Allow creating multiple MIDI in and out jacks

src/midi_device.rs

@@ -16,7 +16,9 @@ pub struct MidiClass<'a,B: UsbBus> {
     standard_ac: InterfaceNumber,
     standard_mc: InterfaceNumber,
     standard_bulkout: EndpointOut<'a, B>,
-    standard_bulkin: EndpointIn<'a,B>
+    standard_bulkin: EndpointIn<'a,B>,
+    n_in_jacks: u8,
+    n_out_jacks: u8,
 }
 
 pub enum MidiReadError {
@@ -24,15 +26,25 @@ pub enum MidiReadError {
     UsbError(UsbError)
 }
 
+#[derive(Debug)]
+pub struct InvalidArguments;
+
 impl<B: UsbBus> MidiClass<'_, B> {
-    /// Creates a new MidiClass with the provided UsbBus
-    pub fn new(alloc: &UsbBusAllocator<B>) -> MidiClass<'_, B> {
-        MidiClass {
+    /// Creates a new MidiClass with the provided UsbBus and `n_in/out_jacks` embedded input/output jacks (or "cables",
+    /// depending on the terminology).
+    /// Note that a maximum of 16 in and 16 out jacks are supported.
+    pub fn new(alloc: &UsbBusAllocator<B>, n_in_jacks: u8, n_out_jacks: u8) -> core::result::Result<MidiClass<'_, B>, InvalidArguments>  {
+        if n_in_jacks >= 16 || n_out_jacks >= 16 {
+            return Err(InvalidArguments);
+        }
+        Ok(MidiClass {
             standard_ac: alloc.interface(),
             standard_mc: alloc.interface(),
             standard_bulkout : alloc.bulk(MAX_PACKET_SIZE as u16),
-            standard_bulkin: alloc.bulk(MAX_PACKET_SIZE as u16)
-        }
+            standard_bulkin: alloc.bulk(MAX_PACKET_SIZE as u16),
+            n_in_jacks,
+            n_out_jacks
+        })
     }
 
     pub fn send_message(&mut self, usb_midi:UsbMidiEventPacket) -> Result<usize> {
@@ -43,14 +55,21 @@ impl<B: UsbBus> MidiClass<'_, B> {
     pub fn read(&mut self, buffer: &mut [u8]) -> Result<usize> {
         self.standard_bulkout.read(buffer)
     }
+
+    /// calculates the index'th midi in jack id
+    fn in_jack_id(&self, index: u8) -> u8 {
+        return index + 1;
+    }
+    /// calculates the index'th midi in jack id
+    fn out_jack_id(&self, index: u8) -> u8 {
+        return self.n_in_jacks + index + 1;
+    }
 }
 
 impl<B: UsbBus> UsbClass<B> for MidiClass<'_, B> {
 
      fn get_configuration_descriptors(&self, writer: &mut DescriptorWriter) -> Result<()> {
-        
         //AUDIO CONTROL STANDARD
-
         writer.interface(
             self.standard_ac,
             USB_AUDIO_CLASS,
@@ -79,64 +98,80 @@ impl<B: UsbBus> UsbClass<B> for MidiClass<'_, B> {
             0, //no protocol
         )?; //Num endpoints?
 
-        //Streaming extra info
+        let midi_streaming_start_byte = writer.position();
+        let midi_streaming_total_length =
+            7 + self.n_in_jacks as usize * MIDI_IN_SIZE as usize + self.n_out_jacks as usize * MIDI_OUT_SIZE as usize
+            + 7 + (4+self.n_in_jacks as usize) + 7 + (4+self.n_out_jacks as usize);
 
-        writer.write(
+        //Streaming extra info
+        writer.write( // len = 7
             CS_INTERFACE,
             &[
                 MS_HEADER_SUBTYPE,
                 0x00,0x01, //REVISION
-                (0x07 + MIDI_OUT_SIZE),0x00 //Total size of class specific descriptors? (little endian?)
+                (midi_streaming_total_length & 0xFF) as u8, ((midi_streaming_total_length >> 8) & 0xFF) as u8
             ]
         )?;
-    
+
         //JACKS
+        for i in 0..self.n_in_jacks {
+            writer.write( // len = 6 = MIDI_IN_SIZE
+                CS_INTERFACE,
+                &[
+                    MIDI_IN_JACK_SUBTYPE,
+                    EMBEDDED,
+                    self.in_jack_id(i), // id
+                    0x00
+                ]
+            )?;
+        }
 
-        writer.write(
-            CS_INTERFACE,
-            &[
-                MIDI_IN_JACK_SUBTYPE,
-                EMBEDDED,
-                0x01, // id
-                0x00
-            ]
-        )?;
+        for i in 0..self.n_out_jacks {
+            writer.write ( // len = 9 = MIDI_OUT_SIZE
+                CS_INTERFACE,
+                &[
+                    MIDI_OUT_JACK_SUBTYPE,
+                    EMBEDDED,
+                    self.out_jack_id(i), //id
+                    0x01, // 1 pin
+                    self.in_jack_id(i), // pin 1
+                    0x01, //sorta vague source pin?
+                    0x00
+                ]
+            )?;
+        }
 
-        writer.write (
-            CS_INTERFACE,
-            &[
-                MIDI_OUT_JACK_SUBTYPE,
-                EMBEDDED,
-                0x01,//id
-                0x01, // 1 pin
-                0x01, // pin 1
-                0x01, //sorta vague source pin?
-                0x00
-            ]
-        )?;
+        let mut endpoint_data = [
+            MS_GENERAL,
+            0, // number of jacks. must be filled in!
+            0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 // jack mappings. must be filled in and cropped.
+        ];
 
-        writer.endpoint(&self.standard_bulkout)?;
+        writer.endpoint(&self.standard_bulkout)?; // len = 7
 
-        writer.write(
+        endpoint_data[1] = self.n_in_jacks;
+        for i in 0..self.n_in_jacks {
+            endpoint_data[2 + i as usize] = self.in_jack_id(i);
+        }
+        writer.write( // len = 4 + self.n_in_jacks
             CS_ENDPOINT,
-            &[
-                MS_GENERAL,
-                0x01,
-                0x01
-            ]
+            &endpoint_data[0..2+self.n_in_jacks as usize]
         )?;
 
-        writer.endpoint(&self.standard_bulkin)?;
-
-        writer.write(
+        writer.endpoint(&self.standard_bulkin)?; // len = 7
+        endpoint_data[1] = self.n_out_jacks;
+        for i in 0..self.n_out_jacks {
+            endpoint_data[2 + i as usize] = self.out_jack_id(i);
+        }
+        writer.write( // len = 4 + self.n_out_jacks
             CS_ENDPOINT,
-            &[
-                MS_GENERAL,
-                0x01,
-                0x01
-            ]
+            &endpoint_data[0..2+self.n_out_jacks as usize]
         )?;
+
+        let midi_streaming_end_byte = writer.position();
+        assert!(midi_streaming_end_byte - midi_streaming_start_byte == midi_streaming_total_length);
+
         Ok(())
     }
 
-}
+}