/
descriptor.rs
336 lines (291 loc) · 11 KB
/
descriptor.rs
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//! Utilities for writing USB descriptors.
use crate::builder::Config;
use crate::driver::EndpointInfo;
use crate::types::{InterfaceNumber, StringIndex};
use crate::CONFIGURATION_VALUE;
/// Standard descriptor types
#[allow(missing_docs)]
pub mod descriptor_type {
pub const DEVICE: u8 = 1;
pub const CONFIGURATION: u8 = 2;
pub const STRING: u8 = 3;
pub const INTERFACE: u8 = 4;
pub const ENDPOINT: u8 = 5;
pub const IAD: u8 = 11;
pub const BOS: u8 = 15;
pub const CAPABILITY: u8 = 16;
}
/// String descriptor language IDs.
pub mod lang_id {
/// English (US)
///
/// Recommended for use as the first language ID for compatibility.
pub const ENGLISH_US: u16 = 0x0409;
}
/// Standard capability descriptor types
#[allow(missing_docs)]
pub mod capability_type {
pub const WIRELESS_USB: u8 = 1;
pub const USB_2_0_EXTENSION: u8 = 2;
pub const SS_USB_DEVICE: u8 = 3;
pub const CONTAINER_ID: u8 = 4;
pub const PLATFORM: u8 = 5;
}
/// A writer for USB descriptors.
pub(crate) struct DescriptorWriter<'a> {
pub buf: &'a mut [u8],
position: usize,
num_interfaces_mark: Option<usize>,
num_endpoints_mark: Option<usize>,
}
impl<'a> DescriptorWriter<'a> {
pub(crate) fn new(buf: &'a mut [u8]) -> Self {
DescriptorWriter {
buf,
position: 0,
num_interfaces_mark: None,
num_endpoints_mark: None,
}
}
pub fn into_buf(self) -> &'a mut [u8] {
&mut self.buf[..self.position]
}
/// Gets the current position in the buffer, i.e. the number of bytes written so far.
pub const fn position(&self) -> usize {
self.position
}
/// Writes an arbitrary (usually class-specific) descriptor.
pub fn write(&mut self, descriptor_type: u8, descriptor: &[u8]) {
let length = descriptor.len();
assert!(
(self.position + 2 + length) <= self.buf.len() && (length + 2) <= 255,
"Descriptor buffer full"
);
self.buf[self.position] = (length + 2) as u8;
self.buf[self.position + 1] = descriptor_type;
let start = self.position + 2;
self.buf[start..start + length].copy_from_slice(descriptor);
self.position = start + length;
}
pub(crate) fn configuration(&mut self, config: &Config) {
self.num_interfaces_mark = Some(self.position + 4);
self.write(
descriptor_type::CONFIGURATION,
&[
0,
0, // wTotalLength
0, // bNumInterfaces
CONFIGURATION_VALUE, // bConfigurationValue
0, // iConfiguration
0x80 | if config.self_powered { 0x40 } else { 0x00 }
| if config.supports_remote_wakeup { 0x20 } else { 0x00 }, // bmAttributes
(config.max_power / 2) as u8, // bMaxPower
],
);
}
#[allow(unused)]
pub(crate) fn end_class(&mut self) {
self.num_endpoints_mark = None;
}
pub(crate) fn end_configuration(&mut self) {
let position = self.position as u16;
self.buf[2..4].copy_from_slice(&position.to_le_bytes());
}
/// Writes a interface association descriptor. Call from `UsbClass::get_configuration_descriptors`
/// before writing the USB class or function's interface descriptors if your class has more than
/// one interface and wants to play nicely with composite devices on Windows. If the USB device
/// hosting the class was not configured as composite with IADs enabled, calling this function
/// does nothing, so it is safe to call from libraries.
///
/// # Arguments
///
/// * `first_interface` - Number of the function's first interface, previously allocated with
/// [`UsbDeviceBuilder::interface`](crate::bus::UsbDeviceBuilder::interface).
/// * `interface_count` - Number of interfaces in the function.
/// * `function_class` - Class code assigned by USB.org. Use `0xff` for vendor-specific devices
/// 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.
pub fn iad(
&mut self,
first_interface: InterfaceNumber,
interface_count: u8,
function_class: u8,
function_sub_class: u8,
function_protocol: u8,
) {
self.write(
descriptor_type::IAD,
&[
first_interface.into(), // bFirstInterface
interface_count, // bInterfaceCount
function_class,
function_sub_class,
function_protocol,
0,
],
);
}
/// Writes a interface descriptor with a specific alternate setting and
/// interface string identifier.
///
/// # Arguments
///
/// * `number` - Interface number previously allocated with
/// [`UsbDeviceBuilder::interface`](crate::bus::UsbDeviceBuilder::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_alt(
&mut self,
number: InterfaceNumber,
alternate_setting: u8,
interface_class: u8,
interface_sub_class: u8,
interface_protocol: u8,
interface_string: Option<StringIndex>,
) {
if alternate_setting == 0 {
match self.num_interfaces_mark {
Some(mark) => self.buf[mark] += 1,
None => {
panic!("you can only call `interface/interface_alt` after `configuration`.")
}
};
}
let str_index = interface_string.map_or(0, Into::into);
self.num_endpoints_mark = Some(self.position + 4);
self.write(
descriptor_type::INTERFACE,
&[
number.into(), // bInterfaceNumber
alternate_setting, // bAlternateSetting
0, // bNumEndpoints
interface_class, // bInterfaceClass
interface_sub_class, // bInterfaceSubClass
interface_protocol, // bInterfaceProtocol
str_index, // iInterface
],
);
}
/// Writes an endpoint descriptor.
///
/// # Arguments
///
/// * `endpoint` - Endpoint previously allocated with
/// [`UsbDeviceBuilder`](crate::bus::UsbDeviceBuilder).
pub fn endpoint(&mut self, endpoint: &EndpointInfo) {
match self.num_endpoints_mark {
Some(mark) => self.buf[mark] += 1,
None => panic!("you can only call `endpoint` after `interface/interface_alt`."),
};
self.write(
descriptor_type::ENDPOINT,
&[
endpoint.addr.into(), // bEndpointAddress
endpoint.ep_type as u8, // bmAttributes
endpoint.max_packet_size as u8,
(endpoint.max_packet_size >> 8) as u8, // wMaxPacketSize
endpoint.interval_ms, // bInterval
],
);
}
/// Writes a string descriptor.
#[allow(unused)]
pub(crate) fn string(&mut self, string: &str) {
let mut pos = self.position;
assert!(pos + 2 <= self.buf.len(), "Descriptor buffer full");
self.buf[pos] = 0; // length placeholder
self.buf[pos + 1] = descriptor_type::STRING;
pos += 2;
for c in string.encode_utf16() {
assert!(pos < self.buf.len(), "Descriptor buffer full");
self.buf[pos..pos + 2].copy_from_slice(&c.to_le_bytes());
pos += 2;
}
self.buf[self.position] = (pos - self.position) as u8;
self.position = pos;
}
}
/// Create a new Device Descriptor array.
///
/// All device descriptors are always 18 bytes, so there's no need for
/// a variable-length buffer or DescriptorWriter.
pub(crate) fn device_descriptor(config: &Config) -> [u8; 18] {
[
18, // bLength
0x01, // bDescriptorType
0x10,
0x02, // bcdUSB 2.1
config.device_class, // bDeviceClass
config.device_sub_class, // bDeviceSubClass
config.device_protocol, // bDeviceProtocol
config.max_packet_size_0, // bMaxPacketSize0
config.vendor_id as u8,
(config.vendor_id >> 8) as u8, // idVendor
config.product_id as u8,
(config.product_id >> 8) as u8, // idProduct
config.device_release as u8,
(config.device_release >> 8) as u8, // bcdDevice
config.manufacturer.map_or(0, |_| 1), // iManufacturer
config.product.map_or(0, |_| 2), // iProduct
config.serial_number.map_or(0, |_| 3), // iSerialNumber
1, // bNumConfigurations
]
}
/// A writer for Binary Object Store descriptor.
pub struct BosWriter<'a> {
pub(crate) writer: DescriptorWriter<'a>,
num_caps_mark: Option<usize>,
}
impl<'a> BosWriter<'a> {
pub(crate) const fn new(writer: DescriptorWriter<'a>) -> Self {
Self {
writer,
num_caps_mark: None,
}
}
pub(crate) fn bos(&mut self) {
self.num_caps_mark = Some(self.writer.position + 4);
self.writer.write(
descriptor_type::BOS,
&[
0x00, 0x00, // wTotalLength
0x00, // bNumDeviceCaps
],
);
self.capability(capability_type::USB_2_0_EXTENSION, &[0; 4]);
}
/// Writes capability descriptor to a BOS
///
/// # Arguments
///
/// * `capability_type` - Type of a capability
/// * `data` - Binary data of the descriptor
pub fn capability(&mut self, capability_type: u8, data: &[u8]) {
match self.num_caps_mark {
Some(mark) => self.writer.buf[mark] += 1,
None => panic!("called `capability` not between `bos` and `end_bos`."),
}
let mut start = self.writer.position;
let blen = data.len();
assert!(
(start + blen + 3) <= self.writer.buf.len() && (blen + 3) <= 255,
"Descriptor buffer full"
);
self.writer.buf[start] = (blen + 3) as u8;
self.writer.buf[start + 1] = descriptor_type::CAPABILITY;
self.writer.buf[start + 2] = capability_type;
start += 3;
self.writer.buf[start..start + blen].copy_from_slice(data);
self.writer.position = start + blen;
}
pub(crate) fn end_bos(&mut self) {
self.num_caps_mark = None;
let position = self.writer.position as u16;
self.writer.buf[2..4].copy_from_slice(&position.to_le_bytes());
}
}