[libcamera-devel] [PATCH v2 3/4] android: camera_hal_manager: Support camera hotplug
Kieran Bingham
kieran.bingham at ideasonboard.com
Fri Aug 14 10:45:58 CEST 2020
Hi Umang,
On 14/08/2020 09:29, Umang Jain wrote:
> Hi Niklas,
>
> On 8/13/20 5:52 PM, Umang Jain wrote:
>> Hi Niklas
>>
>> On 8/13/20 5:14 PM, Niklas Söderlund wrote:
>>> Hi Umang,
>>>
>>> Thanks for your work.
>>>
>>> On 2020-08-10 12:04:14 +0000, Umang Jain wrote:
>>>> Extend the support for camera hotplug from libcamera's CameraManager
>>>> to CameraHalManager. Use camera module callbacks to let the framework
>>>> know about the hotplug events and change the status of cameras being
>>>> being hotplugged or unplugged via camera_device_status_change().
>>>>
>>>> Introduce a map camerasMap_ which book-keeps all cameras seen in the
>>>> past by the CameraHalManager. If the camera is seen for the first time,
>>>> a new id is assigned to it. If the camera has been seen before by the
>>>> manager, it's old id is reused. IDs for internal cameras start with
>>>> '0' and for external cameras, they start with '1000'. Note, for the
>>>> current implementation, we assume all UVC cameras are external cameras.
>>> I wonder if keeping the cache of previously seen cameras or if we should
>>> not just treat any hot-plugged camera as a new one? I can't think of any
>>> benefit of preserving the same numerical ID between two plug events,
>>> while I can think of quiet a few cons.
>>>
>>> - It's confusing when debugging as un-plugging and then replugging the
>>> same camera will result in logs where the numerical ID is the same
>>> for
>>> both. This may even result in things working by "chance" is it reuses
>>> an already known numerical ID.
>>>
>>> - Looking at the code plugging a UVC camera in a different USB port will
>>> generate a different Camera::id() result and then be treated as a new
>>> camera vs plugging it in the same port and it then being treatad as a
>>> new camera.
>> Ah, I just noticed this point. I assumed each camera will generate it's
>> own unique ID, plugged in for any of the ports. I am not sure, what
>> actions/
>> measure we can take here to address this.
The 'same' camera plugged into a different USB port will be treated as a
new camera. I don't think we can do anything to prevent that.
There is as far as I know, no way to uniquely identify an externally
connected camera. Nothing is trusted, as serial numbers are rarely set
uniquely and there is no specification on UVC to have any unique identifier.
Therefore, I think matching to the unique ID we have from libcamera is
the best thing we can do at this layer.
That leaves any decision as to how to identify a camera to libcamera,
not the android layer.
>>>
>>> - The logic in this patch is more complex due to it both having to deal
>>> with known and new cameras.
>>>
>>> What is the benefit of this cache that I'm missing?
>> Laurent is following up too here, so I'll wait.
>> I basically took his suggestion from the v1 review [1] and steered the
>> patch into that
>> direction.
>>
>>>
>>>> CameraDevice is now a shared object and cameras_ vector stores shared
>>>> pointers to CameraDevice. This is done in order to introduce reference
>>>> counting for CameraDevice objects - especially to handle hot-unplug
>>>> events. Both camerasMap_ and cameras_ are protected by a mutex.
>>>>
>>>> Signed-off-by: Umang Jain <email at uajain.com>
>>>> ---
>>>> src/android/camera_device.cpp | 15 +++
>>>> src/android/camera_device.h | 8 +-
>>>> src/android/camera_hal_manager.cpp | 153
>>>> ++++++++++++++++++++++++-----
>>>> src/android/camera_hal_manager.h | 15 ++-
>>>> 4 files changed, 166 insertions(+), 25 deletions(-)
>>>>
>>>> diff --git a/src/android/camera_device.cpp
>>>> b/src/android/camera_device.cpp
>>>> index d918350..a79bb69 100644
>>>> --- a/src/android/camera_device.cpp
>>>> +++ b/src/android/camera_device.cpp
>>>> @@ -233,6 +233,21 @@ CameraDevice::~CameraDevice()
>>>> delete it.second;
>>>> }
>>>> +std::shared_ptr<CameraDevice> CameraDevice::create(unsigned int id,
>>>> + const std::shared_ptr<Camera> &cam)
>>>> +{
>>>> + struct Deleter : std::default_delete<CameraDevice> {
>>>> + void operator()(CameraDevice *camera)
>>>> + {
>>>> + delete camera;
>>>> + }
>>>> + };
>>>> +
>>>> + CameraDevice *camera = new CameraDevice(id, cam);
>>>> +
>>>> + return std::shared_ptr<CameraDevice>(camera, Deleter());
>>>> +}
>>> As Kieran points out I think this should be added in a separate as this
>>> one is quiet large and therefore hard to review.
>>>
>>>> +
>>>> /*
>>>> * Initialize the camera static information.
>>>> * This method is called before the camera device is opened.
>>>> diff --git a/src/android/camera_device.h b/src/android/camera_device.h
>>>> index 7be9e11..7f9e010 100644
>>>> --- a/src/android/camera_device.h
>>>> +++ b/src/android/camera_device.h
>>>> @@ -47,8 +47,8 @@ struct CameraStream {
>>>> class CameraDevice : protected libcamera::Loggable
>>>> {
>>>> public:
>>>> - CameraDevice(unsigned int id, const
>>>> std::shared_ptr<libcamera::Camera> &camera);
>>>> - ~CameraDevice();
>>>> + static std::shared_ptr<CameraDevice> create(unsigned int id,
>>>> + const
>>>> std::shared_ptr<libcamera::Camera> &cam);
>>>> int initialize();
>>>> @@ -57,6 +57,7 @@ public:
>>>> unsigned int id() const { return id_; }
>>>> camera3_device_t *camera3Device() { return &camera3Device_; }
>>>> + const libcamera::Camera *getCamera() { return camera_.get(); };
>>> Same here this can be done in a separate commit. Also I think this could
>>> be named camera() instead of getCamera()
>> Noted. Well, this would then be a single-line patch and we won't be
>> able to see where
>> it's used. I am under the impression that API introduction and it's
>> relevant usage should
>> be done in a single commit(this patch uses the ->getCamera()) so ....
>> one can the entire
>> picture of the diff change.
As it's a single line addition, this can be in the patch that adds it, I
think the aim is just to try to simplify the changes in this patch a bit
- as there are quite a few things going on so it's harder to parse.
>>>
>>>> int facing() const { return facing_; }
>>>> int orientation() const { return orientation_; }
>>>> @@ -72,6 +73,9 @@ protected:
>>>> std::string logPrefix() const override;
>>>> private:
>>>> + CameraDevice(unsigned int id, const
>>>> std::shared_ptr<libcamera::Camera> &camera);
>>>> + ~CameraDevice();
>>>> +
>>>> struct Camera3RequestDescriptor {
>>>> Camera3RequestDescriptor(unsigned int frameNumber,
>>>> unsigned int numBuffers);
>>>> diff --git a/src/android/camera_hal_manager.cpp
>>>> b/src/android/camera_hal_manager.cpp
>>>> index 3d6d2b4..fdde2c0 100644
>>>> --- a/src/android/camera_hal_manager.cpp
>>>> +++ b/src/android/camera_hal_manager.cpp
>>>> @@ -8,6 +8,7 @@
>>>> #include "camera_hal_manager.h"
>>>> #include <libcamera/camera.h>
>>>> +#include <libcamera/property_ids.h>
>>>> #include "libcamera/internal/log.h"
>>>> @@ -35,6 +36,7 @@ CameraHalManager::CameraHalManager()
>>>> CameraHalManager::~CameraHalManager()
>>>> {
>>>> cameras_.clear();
>>>> + camerasMap_.clear();
>>>> if (cameraManager_) {
>>>> cameraManager_->stop();
>>>> @@ -47,6 +49,13 @@ int CameraHalManager::init()
>>>> {
>>>> cameraManager_ = new CameraManager();
>>>> + /* Support camera hotplug. */
>>>> + cameraManager_->cameraAdded.connect(this,
>>>> &CameraHalManager::cameraAdded);
>>>> + cameraManager_->cameraRemoved.connect(this,
>>>> &CameraHalManager::cameraRemoved);
>>>> +
>>>> + cameraCounter_ = 0;
>>>> + externalCameraCounter_ = 1000;
>>>> +
>>>> int ret = cameraManager_->start();
>>>> if (ret) {
>>>> LOG(HAL, Error) << "Failed to start camera manager: "
>>>> @@ -56,35 +65,25 @@ int CameraHalManager::init()
>>>> return ret;
>>>> }
>>>> - /*
>>>> - * For each Camera registered in the system, a CameraDevice
>>>> - * gets created here to wraps a libcamera Camera instance.
>>>> - *
>>>> - * \todo Support camera hotplug.
>>>> - */
>>>> - unsigned int index = 0;
>>>> - for (auto &cam : cameraManager_->cameras()) {
>>>> - CameraDevice *camera = new CameraDevice(index, cam);
>>>> - ret = camera->initialize();
>>>> - if (ret)
>>>> - continue;
>>>> -
>>>> - cameras_.emplace_back(camera);
>>>> - ++index;
>>>> - }
>>>> -
>>>> return 0;
>>>> }
>>>> CameraDevice *CameraHalManager::open(unsigned int id,
>>>> const hw_module_t *hardwareModule)
>>>> {
>>>> - if (id >= numCameras()) {
>>>> + MutexLocker locker(mutex_);
>>>> +
>>>> + auto iter = std::find_if(cameras_.begin(), cameras_.end(),
>>>> + [id](std::shared_ptr<CameraDevice> &cam) {
>>>> + return cam->id() == id;
>>>> + });
>>>> + if (iter == cameras_.end()) {
>>> I think you should break this (and the similar ones below) into private
>>> helpers instead if implementing the logic in-place
>>>
>>> CameraHalManager::cameraFromAndroidId(..);
>>> CameraHalManager::androidIdFromCamera(..);
>>>> LOG(HAL, Error) << "Invalid camera id '" << id << "'";
>>>> return nullptr;
>>>> }
>>>> - CameraDevice *camera = cameras_[id].get();
>>>> + CameraDevice *camera = iter->get();
>>>> +
>>>> if (camera->open(hardwareModule))
>>>> return nullptr;
>>>> @@ -93,9 +92,91 @@ CameraDevice *CameraHalManager::open(unsigned
>>>> int id,
>>>> return camera;
>>>> }
>>>> +void CameraHalManager::cameraAdded(std::shared_ptr<Camera> cam)
>>>> +{
>>>> + unsigned int id;
>>>> + bool isCameraExternal = false;
>>>> + bool isCameraNew = false;
>>>> +
>>>> + MutexLocker locker(mutex_);
>>>> +
>>>> + /* Each camera is assigned a unique integer id when it is seen
>>>> for the
>>>> + * first time. If the camera has been seen before, the id is
>>>> reused and
>>>> + * the camera is marked as CAMERA_DEVICE_STATUS_PRESENT
>>>> subsequently.
>>>> + *
>>>> + * ID starts from '0' for internal cameras and '1000' for
>>>> external cameras.
>>>> + */
>>>> + auto iter = camerasMap_.find(cam->id());
>>>> + if (iter != camerasMap_.end()) {
>>>> + id = iter->second;
>>>> + } else {
>>>> + isCameraNew = true;
>>>> +
>>>> + /*
>>>> + * Now check if this is an external camera and assign
>>>> + * its id accordingly.
Only for consistency, there's a double space indent on the text here,
rather than single used everywhere else.
>>>> + */
>>>> + const ControlList &properties = cam->properties();
>>>> + if (properties.contains(properties::Location) &&
>>>> + properties.get(properties::Location) &
>>>> + properties::CameraLocationExternal) {
>>>> + isCameraExternal = true;
>>>> + id = externalCameraCounter_;
>>>> + } else {
>>>> + id = cameraCounter_;
>>>> + }
>>> As I understand it the information the HAL wants is whether or not the
>>> camera can be hot-plugged (id >= 1000) or nor (id < 1000)?
>> Again, the spec is not clear on the hot-plugged / removable camera IDs
>> front.
>> It is though clear on the internal cameras IDs - should start from 0,
>> hence,
>> we thought 1000 is a good number for assigning IDs for external cameras.
>>>
>>> If so I wonder if using the camera location as a judgment of the camera
>>> is hot-plugged or not is the way to go here? Imagine a device where the
>>> camera is permanently attached (not hot-unpluggable) but not fixated in
>>> a location. I'm thinking cameras mounted at the end of instruments
>>> (medical instruments, hand held tools) or robotics (mounted at the arm
>>> of a welding robot). I would imagine those cameras would be marked as
>>> located externally but they would not really be hot-pluggable.
>> Yes, I get your point. Their location is external, but from the
>> point-of-view
>> of HAL, they are still needed to be treated as "internal" cameras, no?
>> I guess, in HAL, internal cameras are the ones, which cannot be detached
>> from the device, whereas external cameras are the one, which can,
>> (Just a guess, I might be entirely wrong)
I think given that the android layer only makes the distinction of
'internal' or 'external', that's all we need to follow currently.
As seen in other mails, I too have thought they are two distinct states,
but alas ... I guess we just work to 'internal' and 'external' for now.
>>>
>>> I understand we have no other way to report or detect this at the moment
>>> and I'm not pushing hard for this to be solved as part of this series if
>>> it's not easy. But I think a bigger comment here is needed explaining
>>> that the HAL wants to know if a camera is hot-pluggable or not and does
>>> not really care if it's located internally or externally. I also think a
>>> \todo should be added so it's not forgotten.
>>>
>>>> + }
>>>> +
>>>> + /*
>>>> + * For each Camera registered in the system, a CameraDevice
>>>> + * gets created here to wraps a libcamera Camera instance.
>>>> + */
>>>> + std::shared_ptr<CameraDevice> camera = CameraDevice::create(id,
>>>> std::move(cam));
>>>> + int ret = camera->initialize();
>>>> + if (ret) {
>>>> + LOG(HAL, Error) << "Failed to initialize camera: " <<
>>>> cam->id();
>>>> + return;
>>>> + }
>>>> +
>>>> + if (isCameraNew) {
>>>> + camerasMap_.emplace(cam->id(), id);
>>>> +
>>>> + if (isCameraExternal)
>>>> + externalCameraCounter_++;
>>>> + else
>>>> + cameraCounter_++;
>>>> + }
>>>> +
>>>> + cameras_.emplace_back(std::move(camera));
>>>> +
>>>> + if (callbacks_)
>>>> + callbacks_->camera_device_status_change(callbacks_, id,
>>>> + CAMERA_DEVICE_STATUS_PRESENT);
>>>> + LOG(HAL, Debug) << "Camera ID: " << id << " added successfully.";
>>>> +}
>>>> +
>>>> +void CameraHalManager::cameraRemoved(std::shared_ptr<Camera> cam)
>>>> +{
>>>> + MutexLocker locker(mutex_);
>>>> +
>>>> + auto iter = std::find_if(cameras_.begin(), cameras_.end(),
>>>> + [cam](std::shared_ptr<CameraDevice> &camera) {
>>>> + return cam.get() == camera->getCamera();
>>>> + });
>>>> + if (iter == cameras_.end())
>>>> + return;
>>>> +
>>>> + unsigned int id = (*iter)->id();
>>>> + callbacks_->camera_device_status_change(callbacks_, id,
>>>> + CAMERA_DEVICE_STATUS_NOT_PRESENT);
>>>> + cameras_.erase(iter);
>>>> +
>>>> + LOG(HAL, Debug) << "Camera ID: " << id << " removed
>>>> successfully.";
>>>> +}
>>>> +
>>>> unsigned int CameraHalManager::numCameras() const
>>>> {
>>>> - return cameraManager_->cameras().size();
>>>> + return cameraCounter_;
>>>> }
>>>> int CameraHalManager::getCameraInfo(unsigned int id, struct
>>>> camera_info *info)
>>>> @@ -103,12 +184,18 @@ int CameraHalManager::getCameraInfo(unsigned
>>>> int id, struct camera_info *info)
>>>> if (!info)
>>>> return -EINVAL;
>>>> - if (id >= numCameras()) {
>>>> + MutexLocker locker(mutex_);
>>>> +
>>>> + auto iter = std::find_if(cameras_.begin(), cameras_.end(),
>>>> + [id](std::shared_ptr<CameraDevice> &cam) {
>>>> + return cam->id() == id;
>>>> + });
>>>> + if (iter == cameras_.end()) {
>>>> LOG(HAL, Error) << "Invalid camera id '" << id << "'";
>>>> return -EINVAL;
>>>> }
>>>> - CameraDevice *camera = cameras_[id].get();
>>>> + CameraDevice *camera = iter->get();
>>>> info->facing = camera->facing();
>>>> info->orientation = camera->orientation();
>>>> @@ -124,4 +211,26 @@ int CameraHalManager::getCameraInfo(unsigned
>>>> int id, struct camera_info *info)
>>>> void CameraHalManager::setCallbacks(const
>>>> camera_module_callbacks_t *callbacks)
>>>> {
>>>> callbacks_ = callbacks;
>>>> +
>>>> + MutexLocker locker(mutex_);
>>>> + /*
>>>> + * Few cameras might have been hotplugged before setting
>>>> callbacks_ here.
>>>> + * We need to mark CAMERA_DEVICE_STATUS_PRESENT for them
>>>> explicitly.
>>>> + * This hold only for external cameras, as internal cameras are
>>>> assumed to
>>>> + * be present at module load time, by the framework.
>>>> + */
>>>> + for (auto &cam : cameraManager_->cameras()) {
>>>> + auto iter = camerasMap_.find(cam->id());
>>>> + if (iter == camerasMap_.end())
>>>> + continue;
>>>> +
>>>> + unsigned int id = iter->second;
>>>> + const ControlList &properties = cam->properties();
>>>> + if (properties.contains(properties::Location) &&
>>>> + properties.get(properties::Location) &
>>>> + properties::CameraLocationExternal) {
>>>> + callbacks_->camera_device_status_change(callbacks_, id,
>>>> + CAMERA_DEVICE_STATUS_PRESENT);
>>>> + }
>>>> + }
>>>> }
>>>> diff --git a/src/android/camera_hal_manager.h
>>>> b/src/android/camera_hal_manager.h
>>>> index a582f04..7c481d4 100644
>>>> --- a/src/android/camera_hal_manager.h
>>>> +++ b/src/android/camera_hal_manager.h
>>>> @@ -7,6 +7,8 @@
>>>> #ifndef __ANDROID_CAMERA_MANAGER_H__
>>>> #define __ANDROID_CAMERA_MANAGER_H__
>>>> +#include <map>
>>>> +#include <mutex>
>>>> #include <stddef.h>
>>>> #include <vector>
>>>> @@ -18,6 +20,9 @@
>>>> class CameraDevice;
>>>> +using Mutex = std::mutex;
>>>> +using MutexLocker = std::unique_lock<std::mutex>;
>>>> +
>>>> class CameraHalManager
>>>> {
>>>> public:
>>>> @@ -33,10 +38,18 @@ public:
>>>> void setCallbacks(const camera_module_callbacks_t *callbacks);
>>>> private:
>>>> + void cameraAdded(std::shared_ptr<libcamera::Camera> cam);
>>>> + void cameraRemoved(std::shared_ptr<libcamera::Camera> cam);
>>>> +
>>>> libcamera::CameraManager *cameraManager_;
>>>> const camera_module_callbacks_t *callbacks_;
>>>> - std::vector<std::unique_ptr<CameraDevice>> cameras_;
>>>> + std::vector<std::shared_ptr<CameraDevice>> cameras_;
>>>> + std::map<std::string, unsigned int> camerasMap_;
>>> If each hot-plugged camera where treated as a new camera cameras_ and
>>> camerasMap_ could be merged to a
>>>
>>> std::map<unsigned int, std::shared_ptr<CameraDevice>> cameras_;
>>>
>>> Which would eliminate the possibility of them going out-of-sync.
>> Great point. I hope it's not too cubersome to iterate over all the
>> entires,
>> to find the exact CameraDevice we want for various plug events handler.
>> I will look into it.
> I found this to be a bit cubersome to implement. The foundation issue
> here is:
> we do need to cache the android HAL's ID<->libcamera::Camera::id mapping
> to identify if we are replugging an already-seen camera (I am assuming that
> libcamera::Camera::id is a unique ID generated by libcamera for each camera
> and is constant whenever the camera is replugged).
>
> If I just maintain a single map std::map<unsigned int,
> std::shared_ptr<CameraDevice>>
> the CameraDevice will be deleted on hot-unplug. Then I do not have a
> comparator to
> compare against, to know if the ID key should be reused or not, when
> hotplug event
> handlers.
Indeed, we can't map to something that would disappear, and we shouldn't
keep the CameraDevice around longer than necessary after it has been
unplugged.
I think a map of (android int) id to (unique string libcamera) id is
sufficient.
>>>
>>>> + Mutex mutex_;
>>>> +
>>>> + unsigned int externalCameraCounter_;
>>>> + unsigned int cameraCounter_;
>>>> };
>>>> #endif /* __ANDROID_CAMERA_MANAGER_H__ */
>>>> --
>>>> 2.26.2
>>>>
>>>> _______________________________________________
>>>> libcamera-devel mailing list
>>>> libcamera-devel at lists.libcamera.org
>>>> https://lists.libcamera.org/listinfo/libcamera-devel
>> [1] :
>> https://lists.libcamera.org/pipermail/libcamera-devel/2020-August/011857.html
>>
>> _______________________________________________
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>> libcamera-devel at lists.libcamera.org
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--
Regards
--
Kieran
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