From 136b00ea3228ec8b8045698688ac7a52bcc3471d Mon Sep 17 00:00:00 2001
From: Leon Tan <leon.arian.tan@gmail.com>
Date: Mon, 29 Mar 2021 13:58:20 +0200
Subject: [PATCH] Implement alternate setting selection

---
 Cargo.toml    |  2 +-
 src/bus.rs    |  2 +-
 src/class.rs  | 20 +++++++++++++++++++-
 src/device.rs | 49 +++++++++++++++++++++++++++++++++++++++++++------
 4 files changed, 64 insertions(+), 9 deletions(-)

diff --git a/Cargo.toml b/Cargo.toml
index d582a0f..9009be6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "usb-device"
 description = "Experimental device-side USB stack for embedded devices."
-version = "0.2.8"
+version = "0.2.9"
 edition = "2018"
 readme = "README.md"
 keywords = ["no-std", "embedded", "usb"]
diff --git a/src/bus.rs b/src/bus.rs
index cd176d3..7604d17 100644
--- a/src/bus.rs
+++ b/src/bus.rs
@@ -281,7 +281,7 @@ impl<B: UsbBus> UsbBusAllocator<B> {
 
 /// A handle for a USB interface that contains its number.
 #[derive(Copy, Clone, Eq, PartialEq)]
-pub struct InterfaceNumber(u8);
+pub struct InterfaceNumber(pub(crate) u8);
 
 impl From<InterfaceNumber> for u8 {
     fn from(n: InterfaceNumber) -> u8 {
diff --git a/src/class.rs b/src/class.rs
index 5337e97..9e94484 100644
--- a/src/class.rs
+++ b/src/class.rs
@@ -1,4 +1,4 @@
-use crate::bus::{StringIndex, UsbBus};
+use crate::bus::{InterfaceNumber, StringIndex, UsbBus};
 use crate::control;
 use crate::control_pipe::ControlPipe;
 use crate::descriptor::{BosWriter, DescriptorWriter};
@@ -116,6 +116,24 @@ pub trait UsbClass<B: UsbBus> {
     fn endpoint_in_complete(&mut self, addr: EndpointAddress) {
         let _ = addr;
     }
+
+    /// Called when the interfaces alternate setting state is requested.
+    ///
+    /// Note: This method may be called on interfaces, that are not relevant to this class.
+    /// You should return `None, if `interface` belongs to an interface you don't know.
+    fn get_alt_setting(&mut self, interface: InterfaceNumber) -> Option<u8> {
+        let _ = interface;
+        None
+    }
+
+    /// Called when the interfaces alternate setting state is altered.
+    ///
+    /// Note: This method may be called on interfaces, that are not relevant to this class.
+    /// You should return `false`, if `interface` belongs to an interface you don't know.
+    fn set_alt_setting(&mut self, interface: InterfaceNumber, alternative: u8) -> bool {
+        let _ = (interface, alternative);
+        false
+    }
 }
 
 /// Handle for a control IN transfer. When implementing a class, use the methods of this object to
diff --git a/src/device.rs b/src/device.rs
index defc49c..fc102e1 100644
--- a/src/device.rs
+++ b/src/device.rs
@@ -1,4 +1,4 @@
-use crate::bus::{PollResult, StringIndex, UsbBus, UsbBusAllocator};
+use crate::bus::{InterfaceNumber, PollResult, StringIndex, UsbBus, UsbBusAllocator};
 use crate::class::{ControlIn, ControlOut, UsbClass};
 use crate::control;
 use crate::control_pipe::ControlPipe;
@@ -338,7 +338,25 @@ impl<B: UsbBus> UsbDevice<'_, B> {
                 }
 
                 (Recipient::Interface, Request::GET_INTERFACE) => {
-                    // TODO: change when alternate settings are implemented
+                    // Reject interface numbers bigger than 255
+                    if req.index > core::u8::MAX.into() {
+                        xfer.reject().ok();
+                        return;
+                    }
+
+                    // Ask class implementations, whether they know the alternate setting
+                    // of the interface in question
+                    for cls in classes {
+                        match cls.get_alt_setting(InterfaceNumber(req.index as u8)) {
+                            Some(setting) => {
+                                xfer.accept_with(&setting.to_le_bytes()).ok();
+                                return;
+                            }
+                            None => (),
+                        }
+                    }
+
+                    // If no class returned an alternate setting, return the default value
                     xfer.accept_with(&DEFAULT_ALTERNATE_SETTING.to_le_bytes())
                         .ok();
                 }
@@ -355,7 +373,7 @@ impl<B: UsbBus> UsbDevice<'_, B> {
     fn control_out(&mut self, classes: &mut ClassList<'_, B>, req: control::Request) {
         use crate::control::{Recipient, Request};
 
-        for cls in classes {
+        for cls in classes.iter_mut() {
             cls.control_out(ControlOut::new(&mut self.control, &req));
 
             if !self.control.waiting_for_response() {
@@ -428,9 +446,28 @@ impl<B: UsbBus> UsbDevice<'_, B> {
                     }
                 }
 
-                (Recipient::Interface, Request::SET_INTERFACE, DEFAULT_ALTERNATE_SETTING_U16) => {
-                    // TODO: do something when alternate settings are implemented
-                    xfer.accept().ok();
+                (Recipient::Interface, Request::SET_INTERFACE, alt_setting) => {
+                    // Reject interface numbers and alt settings bigger than 255
+                    if req.index > core::u8::MAX.into() || alt_setting > core::u8::MAX.into() {
+                        xfer.reject().ok();
+                        return;
+                    }
+
+                    // Ask class implementations, whether they accept the alternate interface setting.
+                    for cls in classes {
+                        if cls.set_alt_setting(InterfaceNumber(req.index as u8), alt_setting as u8)
+                        {
+                            xfer.accept().ok();
+                            return;
+                        }
+                    }
+
+                    // Default behaviour, if no class implementation accepted the alternate setting.
+                    if alt_setting == DEFAULT_ALTERNATE_SETTING_U16 {
+                        xfer.accept().ok();
+                    } else {
+                        xfer.reject().ok();
+                    }
                 }
 
                 _ => {