utils/misc.h>

#include <utils/Log.h>

#include <hardware/hardware.h>

#include <hidl/HidlSupport.h>

#include<stdio.h>

using android::hardware::simple::V2_0::ISimphw;

using android::sp;

int main() {

int res;

android::sp<ISimphw> ser = ISimphw::getService();

res = ser->simpfn(200);

printf("val=%d\n",res);

return 0;

}

Android.bp

cc_binary {

name: "mysimptest",

defaults: ["hidl_defaults"],

proprietary: true,

srcs: ["servtest.cpp"],

shared_libs: [

"[email protected]",

"libhidlbase",

"libhidltransport",

"liblog",

"libutils",

}

Add the client test to build/make/target/product/emulator.mk

1	mysimptest \

Add hal entry to the Manifest.xml file of your device (device/generic/goldfish/Manifest.xml in this case)

<name>android.hardware.simple</name>

<transport>hwbinder</transport>

<name>ISimphw</name>

<instance>default</instance>

</interface>

</hal>

Build the ROM again and test our service:

HIDL SIMPLE

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33 THOUGHTS ON “ANDROID HIDL AND PROJECT TREBLE”

CHRIS_CW

This is the best DEMONSTRATION of How to get a HAL going I have found, Unfortunately When following it through on OREO my service fails to load the impl library from the ‘HW’ dir, if I push the library up a level to the lib64, it is found. I see nearly all the other standard(or BSP) HALS are lOAded from ‘HW’ but I cant see what they have different. Whats the trick ?
I get:
“library “[email protected]” not found”
Although it is clearly there and it does load if I move it up to lib64
MARCH 21, 2018
- REPLY
1. KEN
  
  Hello,
  HAVE you FIGURED OUT WHY THIS IS HAPPENING? I AM CURRENTLY HAVING THIS ISSUE. PLEASE LET ME KNOW IF YOU FIND ANY SOLUTION.
  THANKS
  MAY 25, 2018
  - REPLY
  1. JIHYUN
    
    hi
    
    i also have this problem.
    a simple way to avoid it, just copy so file to /system/lib. then it’s gone.
    but it seems not a good way. if anyone knows it.
    please share.
    JUNE 25, 2018
    - REPLY
    1. JIHYUN
      
      Hi I resolved it by avoding linking *-impl.so file.
      I removed getInstance method and added below method
      
      ISimphw* HIDL_FETCH_ISimphw(const char* /* name */) {
      return new Simphw();
      }
      and modified service.cpp as below.
      
      int main() {
      return defaultPassthroughServiceImplementation();
      }
      maybe linking *-impl.so in /vendor/lib/hw is not allowed.
      instead, I’m guessing that it’s automatically loaded by using HIDL_FETCH_ISIMPHW.
      JUNE 25, 2018
      - REPLY
      1. RAJU KHANAL
        
        @JIHYUN: I followed your steps but still get the following error.
        hwservicemanager: getTransport: Cannot find entry [email protected]::ISimphw/default in either framework or device manifest.
        10-18 01:06:20.990 1577 1577 E ServiceManagement: Passthrough lookup opened [email protected] but could not find symbol HIDL_FETCH_ISimphw: undefined symbol: HIDL_FETCH_ISimphw
        10-18 01:06:20.990 1577 1577 E [email protected]: Could not get passthrough implementation for [email protected]::ISimphw/default.
        
        I do the the hidl fetch method but don’t know why it is coming this way. Any suggestions? I have been stuck in this.
        OCTOBER 17, 2018
        -
      2. RAJU KHANAL
        
        Please note the error is not with the naming convention.
        So the proper error would be:
        @JIHYUN: I followed your steps but still get the following error.
        hwservicemanager: getTransport: Cannot find entry [email protected]::ISimphw/default in either framework or device manifest.
        10-18 01:06:20.990 1577 1577 E ServiceManagement: Passthrough lookup opened [email protected] but could not find symbol HIDL_FETCH_ISimphw: undefined symbol: HIDL_FETCH_ISimphw
        10-18 01:06:20.990 1577 1577 E [email protected]: Could not get passthrough implementation for [email protected]::ISimphw/default.
        
        Kindly ignore the part where the name is [email protected] I have the correct impl file name.
        OCTOBER 17, 2018
        -
PHONG

What IDE to run the code?
MARCH 26, 2018
- REPLY
RAKESH VERMA

thanks a lot, works great. Required to update dev/*/* in Android.bp in root directory to dev/*/*/* to access the Android.bp created in device/generic/goldfish/simphaltest.
MARCH 27, 2018
- REPLY
AJINATH

hI,

I tried steps given for “[email protected]″ HIDL interface and thats worked. I like the simple steps/command to generate HIDL impl and HIDL service, it really gives the confidence for who are new into Android HAL framework.

Thanks a lot.

One more change is required to build HIDL impl lib, just add “2.0/default” into Android.bp to include default dir Android.bp

hardware/interfaces/simple/Android.bp

subdirs = [
“2.0”,
“2.0/default”,
]

@CHRIS_CW,

As per hardware/interfaces/simple/2.0/default/Android.bp rule,

name: “[email protected]”,
relative_install_path: “hw”,
proprietary: true,

the impl lib should build at below location in vendor.img

vendor/lib/hw
vendor/lib64/hw

can check your HIDL package name ? from error it seems to be UPPER case string issue “library “[email protected]” not found”
”

and also check product packages should include in devicexx.mk

PRODUCT_PACKAGES += \
[email protected] \
[email protected] \
APRIL 9, 2018
- REPLY
1STPIE

it so good refference. thanks
APRIL 19, 2018
- REPLY
AARTI

Hi
I followed the steps given above but i am getting following error while trying to generate the HIDL files:

ERROR: Unable to automatically import ‘[email protected]::IBase’ at /home/AOSP/hardware/interfaces/simple/2.0/ISimple.hal
ERROR: Could not parse [email protected]::ISimple Aborting
APRIL 20, 2018
- REPLY
1STPIE

hello.
i have a question.
i dont make android.mk files about simple directory.
i try to execute hardware/interfaces/update-makefiels.sh
and i got a message about this.
Updating [email protected]

but in the directory of simple/2.0/
dont find a android.mk file.
APRIL 24, 2018
- REPLY
ANONYMOUS

In service.cpp, should “return 1” “if(res != 0)”, else would “joinRpcThreadpool();” without a registered instance of SimpleHardware.

P/S: Sorry about all caps. something wrong somewhere i can’t type in lowercase.
MAY 11, 2018
- REPLY
ANONYMOUS

Also need “return 1” “if(ser == nullptr)”.
MAY 11, 2018
- REPLY
ANONYMOUS

@Rakesh Verma
How did you get “hidl-gen” and “update-makefiles.sh” to detect your *.hal files if you put your source code under device/generic/goldfish/simphaltest? or did you generate everything under hardware/interfaces and moved them to device/generic/goldfish/simphaltest later?
MAY 13, 2018
- REPLY
1. LIRAN B.H
  
  update-makefiles.sh only generates the makefiles under hardware/interfaces
  follow the instructions and create the testapp makefile manually
  MAY 13, 2018
  - REPLY
  1. ANONYMOUS
    
    Thanks! IS THERE A WAY TO IMPLEMENT A BOARD/TARGET SPECIFIC VERSION OF THIS AND ‘OVERWRITE’ (OR NOT USE) THE DEFAULT IMPLEMENTATION? E.g. using device/generic/marlin/SIMPLE rather than hardware/interfaces/SIMPLE? As you’d mentioned, update-makefiles.sh doesn’t seem to detect *.hal files under devices/*, so this has to be done manually, but how should the terms [email protected] and [email protected] AND [email protected] be renamed for the BOARD/TARGET? Thanks in advance.
    MAY 17, 2018
    - REPLY
    1. ANONYMOUS
      
      Sorry again for caps!
      MAY 17, 2018
      - REPLY
2. RATNESH PAL
  
  Hope you resolved your error, I follow the same instruction everything is working fine but try to run test code getting error. I could not understand the mean so please help me,
  My test code path is here aosp8/device/generic/goldfish/mysimptest.
  127|generic_x86:/ $ mysimptest/
  mysimptest/
  /system/bin/sh: mysimptest/: not found
  127|generic_x86:/ $
  APRIL 13, 2019
  - REPLY
RAJIV RANJAN

superb link till now.
MAY 16, 2018
- REPLY
SAI PHANI TEJA SREERAM

The best tutorial of hidl so far got in the internet. Thanks
JULY 17, 2018
- REPLY
DEEPTIMAN PATTNAIK

it’s a great tutorial to get started with HIDL implementation.

I am just facing an issue, while build the hidl modules.

ERROR: Could not open package path hardware/interfaces/simple/2.0/ for package [email protected]:
AUGUST 1, 2018
- REPLY
BRIAN

Hi All,

I am trying to implement an I2C DAC in android to allow the driving of specific voltages from an app. This isn’t a DAC for audio etc, it is an embedded application. I will also be implementing ADC, GPIO etc.

I have found a kernel driver for the specific DAC I am using, and can control the DAC via the sysfs interface, e.g. “echo 3000 > /sys/bus/iio/devices/iio:device0/out_voltage0_raw”

Now I am trying to understand how HIDL, HAL etc fit in to this.

– I have found an example (https://elinux.org/images/f/fb/Android_Customization-_From_the_Kernel_to_the_Apps.pdf) which seems to create a custom service to control a hardware device, however this edits some of the internal files in android to start the service etc, and therefore I think this is NOT the “Andriod Oreo” way of doing it, since these modifications will be wiped during an upgrade.

– Other examples I have found seem to be for sensor implementation. Since the DAC is an output, I don’t think the sensor API is compatible with what I am trying to achieve.

As I understand it, Android Oreo 8.0 introduced the treble concept to allow the operating system to be updated while keeping the vendor specific changes intact. Am I correct in saying that this example is compatible with communicating with a custom device? e.g. instead of doing “return valueIn+100;”, I could “open(DEV, O_WRONLY);” etc and interface with my device?
AUGUST 6, 2018
- REPLY
BRIAN

Does anyone know how I would call the function from within an Android App using Android Studio? I have generated an SDK after implementing this but I don’t know what Java API is exposed, if any?
AUGUST 7, 2018
- REPLY
ANIL KUMAR

I am not able to send data to another shared library from my HIDL server, I am sending some data form client to server, from server i am trying to send to another library which is normal C implementation, i am able to call but data is not reaching. Can you please help.
AUGUST 16, 2018
- REPLY
YUZHOU

Hi,
Thanks for the detailed documentation. A question regarding the init_rc file and SELinux init.te rule. As you mentioned:

FOR TESTING PURPOSE I SET THE SECURITY LABEL TO SU , WE NEED TO SET SE LINUX RULES (I WROTE IT IN THE INIT.TE FILE):
ALLOW INIT VENDOR_FILE:FILE { EXECUTE };
ALLOW INIT SU:PROCESS { TRANSITION };

Could you please clarify what should be the setting for normal use case? I have tried to copy the init_rc file from audio, omx HAL and the service won’t load up unless I use your sepolicy here. Is there a formal way to tell the system to load up the hal service while booting?
AUGUST 28, 2018
- REPLY
WANG ZHIKAI

hi
as you said “we need to set SE Linux rules (I wrote it in the init.te file):”
i don’t know which init.te file should config, could you tell me the location of init.te file?
thank you very much!
SEPTEMBER 12, 2018
- REPLY
RAJU KHANAL

When I do an lshal I can see that it is getting generated as passthrough and not binderized

All available passthrough implementations (all -impl.so files).
These may return subclasses through their respective HIDL_FETCH_I* functions.
R Interface
[email protected]::I*/* (/vendor/lib/hw/)

Should I not get this in the category binderized as default and looking something like what you have shown in the figure:
[email protected]::ISimphw/default

What I am missing here if anyone can help?
Sorry for the capslock. i could not change the case
OCTOBER 16, 2018
- REPLY
1. RAJU KHANAL
  
  Also i cannot see the same in ls -a. However I can see the so file in system/lib and in lshal as above.
  OCTOBER 16, 2018
  - REPLY
ARINDAM

IMPORTANT :

I NEED to use an HIDL service( in CPP) while my client is in java (telephony fw).

I need to register call backs in the service from my java module, so that i can receive notifications in telephony when there is an update in the c++ service.

thanks
DECEMBER 27, 2018
- REPLY
ANONYMOUS

Nice post
MARCH 27, 2019
- REPLY
RATNESH

Hi,
Thank you very much for nice tutorial, I am stuck in init.te file.
Can you please tell me location of init.te file so i will set the given rules.
allow init vendor_file:file { execute };
allow init su:process { transition };
Waiting for your response!
APRIL 4, 2019
- REPLY
RATNESH

After Adding
allow init vendor_file:file { execute };
allow init su:process { transition };
at bottom of /system/sepolicy/public/init.te
…………………………………………….
PRODUCT_PACKAGES += \
[email protected] \
[email protected] \
and also added emualtor.mk

after build rom getting this error

[email protected]:~/android8$ make -j4
============================================
PLATFORM_VERSION_CODENAME=REL
PLATFORM_VERSION=8.1.0
TARGET_PRODUCT=aosp_x86_64
TARGET_BUILD_VARIANT=eng
TARGET_BUILD_TYPE=release
TARGET_ARCH=x86_64
TARGET_ARCH_VARIANT=x86_64
TARGET_2ND_ARCH=x86
TARGET_2ND_ARCH_VARIANT=x86_64
HOST_ARCH=x86_64
HOST_2ND_ARCH=x86
HOST_OS=linux
HOST_OS_EXTRA=Linux-4.18.0-16-generic-x86_64-with-Ubuntu-18.04-bionic
HOST_CROSS_OS=windows
HOST_CROSS_ARCH=x86
HOST_CROSS_2ND_ARCH=x86_64
HOST_BUILD_TYPE=release
BUILD_ID=OPM7.181205.001
OUT_DIR=out
============================================
[2/2] bootstrap out/soong/.minibootstrap/build.ninja.in
[1/1] out/soong/.bootstrap/bin/minibp out/soong/.bootstrap/build.ninja
[78/79] glob hardware/interfaces/wifi/1.1/Android.bp
[4/4] out/soong/.bootstrap/bin/soong_build out/soong/build.ninja
FAILED: out/soong/build.ninja
out/soong/.bootstrap/bin/soong_build -t -b out/soong -d out/soong/build.ninja.d -o out/soong/build.ninja Android.bp
error: hardware/interfaces/simple/2.0/default/Android.bp:1:1: “[email protected]” depends on undefined module “[email protected]”
ninja: build stopped: subcommand failed.
23:45:48 soong failed with: exit status 1
APRIL 4, 2019
- REPLY

HIDL

Generate the HAL files

Implementing the HAL shared object:

Creating the Service

Writing the Client

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33 THOUGHTS ON “ANDROID HIDL AND PROJECT TREBLE”

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