capsules_core/i2c_master_slave_driver.rs
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// Licensed under the Apache License, Version 2.0 or the MIT License.
// SPDX-License-Identifier: Apache-2.0 OR MIT
// Copyright Tock Contributors 2022.
//! Provides both an I2C Master and I2C Slave interface to userspace.
//!
//! By calling `listen` this module will wait for I2C messages
//! send to it by other masters on the I2C bus. If this device wants to
//! transmit as an I2C master, this module will put the I2C hardware in master
//! mode, transmit the read/write, then go back to listening (if listening
//! was enabled).
//!
//! This capsule must sit directly above the I2C HIL interface (and not
//! on top of the mux) because there is no way to mux the slave (it can't
//! listen on more than one address) and because the application may want
//! to be able to talk to any I2C address.
use core::cell::Cell;
use core::cmp;
use kernel::hil;
use kernel::processbuffer::{ReadableProcessBuffer, WriteableProcessBuffer};
use kernel::syscall::{CommandReturn, SyscallDriver};
use kernel::utilities::cells::{OptionalCell, TakeCell};
use kernel::{ErrorCode, ProcessId};
use kernel::grant::{AllowRoCount, AllowRwCount, Grant, UpcallCount};
pub const BUFFER_LENGTH: usize = 256;
/// Syscall driver number.
use crate::driver;
pub const DRIVER_NUM: usize = driver::NUM::I2cMasterSlave as usize;
/// Ids for read-only allow buffers
mod ro_allow {
pub const MASTER_TX: usize = 0;
pub const SLAVE_TX: usize = 2;
/// The number of allow buffers the kernel stores for this grant
pub const COUNT: u8 = 3;
}
/// Ids for read-write allow buffers
mod rw_allow {
pub const MASTER_RX: usize = 1;
pub const SLAVE_RX: usize = 3;
/// The number of allow buffers the kernel stores for this grant
pub const COUNT: u8 = 4;
}
#[derive(Default)]
pub struct App;
#[derive(Clone, Copy, PartialEq)]
enum MasterAction {
Read(u8),
Write,
WriteRead(u8),
}
pub struct I2CMasterSlaveDriver<'a, I: hil::i2c::I2CMasterSlave<'a>> {
i2c: &'a I,
listening: Cell<bool>,
master_action: Cell<MasterAction>, // Whether we issued a write or read as master
master_buffer: TakeCell<'static, [u8]>,
slave_buffer1: TakeCell<'static, [u8]>,
slave_buffer2: TakeCell<'static, [u8]>,
app: OptionalCell<ProcessId>,
apps: Grant<
App,
UpcallCount<1>,
AllowRoCount<{ ro_allow::COUNT }>,
AllowRwCount<{ rw_allow::COUNT }>,
>,
}
impl<'a, I: hil::i2c::I2CMasterSlave<'a>> I2CMasterSlaveDriver<'a, I> {
pub fn new(
i2c: &'a I,
master_buffer: &'static mut [u8],
slave_buffer1: &'static mut [u8],
slave_buffer2: &'static mut [u8],
grant: Grant<
App,
UpcallCount<1>,
AllowRoCount<{ ro_allow::COUNT }>,
AllowRwCount<{ rw_allow::COUNT }>,
>,
) -> I2CMasterSlaveDriver<'a, I> {
I2CMasterSlaveDriver {
i2c,
listening: Cell::new(false),
master_action: Cell::new(MasterAction::Write),
master_buffer: TakeCell::new(master_buffer),
slave_buffer1: TakeCell::new(slave_buffer1),
slave_buffer2: TakeCell::new(slave_buffer2),
app: OptionalCell::empty(),
apps: grant,
}
}
}
impl<'a, I: hil::i2c::I2CMasterSlave<'a>> hil::i2c::I2CHwMasterClient
for I2CMasterSlaveDriver<'a, I>
{
fn command_complete(&self, buffer: &'static mut [u8], status: Result<(), hil::i2c::Error>) {
// Map I2C error to a number we can pass back to the application
let status = kernel::errorcode::into_statuscode(match status {
Ok(()) => Ok(()),
Err(e) => Err(e.into()),
});
// Signal the application layer. Need to copy read in bytes if this
// was a read call.
match self.master_action.get() {
MasterAction::Write => {
self.master_buffer.replace(buffer);
self.app.map(|app| {
let _ = self.apps.enter(app, |_, kernel_data| {
kernel_data.schedule_upcall(0, (0, status, 0)).ok();
});
});
}
MasterAction::Read(read_len) => {
self.app.map(|app| {
let _ = self.apps.enter(app, |_, kernel_data| {
// Because this (somewhat incorrectly) doesn't report
// back how many bytes were read, the result of mut_enter
// is ignored. Note that this requires userspace to keep
// track of this information, and if read_len is longer
// than the buffer could lead to array overrun errors in
// userspace. The I2C syscall API should pass back lengths.
// -pal 3/5/21
kernel_data
.get_readwrite_processbuffer(rw_allow::MASTER_RX)
.and_then(|master_rx| {
master_rx.mut_enter(move |app_buffer| {
let len = cmp::min(app_buffer.len(), read_len as usize);
for (i, c) in buffer[0..len].iter().enumerate() {
app_buffer[i].set(*c);
}
self.master_buffer.replace(buffer);
0
})
})
.unwrap_or(0);
kernel_data.schedule_upcall(0, (1, status, 0)).ok();
});
});
}
MasterAction::WriteRead(read_len) => {
self.app.map(|app| {
let _ = self.apps.enter(app, |_, kernel_data| {
// Because this (somewhat incorrectly) doesn't report
// back how many bytes were read, the result of mut_enter
// is ignored. Note that this requires userspace to keep
// track of this information, and if read_len is longer
// than the buffer could lead to array overrun errors in
// userspace. The I2C syscall API should pass back lengths.
// -pal 3/5/21
kernel_data
.get_readwrite_processbuffer(rw_allow::MASTER_RX)
.and_then(|master_rx| {
master_rx.mut_enter(move |app_buffer| {
let len = cmp::min(app_buffer.len(), read_len as usize);
app_buffer[..len].copy_from_slice(&buffer[..len]);
self.master_buffer.replace(buffer);
0
})
})
.unwrap_or(0);
kernel_data.schedule_upcall(0, (7, status, 0)).ok();
});
});
}
}
// Check to see if we were listening as an I2C slave and should re-enable
// that mode.
if self.listening.get() {
hil::i2c::I2CSlave::enable(self.i2c);
hil::i2c::I2CSlave::listen(self.i2c);
}
}
}
impl<'a, I: hil::i2c::I2CMasterSlave<'a>> hil::i2c::I2CHwSlaveClient
for I2CMasterSlaveDriver<'a, I>
{
fn command_complete(
&self,
buffer: &'static mut [u8],
length: usize,
transmission_type: hil::i2c::SlaveTransmissionType,
) {
// Need to know if read or write
// - on write, copy bytes to app slice and do callback
// then pass buffer back to hw driver
// - on read, just signal upper layer and replace the read buffer
// in this driver
match transmission_type {
hil::i2c::SlaveTransmissionType::Write => {
self.app.map(|app| {
let _ = self.apps.enter(app, |_, kernel_data| {
kernel_data
.get_readwrite_processbuffer(rw_allow::SLAVE_RX)
.and_then(|slave_rx| {
slave_rx.mut_enter(move |app_rx| {
// Check bounds for write length
// Because this (somewhat incorrectly) doesn't report
// back how many bytes were read, the result of mut_map_or
// is ignored. Note that this requires userspace to keep
// track of this information, and if read_len is longer
// than the buffer could lead to array overrun errors in
// userspace. The I2C syscall API should pass back lengths.
// -pal 3/5/21
let buf_len = cmp::min(app_rx.len(), buffer.len());
let read_len = cmp::min(buf_len, length);
for (i, c) in buffer[0..read_len].iter_mut().enumerate() {
app_rx[i].set(*c);
}
self.slave_buffer1.replace(buffer);
0
})
})
.unwrap_or(0);
kernel_data.schedule_upcall(0, (3, length, 0)).ok();
});
});
}
hil::i2c::SlaveTransmissionType::Read => {
self.slave_buffer2.replace(buffer);
// Notify the app that the read finished
self.app.map(|app| {
let _ = self.apps.enter(app, |_, kernel_data| {
kernel_data.schedule_upcall(0, (4, length, 0)).ok();
});
});
}
}
}
fn read_expected(&self) {
// Pass this up to the client. Not much we can do until the application
// has setup a buffer to read from.
self.app.map(|app| {
let _ = self.apps.enter(app, |_, kernel_data| {
// Ask the app to setup a read buffer. The app must call
// command 3 after it has setup the shared read buffer with
// the correct bytes.
kernel_data.schedule_upcall(0, (2, 0, 0)).ok();
});
});
}
fn write_expected(&self) {
// Don't expect this to occur. We will typically have a buffer waiting
// to receive bytes because this module has a buffer and may as well
// just let the hardware layer have it. But, if it does happen
// we can respond.
self.slave_buffer1.take().map(|buffer| {
// TODO verify errors
let _ = hil::i2c::I2CSlave::write_receive(self.i2c, buffer, 255);
});
}
}
impl<'a, I: hil::i2c::I2CMasterSlave<'a>> SyscallDriver for I2CMasterSlaveDriver<'a, I> {
fn command(
&self,
command_num: usize,
data: usize,
_: usize,
process_id: ProcessId,
) -> CommandReturn {
if command_num == 0 {
// Handle unconditional driver existence check.
return CommandReturn::success();
}
// Check if this non-virtualized driver is already in use by
// some (alive) process
let match_or_empty_or_nonexistant = self.app.map_or(true, |current_process| {
self.apps
.enter(current_process, |_, _| current_process == process_id)
.unwrap_or(true)
});
if match_or_empty_or_nonexistant {
self.app.set(process_id);
} else {
return CommandReturn::failure(ErrorCode::NOMEM);
}
let app = process_id;
match command_num {
// Do a write to another I2C device
1 => {
let address = (data & 0xFFFF) as u8;
let len = (data >> 16) & 0xFFFF;
// No need to check error on enter() -- we entered successfully
// above, so grant is allocated, and the app can't disappear
// while we are in the kernel.
let _ = self.apps.enter(app, |_, kernel_data| {
kernel_data
.get_readonly_processbuffer(ro_allow::MASTER_TX)
.and_then(|master_tx| {
master_tx.enter(|app_tx| {
// Because this (somewhat incorrectly) doesn't report
// back how many bytes are being written, the result of mut_map_or
// is ignored. Note that this does not provide useful feedback
// to user space if a write is longer than the buffer.
// The I2C syscall API should pass back lengths.
// -pal 3/5/21
self.master_buffer.take().map(|kernel_tx| {
// Check bounds for write length
let buf_len = cmp::min(app_tx.len(), kernel_tx.len());
let write_len = cmp::min(buf_len, len);
for (i, c) in kernel_tx[0..write_len].iter_mut().enumerate() {
*c = app_tx[i].get();
}
self.master_action.set(MasterAction::Write);
hil::i2c::I2CMaster::enable(self.i2c);
// TODO verify errors
let _ = hil::i2c::I2CMaster::write(
self.i2c, address, kernel_tx, write_len,
);
});
0
})
})
.unwrap_or(0);
});
CommandReturn::success()
}
// Do a read to another I2C device
2 => {
let address = (data & 0xFFFF) as u8;
let len = (data >> 16) & 0xFFFF;
let _ = self.apps.enter(app, |_, kernel_data| {
// Because this (somewhat incorrectly) doesn't report
// back how many bytes are being read, the result of mut_map_or
// is ignored. Note that this does not provide useful feedback
// to user space if a write is longer than the buffer.
// The I2C syscall API should pass back lengths.
// -pal 3/5/21
kernel_data
.get_readwrite_processbuffer(rw_allow::MASTER_RX)
.and_then(|master_rx| {
master_rx.enter(|app_rx| {
self.master_buffer.take().map(|kernel_tx| {
// Check bounds for write length
let buf_len = cmp::min(app_rx.len(), kernel_tx.len());
let read_len = cmp::min(buf_len, len);
for (i, c) in kernel_tx[0..read_len].iter_mut().enumerate() {
*c = app_rx[i].get();
}
self.master_action.set(MasterAction::Read(read_len as u8));
hil::i2c::I2CMaster::enable(self.i2c);
// TODO verify errors
let _ = hil::i2c::I2CMaster::read(
self.i2c, address, kernel_tx, read_len,
);
});
0
})
})
.unwrap_or(0);
});
CommandReturn::success()
}
// Listen for messages to this device as a slave.
3 => {
// We can always handle a write since this module has a buffer.
// .map will handle if we have already done this.
self.slave_buffer1.take().map(|buffer| {
// TODO verify errors
let _ = hil::i2c::I2CSlave::write_receive(self.i2c, buffer, 255);
});
// Actually get things going
hil::i2c::I2CSlave::enable(self.i2c);
hil::i2c::I2CSlave::listen(self.i2c);
// Note that we have enabled listening, so that if we switch
// to Master mode to send a message we can go back to listening.
self.listening.set(true);
CommandReturn::success()
}
// Prepare for a read from another Master by passing what's
// in the shared slice to the lower level I2C hardware driver.
4 => {
let _ = self.apps.enter(app, |_, kernel_data| {
// Because this (somewhat incorrectly) doesn't report
// back how many bytes are being read, the result of mut_map_or
// is ignored. Note that this does not provide useful feedback
// to user space if a write is longer than the buffer.
// The I2C syscall API should pass back lengths.
// -pal 3/5/21
kernel_data
.get_readonly_processbuffer(ro_allow::SLAVE_TX)
.and_then(|slave_tx| {
slave_tx.enter(|app_tx| {
self.slave_buffer2.take().map(|kernel_tx| {
// Check bounds for write length
let len = data;
let buf_len = cmp::min(app_tx.len(), kernel_tx.len());
let read_len = cmp::min(buf_len, len);
for (i, c) in kernel_tx[0..read_len].iter_mut().enumerate() {
*c = app_tx[i].get();
}
// TODO verify errors
let _ = hil::i2c::I2CSlave::read_send(
self.i2c, kernel_tx, read_len,
);
});
0
})
})
.unwrap_or(0);
});
CommandReturn::success()
}
// Stop listening for messages as an I2C slave
5 => {
hil::i2c::I2CSlave::disable(self.i2c);
// We are no longer listening for I2C messages from a different
// master device.
self.listening.set(false);
CommandReturn::success()
}
// Setup this device's slave address.
6 => {
let address = data as u8;
// We do not count the R/W bit as part of the address, so the
// valid range is 0x00-0x7f
if address > 0x7f {
return CommandReturn::failure(ErrorCode::INVAL);
}
// TODO verify errors
let _ = hil::i2c::I2CSlave::set_address(self.i2c, address);
CommandReturn::success()
}
// Perform write-to then read-from a slave device.
// Uses tx buffer for both read and write.
7 => {
let address = (data & 0xFF) as u8;
let read_len = (data >> 8) & 0xFF;
let write_len = (data >> 16) & 0xFF;
let _ = self.apps.enter(app, |_, kernel_data| {
// Because this (somewhat incorrectly) doesn't report
// back how many bytes are being read/read, the result of mut_map_or
// is ignored. Note that this does not provide useful feedback
// to user space if a write is longer than the buffer.
// The I2C syscall API should pass back lengths.
// -pal 3/5/21
let _ = kernel_data
.get_readonly_processbuffer(ro_allow::MASTER_TX)
.and_then(|master_tx| {
master_tx.enter(|app_tx| {
self.master_buffer.take().map(|kernel_tx| {
// Check bounds for write length
let buf_len = cmp::min(app_tx.len(), kernel_tx.len());
let write_len = cmp::min(buf_len, write_len);
let read_len = cmp::min(buf_len, read_len);
app_tx[..write_len].copy_to_slice(&mut kernel_tx[..write_len]);
self.master_action
.set(MasterAction::WriteRead(read_len as u8));
hil::i2c::I2CMaster::enable(self.i2c);
// TODO verify errors
let _ = hil::i2c::I2CMaster::write_read(
self.i2c, address, kernel_tx, write_len, read_len,
);
});
})
});
});
CommandReturn::success()
}
// default
_ => CommandReturn::failure(ErrorCode::NOSUPPORT),
}
}
fn allocate_grant(&self, processid: ProcessId) -> Result<(), kernel::process::Error> {
self.apps.enter(processid, |_, _| {})
}
}