diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/libcamera/control_serializer.cpp | 63 |
1 files changed, 58 insertions, 5 deletions
diff --git a/src/libcamera/control_serializer.cpp b/src/libcamera/control_serializer.cpp index e1ba6d14..77b77448 100644 --- a/src/libcamera/control_serializer.cpp +++ b/src/libcamera/control_serializer.cpp @@ -62,6 +62,14 @@ LOG_DEFINE_CATEGORY(Serializer) * corresponding ControlInfoMap handle in the binary data, and when * deserializing to retrieve the corresponding ControlInfoMap. * + * As independent ControlSerializer instances are used on both sides of the IPC + * boundary, and the two instances operate without a shared point of control, + * there is a potential risk of collision of the numerical handles assigned to + * each serialized ControlInfoMap. For this reason the control serializer is + * initialized with a seed and the handle is incremented by 2, so that instances + * initialized with a different seed operate on a separate numerical space, + * avoiding any collision risk. + * * In order to perform those tasks, the serializer keeps an internal state that * needs to be properly populated. This mechanism requires the ControlInfoMap * corresponding to a ControlList to have been serialized or deserialized @@ -77,9 +85,45 @@ LOG_DEFINE_CATEGORY(Serializer) * proceed with care to avoid stale references. */ -ControlSerializer::ControlSerializer() - : serial_(0) +/** + * \enum ControlSerializer::Role + * \brief Define the role of the IPC component using the control serializer + * + * The role of the component that creates the serializer is used to initialize + * the handles numerical space. + * + * \var ControlSerializer::Role::Proxy + * \brief The control serializer is used by the IPC Proxy classes + * + * \var ControlSerializer::Role::Worker + * \brief The control serializer is used by the IPC ProxyWorker classes + */ + +/** + * \brief Construct a new ControlSerializer + * \param[in] role The role of the IPC component using the serializer + */ +ControlSerializer::ControlSerializer(Role role) { + /* + * Initialize the handle numerical space using the role of the + * component that created the instance. + * + * Instances initialized for a different role will use a different + * numerical handle space, avoiding any collision risk when, in example, + * two instances of the ControlSerializer class are used at the IPC + * boundaries. + * + * Start counting handles from '1' as '0' is a special value used as + * place holder when serializing lists that do not have a ControlInfoMap + * associated (in example list of libcamera controls::controls). + * + * \todo This is a temporary hack and should probably be better + * engineered, but for the time being it avoids collisions on the handle + * value when using IPC. + */ + serialSeed_ = role == Role::Proxy ? 1 : 2; + serial_ = serialSeed_; } /** @@ -90,7 +134,7 @@ ControlSerializer::ControlSerializer() */ void ControlSerializer::reset() { - serial_ = 0; + serial_ = serialSeed_; infoMapHandles_.clear(); infoMaps_.clear(); @@ -200,10 +244,10 @@ int ControlSerializer::serialize(const ControlInfoMap &infoMap, else idMapType = IPA_CONTROL_ID_MAP_V4L2; - /* Prepare the packet header, assign a handle to the ControlInfoMap. */ + /* Prepare the packet header. */ struct ipa_controls_header hdr; hdr.version = IPA_CONTROLS_FORMAT_VERSION; - hdr.handle = ++serial_; + hdr.handle = serial_; hdr.entries = infoMap.size(); hdr.size = sizeof(hdr) + entriesSize + valuesSize; hdr.data_offset = sizeof(hdr) + entriesSize; @@ -212,6 +256,15 @@ int ControlSerializer::serialize(const ControlInfoMap &infoMap, buffer.write(&hdr); /* + * Increment the handle for the ControlInfoMap by 2 to keep the handles + * numerical space partitioned between instances initialized for a + * different role. + * + * \sa ControlSerializer::Role + */ + serial_ += 2; + + /* * Serialize all entries. * \todo Serialize the control name too */ |