drm_hwcomposer: Produce stable port IDs
Currently, port IDs are generated by returning a monotonically
increasing value (uint64_t hwc2_display_t). This is problematic for
two reasons:
hwc2_display_t is a 64bit value, and the returned port is 8bit.
clients of drm-hwc cannot rely on port ID consistency between
re-plugs to the same connector.
This patch provides a more stable approach to producing port IDs. We
combine the index of the DRM device in the device list, with the
index of the connector within a DRM device in a 3/5 bit split. This will
allow us to support up to 8 DRM devices, each with 32 independent
connectors (ports). If more support is required in the future, we will
have to extend the API to return uint16_t port values instead.
Signed-off-by: Gil Dekel <gildekel@google.com>
diff --git a/drm/DrmDevice.h b/drm/DrmDevice.h
index 7ee7d10..baa719d 100644
--- a/drm/DrmDevice.h
+++ b/drm/DrmDevice.h
@@ -37,13 +37,17 @@
public:
~DrmDevice() = default;
- static auto CreateInstance(std::string const &path, ResourceManager *res_man)
- -> std::unique_ptr<DrmDevice>;
+ static auto CreateInstance(std::string const &path, ResourceManager *res_man,
+ uint32_t index) -> std::unique_ptr<DrmDevice>;
auto &GetFd() const {
return fd_;
}
+ auto GetIndexInDevArray() const {
+ return index_in_dev_array_;
+ }
+
auto &GetResMan() {
return *res_man_;
}
@@ -103,12 +107,13 @@
DrmProperty *property) const;
private:
- explicit DrmDevice(ResourceManager *res_man);
+ explicit DrmDevice(ResourceManager *res_man, uint32_t index);
auto Init(const char *path) -> int;
static auto IsKMSDev(const char *path) -> bool;
SharedFd fd_;
+ const uint32_t index_in_dev_array_;
std::vector<std::unique_ptr<DrmConnector>> connectors_;
std::vector<std::unique_ptr<DrmConnector>> writeback_connectors_;