hid: make the report protocol changeable during the lifetime of the a…

…pplication

c2usb/hid/application.hpp

@@ -37,10 +37,10 @@ class application : public polymorphic
 {
   public:
     constexpr explicit application(const report_protocol& rp)
-        : report_info_(rp)
+        : report_info_(&rp)
     {}
 
-    constexpr const report_protocol& report_info() const { return report_info_; }
+    constexpr const report_protocol& report_info() const { return *report_info_; }
 
   private: // internal behavior to override
     /// @brief Initialize the application when the protocol has been (possibly implicitly) selected.
@@ -143,6 +143,14 @@ class application : public polymorphic
         return receive_report(std::span<uint8_t>(report->data(), sizeof(*report)), report->type());
     }
 
+    /// @brief  Changes the report information on the fly. This is extremely rarely needed.
+    /// @param  rp: the new report protocol to use
+    void set_report_info(const report_protocol& rp)
+    {
+        // assert(!has_transport());
+        report_info_ = &rp;
+    }
+
   public:
     // SPEC WTF: The IDLE parameter is meant to control how often the device should resend
     // the same piece of information. This is introduced in the USB HID class spec,
@@ -189,7 +197,7 @@ class application : public polymorphic
     }
 
   private:
-    const report_protocol& report_info_;
+    const report_protocol* report_info_;
     std::atomic<transport*> transport_{};
 };