very, very simple WP with midi CC out

include/libremidi/backends/alsa_seq_ump/config.hpp

@@ -0,0 +1,53 @@
+#pragma once
+#include <libremidi/backends/alsa_seq/config.hpp>
+
+#if __has_include(<alsa/asoundlib.h>)
+  #include <alsa/asoundlib.h>
+#endif
+
+// Necessary for the versions of ALSA that did have UMP
+// through snd_seq_event, before snd_seq_ump_event existed.
+extern "C" {
+typedef struct snd_seq_ump_event snd_seq_ump_event_t;
+}
+
+namespace libremidi::alsa_seq_ump
+{
+
+struct poll_parameters
+{
+  snd_seq_addr_t addr{};
+  std::function<int(const snd_seq_ump_event_t&)> callback;
+};
+
+struct input_configuration
+{
+  using poll_parameters_type = poll_parameters;
+
+  std::string client_name = "libremidi client";
+  snd_seq_t* context{};
+  std::function<bool(const poll_parameters&)> manual_poll;
+  std::function<bool(snd_seq_addr_t)> stop_poll;
+
+  static constexpr int midi_version = 2;
+};
+
+struct output_configuration
+{
+  std::string client_name = "libremidi client";
+  snd_seq_t* context{};
+
+  static constexpr int midi_version = 2;
+};
+
+struct observer_configuration
+{
+  std::string client_name = "libremidi client";
+  snd_seq_t* context{};
+  std::function<bool(const libremidi::alsa_seq::poll_parameters&)> manual_poll;
+  std::function<bool(snd_seq_addr_t)> stop_poll;
+
+  static constexpr int midi_version = 2;
+};
+
+}