add support for alternate settings

Author: kiffie

Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "usb-device"
 description = "Experimental device-side USB stack for embedded devices."
-version = "0.2.7"
+version = "0.3.0"
 edition = "2018"
 readme = "README.md"
 keywords = ["no-std", "embedded", "usb"]

src/descriptor.rs

@@ -1,5 +1,5 @@
 use crate::{Result, UsbError};
-use crate::bus::{UsbBus, InterfaceNumber};
+use crate::bus::{UsbBus, InterfaceNumber, StringIndex};
 use crate::device;
 use crate::endpoint::{Endpoint, EndpointDirection};
 
@@ -175,24 +175,64 @@ impl DescriptorWriter<'_> {
     pub fn interface(&mut self, number: InterfaceNumber,
         interface_class: u8, interface_sub_class: u8, interface_protocol: u8) -> Result<()>
     {
-        match self.num_interfaces_mark {
-            Some(mark) => self.buf[mark] += 1,
-            None => return Err(UsbError::InvalidState),
+        self.interface_alternate_setting(
+            number,
+            device::DEFAULT_ALTERNATE_SETTING,
+            interface_class,
+            interface_sub_class,
+            interface_protocol,
+            None,
+        )
+    }
+
+    /// Writes a interface descriptor with a specific alternate setting and
+    /// interface string identifier.
+    ///
+    /// # Arguments
+    ///
+    /// * `number` - Interface number previously allocated with
+    ///   [`UsbBusAllocator::interface`](crate::bus::UsbBusAllocator::interface).
+    /// * `alternate_setting` - number of the alternate setting
+    /// * `interface_class` - Class code assigned by USB.org. Use `0xff` for vendor-specific devices
+    ///   that do not conform to any class.
+    /// * `interface_sub_class` - Sub-class code. Depends on class.
+    /// * `interface_protocol` - Protocol code. Depends on class and sub-class.
+    /// * `interface_string` - Index of string descriptor describing this interface
+
+    pub fn interface_alternate_setting(
+        &mut self,
+        number: InterfaceNumber,
+        alternate_setting: u8,
+        interface_class: u8,
+        interface_sub_class: u8,
+        interface_protocol: u8,
+        interface_string: Option<StringIndex>,
+    ) -> Result<()> {
+        let ifndx = match interface_string {
+            Some(si) => si.into(),
+            None => 0,
         };
+        if alternate_setting == device::DEFAULT_ALTERNATE_SETTING {
+            match self.num_interfaces_mark {
+                Some(mark) => self.buf[mark] += 1,
+                None => return Err(UsbError::InvalidState),
+            };
+        }
 
         self.num_endpoints_mark = Some(self.position + 4);
 
         self.write(
             descriptor_type::INTERFACE,
             &[
-                number.into(), // bInterfaceNumber
-                device::DEFAULT_ALTERNATE_SETTING, // bAlternateSetting (how to even handle these...)
-                0, // bNumEndpoints
-                interface_class, // bInterfaceClass
+                number.into(),       // bInterfaceNumber
+                alternate_setting,   // bAlternateSetting (how to even handle these...)
+                0,                   // bNumEndpoints
+                interface_class,     // bInterfaceClass
                 interface_sub_class, // bInterfaceSubClass
-                interface_protocol, // bInterfaceProtocol
-                0, // iInterface
-            ])?;
+                interface_protocol,  // bInterfaceProtocol
+                ifndx,               // iInterface
+            ],
+        )?;
 
         Ok(())
     }
@@ -318,4 +358,4 @@ impl<'w, 'a: 'w> BosWriter<'w, 'a> {
         let position = self.writer.position as u16;
         self.writer.buf[2..4].copy_from_slice(&position.to_le_bytes());
     }
-}
+}