add doc and changelog, reverse change for StringIndex

Author: eZioPan

CHANGELOG.md

@@ -13,6 +13,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 * Added support for alternate settings on interfaces ([#114](https://github.com/rust-embedded-community/usb-device/pull/114)).
 * Added support for architectures without atomics ([#115](https://github.com/rust-embedded-community/usb-device/pull/115)).
 
+### Breaking
+* `DescriptorWriter::iad()` now requires a `Option<StringIndex>` to optionally specify a string for describing the function (#[121](https://github.com/rust-embedded-community/usb-device/pull/121/files))
+
 ### Changed
 * `EndpointType` enum now has fields for isochronous synchronization and usage ([#60](https://github.com/rust-embedded-community/usb-device/pull/60)).
 

src/bus.rs

@@ -334,9 +334,9 @@ impl From<InterfaceNumber> for u8 {
 #[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub struct StringIndex(u8);
 
-impl From<u8> for StringIndex {
-    fn from(i: u8) -> StringIndex {
-        StringIndex(i)
+impl StringIndex {
+    pub(crate) fn new(index: u8) -> StringIndex {
+        StringIndex(index)
     }
 }
 

src/descriptor.rs

@@ -178,6 +178,7 @@ impl DescriptorWriter<'_> {
     ///   that do not conform to any class.
     /// * `function_sub_class` - Sub-class code. Depends on class.
     /// * `function_protocol` - Protocol code. Depends on class and sub-class.
+    /// * `function_string` - Index of string descriptor describing this function
     pub fn iad(
         &mut self,
         first_interface: InterfaceNumber,

src/device.rs

@@ -1,4 +1,4 @@
-use crate::bus::{InterfaceNumber, PollResult, UsbBus, UsbBusAllocator};
+use crate::bus::{InterfaceNumber, PollResult, StringIndex, UsbBus, UsbBusAllocator};
 use crate::class::{ControlIn, ControlOut, UsbClass};
 use crate::control;
 use crate::control_pipe::ControlPipe;
@@ -558,12 +558,12 @@ impl<B: UsbBus> UsbDevice<'_, B> {
                         2 => config.product,
                         3 => config.serial_number,
                         _ => {
-                            let str_index = index.into();
+                            let index = StringIndex::new(index);
                             let lang_id = req.index;
 
                             classes
                                 .iter()
-                                .filter_map(|cls| cls.get_string(str_index, lang_id))
+                                .filter_map(|cls| cls.get_string(index, lang_id))
                                 .next()
                         }
                     };