#hid #io #keyboard #daemon #linux #protocols #protocol #windows #cortex-m #keyboards

nightly hid-io-protocol

HID-IO protocol implementation for both servers and devices. Devices are optimized for Cortex-M devices, but may work for other platforms

1 unstable release

Uses new Rust 2021

0.1.0 Nov 12, 2021

#719 in Network programming

MIT license

150KB
3K SLoC

hid-io protocol

HID-IO Server and Device protocol implementation

This library can be integrated into both embedded and full user-space applications using the device and server feature flags.

The hid-io protocol library handles these features:

  • Buffer packetization and re-assembly
  • All the different packet types (Data, ACK, NAK, No ACK Data, Sync as well as the continued variations)
  • HID-IO Command processing (both send and receive)
  • 16 and 32-bit command IDs

Spec

HID-IO Protocol Spec

API Documentation

TODO

Building

Server Library

cargo build
cargo build --release

Device Library

cargo build --no-default-features --features device
cargo build --no-default-features --features device --release

Usage

There are two different ways to utilize hid-io-protocol as a server library.

  1. Ingest bytes, assemble buffer, handle message, create response buffer, serialize buffer, send bytes
  2. Ingest message buffer, handle message, create response buffer, send buffer

In each way a CommandInterface struct is created and the Commands trait is implemented. The implementation of CommandInterface is what differentiates betwen the two options.


Option 1 is simpler as hid-io-protocol can handle all processing from a hidraw interface. Device libraries usually go for this.

const BufChunk: usize = U64;
const IdLen: usize = U10;
const MessageLen: usize = U256;
const RxBuf: usize = U8;
const SerializationLen: usize = U276;
const TxBuf: usize = U8;

let ids = [
    HidIoCommandID::SupportedIDs,
    /* Add supported ids */
    /* This is the master list, if it's not listed here comamnds will not work */
];

let intf = CommandInterface::<TxBuf, RxBuf, BufChunk, MessageLen, {MessageLen - 1}, {MessageLen - 4}, SerializationLen, IdLen>::new(&ids).unwrap();
}

// The max length must equal BufChunk (e.g. 64 bytes)
// This may not be 64 bytes depending on your use-case and situation
// 63 bytes is common when you need to use a hid report id
let hidraw_buffer = read_hidraw();

// Enqueue bytes into buffer
intf.rx_bytebuf.enqueue(match Vec::from_slice(slice) {
    Ok(vec) => vec,
    Err(_) => {
        return HidioStatus::ErrorBufSizeTooSmall;
    }
}).unwrap();

// Process messages
// If any responses are created, they'll be sent out with intf.tx_bytebuf
intf.process_rx();

// Copy a single chunk from the tx_buffer
// You'll likely want to do this repeatedly until the buffer is empty
match intf.tx_bytebuf.dequeue() {
    Some(chunk) => {
        // Write to hidraw output buffer
        // Same size restrictions apply as above
        write_hidraw(chunk);
    }
    None => {}
}

struct CommandInterface<
    const TX: usize,
    const RX: usize,
    const N: usize,
    const H: usize,
    const HSUB1: usize,
    const HSUB4: usize,
    const S: usize,
    const ID: usize,
> {
    ids: Vec<HidIoCommandID, ID>,
    rx_bytebuf: buffer::Buffer<RX, N>,
    rx_packetbuf: HidIoPacketBuffer<H>,
    tx_bytebuf: buffer::Buffer<TX, N>,
    serial_buf: Vec<u8, S>,
}

impl<
        const TX: usize,
        const RX: usize,
        const N: usize,
        const H: usize,
        const HSUB1: usize,
        const HSUB4: usize,
        const S: usize,
        const ID: usize,
    > CommandInterface<TX, RX, N, H, HSUB1, HSUB4, S, ID>
{
    fn new(
        ids: &[HidIoCommandID],
    ) -> Result<CommandInterface<TX, RX, N, H, HSUB1, HSUB4, S, ID>, CommandError> {
        // Make sure we have a large enough id vec
        let ids = match Vec::from_slice(ids) {
            Ok(ids) => ids,
            Err(_) => {
                return Err(CommandError::IdVecTooSmall);
            }
        };

        let tx_bytebuf = buffer::Buffer::new();
        let rx_bytebuf = buffer::Buffer::new();
        let rx_packetbuf = HidIoPacketBuffer::new();
        let serial_buf = Vec::new();

        Ok(CommandInterface {
            ids,
            rx_bytebuf,
            rx_packetbuf,
            tx_bytebuf,
            serial_buf,
        })
    }

    /// Decode rx_bytebuf into a HidIoPacketBuffer
    /// Returns true if buffer ready, false if not
    fn rx_packetbuffer_decode(&mut self) -> Result<bool, CommandError> {
        loop {
            // Retrieve vec chunk
            if let Some(buf) = self.rx_bytebuf.dequeue() {
                // Decode chunk
                match self.rx_packetbuf.decode_packet(&buf) {
                    Ok(_recv) => {
                        // Only handle buffer if ready
                        if self.rx_packetbuf.done {
                            // Handle sync packet type
                            match self.rx_packetbuf.ptype {
                                HidIoPacketType::Sync => {
                                    // Clear buffer, packet missing
                                    self.rx_packetbuf.clear();
                                }
                                _ => {
                                    return Ok(true);
                                }
                            }
                        }
                    }
                    Err(e) => {
                        return Err(CommandError::PacketDecodeError(e));
                    }
                }
            } else {
                return Ok(false);
            }
        }
    }

    /// Process rx buffer until empty
    /// Handles flushing tx->rx, decoding, then processing buffers
    /// Returns the number of buffers processed
    pub fn process_rx(&mut self) -> Result<u8, CommandError> {
        // Decode bytes into buffer
        while (self.rx_packetbuffer_decode()? {
            // Process rx buffer
            self.rx_message_handling(self.rx_packetbuf.clone())?;

            // Clear buffer
            self.rx_packetbuf.clear();
        }

        Ok(cur)
    }
}

/// CommandInterface for Commands
/// TX - tx byte buffer size (in multiples of N)
/// RX - tx byte buffer size (in multiples of N)
/// N - Max payload length (HidIoPacketBuffer), used for default values
/// H - Max data payload length (HidIoPacketBuffer)
/// S - Serialization buffer size
/// ID - Max number of HidIoCommandIDs
impl<
        const TX: usize,
        const RX: usize,
        const N: usize,
        const H: usize,
        const HSUB1: usize,
        const HSUB4: usize,
        const S: usize,
        const ID: usize,
    > Commands<H, ID> for CommandInterface<TX, RX, N, H, HSUB1, HSUB4, S, ID> {
    fn default_packet_chunk(&self) -> u32 {
        N as u32
    }

    fn tx_packetbuffer_send(&mut self, buf: &mut HidIoPacketBuffer<H>) -> Result<(), CommandError> {
        let size = buf.serialized_len() as usize;
        if self.serial_buf.resize_default(size).is_err() {
            return Err(CommandError::SerializationVecTooSmall);
        }
        match buf.serialize_buffer(&mut self.serial_buf) {
            Ok(data) => data,
            Err(err) => {
                return Err(CommandError::SerializationFailed(err));
            }
        };

        // Add serialized data to buffer
        // May need to enqueue multiple packets depending how much
        // was serialized
        // The first byte is a serde type and is dropped
        let data = &self.serial_buf;
        for pos in (1..data.len()).step_by(N) {
            let len = core::cmp::min(N, data.len() - pos);
            match self
                .tx_bytebuf
                .enqueue(match Vec::from_slice(&data[pos..len + pos]) {
                    Ok(vec) => vec,
                    Err(_) => {
                        return Err(CommandError::TxBufferVecTooSmall);
                    }
                }) {
                Ok(_) => {}
                Err(_) => {
                    return Err(CommandError::TxBufferSendFailed);
                }
            }
        }
        Ok(())
    }
    fn supported_id(&self, id: HidIoCommandID) -> bool {
        /* Your implementation */
    }

    fn h0000_supported_ids_cmd(&mut self, _data: h0000::Cmd) -> Result<h0000::Ack<ID>, h0000::Nak> {
        /* Message specific commands are optional to implement */
    }
}

hid-io-core uses Option 2 as different threads handle byte ingest and message handling. You'll need to handle buffer assembly/disassembly yourself.

        struct CommandInterface {}
        impl Commands<mailbox::HidIoPacketBufferDataSize, 0> for CommandInterface {
            fn tx_packetbuffer_send(
                &mut self,
                buf: &mut mailbox::HidIoPacketBuffer,
            ) -> Result<(), CommandError> {
                /* Send command and wait for a reply */
                /* If sending an ACK/NAK or NA Data then there won't be a reply */

                if let Some(rcvmsg) = /* send buffer */ {
                    // Handle ack/nak
                    self.rx_message_handling(rcvmsg.data)?;
                }
                Ok(())
            }
            fn h0016_flashmode_ack(
                &mut self,
                data: h0016::Ack,
            ) -> Result<(), CommandError> {
                /* ACK */
                Ok(())
            }
            fn h0016_flashmode_nak(
                &mut self,
                data: h0016::Nak,
            ) -> Result<(), CommandError> {
                /* NAK */
                Ok(())
            }
        }
        let mut intf = CommandInterface {};

        // Send command
        intf.h0016_flashmode(h0016::Cmd {}).unwrap();

hidraw Setup

When using hid-io-protocol with device firmware you'll need to setup a hidraw interface. This should work the same for both USB, Bluetooth (and anything else that supports the USB HID spec). Option 1 in the usage examples has stubs indicating where hidraw rx and tx occur.

HID Descriptor

Below is an example hidraw HID descriptor for USB 2.0 FS using 64 byte packets.

    0x06, 0x1C, 0xFF,    // Usage Page (Vendor Defined) 0xFF1C
    0x0A, 0x00, 0x11,    // Usage 0x1100
    0xA1, 0x01,          // Collection (Application)
    0x75, 0x08,          //   Report Size (8)
    0x15, 0x00,          //   Logical Minimum (0)
    0x26, 0xFF, 0x00,    //   Logical Maximum (255)

    0x95, 0x40,          //     Report Count (64)
    0x09, 0x01,          //     Usage (Output)
    0x91, 0x02,          //     Output (Data,Var,Abs)

    0x95, 0x40,          //     Report Count (64)
    0x09, 0x02,          //     Usage (Input)
    0x81, 0x02,          //     Input (Data,Var,Abs)

    0xC0,                // End Collection

It's also possible to use Report Ids; however the report count should be adjusted to make sure you're not sending multiple USB packets for a single hidraw report. Adjust the Report Count fields accordingly.

USB Endpoint Setup

Below is an example of how to setup the USB endpoints for the above hid descriptor.

// --- Vendor Specific / RAW I/O ---
// - 9 bytes -
	// interface descriptor, USB spec 9.6.5, page 267-269, Table 9-12
	9,                                      // bLength
	4,                                      // bDescriptorType
	RAWIO_INTERFACE,                        // bInterfaceNumber
	0,                                      // bAlternateSetting
	2,                                      // bNumEndpoints
	0x03,                                   // bInterfaceClass (0x03)
	0x00,                                   // bInterfaceSubClass
	0x00,                                   // bInterfaceProtocol
	0,                                      // iInterface (can point to a string name if desired)

// - 9 bytes -
	// HID interface descriptor, HID 1.11 spec, section 6.2.1
	9,                                      // bLength
	0x21,                                   // bDescriptorType
	0x11, 0x01,                             // bcdHID
	0,                                      // bCountryCode
	1,                                      // bNumDescriptors
	0x22,                                   // bDescriptorType
	LSB(sizeof(rawio_report_desc)),         // wDescriptorLength
	MSB(sizeof(rawio_report_desc)),

// - 7 bytes -
	// endpoint descriptor, USB spec 9.6.6, page 269-271, Table 9-13
	7,                                      // bLength
	5,                                      // bDescriptorType
	RAWIO_TX_ENDPOINT | 0x80,               // bEndpointAddress
	0x03,                                   // bmAttributes (0x03=intr)
	0x40, 0,                                // wMaxPacketSize (64 bytes)
	1,                                      // bInterval

// - 7 bytes -
	// endpoint descriptor, USB spec 9.6.6, page 269-271, Table 9-13
	7,                                      // bLength
	5,                                      // bDescriptorType
	RAWIO_RX_ENDPOINT,                      // bEndpointAddress
	0x03,                                   // bmAttributes (0x03=intr)
	0x40, 0,                                // wMaxPacketSize (64 bytes)
	1,                                      // bInterval

Then all you should have to do is send and receive data to your specified endpoints RAWIO_TX_ENDPOINT and RAWIO_RX_ENDPOINT.

C Firmware Usage

See hid-io-kiibohd

Testing

cargo test

Some of the tests utilize additional logging so you can also do:

RUST_LOG=info cargo test

Dependencies

  • Rust nightly (may relax over time)
  • NOTE: bincode-core is so new it doesn't have a proper release yet and may break at any time.

Supported Server Applications

Supported Device Firmware

Contributing

  • Pull-requests run a variety of tests
  • When adding new messages, make sure to add a unit test validation
  • Some recommended tests:
    • cargo test
    • cargo build
    • cargo build --no-default-features --features device

Dependencies

~0.8–1.4MB
~30K SLoC