Merge #1180

1180: usb: allow adding isochronous endpoints r=Dirbaio a=nitroxis

This adds (basic) support for isochronous endpoints. In theory, isochronous endpoints have guaranteed bandwidths and are support to adhere to strict timings. But it seems that nothing bad happens if you don't follow the specs closely in this regard. Better handling could also still be added in the future.

Co-authored-by: nitroxis <n@nxs.re>

embassy-usb/src/builder.rs

@@ -401,4 +401,17 @@ impl<'a, 'd, D: Driver<'d>> InterfaceAltBuilder<'a, 'd, D> {
     pub fn endpoint_interrupt_out(&mut self, max_packet_size: u16, interval: u8) -> D::EndpointOut {
         self.endpoint_out(EndpointType::Interrupt, max_packet_size, interval)
     }
+
+    /// Allocate a ISOCHRONOUS IN endpoint and write its descriptor.
+    ///
+    /// Descriptors are written in the order builder functions are called. Note that some
+    /// classes care about the order.
+    pub fn endpoint_isochronous_in(&mut self, max_packet_size: u16, interval: u8) -> D::EndpointIn {
+        self.endpoint_in(EndpointType::Isochronous, max_packet_size, interval)
+    }
+
+    /// Allocate a ISOCHRONOUS OUT endpoint and write its descriptor.
+    pub fn endpoint_isochronous_out(&mut self, max_packet_size: u16, interval: u8) -> D::EndpointOut {
+        self.endpoint_out(EndpointType::Isochronous, max_packet_size, interval)
+    }
 }