rust-osdev/uart_16550

Minimal support for uart_16550 serial output.

uart_16550's Issues

risc-v Support

Stumbled over this crate while writing a toy OS.

Currently only x86 is supported (via x86_64::...::Port).

Would PR with RISC-V support be accepted?

error[E0599]: no method named `init` found for unit type `()` in the current scope

I tried following the test part of the Rust OSDev Tutorial but when i try using serial_port.init(); I get this error.

error[E0599]: no method named `init` found for unit type `()` in the current scope
--> src/serial.rs:9:21
|
9 | serial_port.init();
| ^^^^ method not found in `()`

I am using uart_16550 version 0.2.0
I don't know if this is the right place.

Implement `Write` on the serial ports so that it can be easily made into a `println!`

please... since I cannot implement Write on your types

might want to update the x86_64 dep

uart_16550/Cargo.toml

Line 12 in 520b9d6

x86_64 = "0.7.3"

x86_64 v0.12.3 No longer works on Nightly.

Error:

error[E0557]: feature has been removed
 --> C:\Users\chknm\.cargo\registry\src\github.com-1ecc6299db9ec823\x86_64-0.12.3\src\lib.rs:9:43
  |
9 | #![cfg_attr(feature = "const_fn", feature(const_in_array_repeat_expressions))]
  |                                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ feature has been removed
  |
  = note: removed due to causing promotable bugs
error: could not compile `x86_64`

An update is required to work.

Suggestion: roll `init` into `new`, test with loopback + scratch pad register, and return `Result` instead of marking `SerialPort` as `unsafe`

I'll preface this by saying that it's very possible that I've totally misunderstood how this all works.

As I understand it from reading https://wiki.osdev.org/Serial_Ports#Port_Addresses, it's possible that not even COM1 may exist, and so it's recommended to always test a port via loopback and the "scratch pad register". There's some example code further down the page that appears to do this:

#define PORT 0x3f8          // COM1
 
static int init_serial() {
   outb(PORT + 1, 0x00);    // Disable all interrupts
   outb(PORT + 3, 0x80);    // Enable DLAB (set baud rate divisor)
   outb(PORT + 0, 0x03);    // Set divisor to 3 (lo byte) 38400 baud
   outb(PORT + 1, 0x00);    //                  (hi byte)
   outb(PORT + 3, 0x03);    // 8 bits, no parity, one stop bit
   outb(PORT + 2, 0xC7);    // Enable FIFO, clear them, with 14-byte threshold
   outb(PORT + 4, 0x0B);    // IRQs enabled, RTS/DSR set
   outb(PORT + 4, 0x1E);    // Set in loopback mode, test the serial chip
   outb(PORT + 0, 0xAE);    // Test serial chip (send byte 0xAE and check if serial returns same byte)
 
   // Check if serial is faulty (i.e: not same byte as sent)
   if(inb(PORT + 0) != 0xAE) {
      return 1;
   }
 
   // If serial is not faulty set it in normal operation mode
   // (not-loopback with IRQs enabled and OUT#1 and OUT#2 bits enabled)
   outb(PORT + 4, 0x0F);
   return 0;
}

I was thinking it might be nice if this crate, rather than marking SerialPort::new as unsafe, instead rolled init into new (I don't see that there would ever be a reason not to call init?), and that it does the loopback + scratch pad register test. new could then return a Result depending on the outcome.

Ways to disable backspace char escaping?

In one of my own projects, I had a case where binary data is transmitted through UART. But later I discovered that the code in this crate silently escapes the backspace character \x08 to \x08\x20\x08, which causes data corruption in my code:

match data {
    8 | 0x7F => {
        wait_for!(self.line_sts().contains(LineStsFlags::OUTPUT_EMPTY));
        self.data.write(8);
        wait_for!(self.line_sts().contains(LineStsFlags::OUTPUT_EMPTY));
        self.data.write(b' ');
        wait_for!(self.line_sts().contains(LineStsFlags::OUTPUT_EMPTY));
        self.data.write(8)
    }
    [...]
}

Maybe this behavior should be clearly described in the documentation, and another method which disables escaping should be added?

Remove `nightly`/`stable` features when Rust 1.61 is released

The const_ptr_offset feature was stabilized in rust-lang/rust#93957. We removed that feature gate from this crate in #22. Right now, we still need the stable and nightly features of this crate to make MmioSerialPort::new a const function on nightly, but on Rust 1.61 this should be supported on stable as well. So we should remove the crate features when 1.61 is released.

Just a question. Why sending 8, space, 8 for a backspace or a delete ascii ctrl char ?

uart_16550/src/mmio.rs

Line 83 in d401ea1

self_data.write(8);

use of unstable library feature 'renamed_spin_loop'

I have tried to add this crate to an empty project with rust nightly.
When trying to build compilation fails with error:
error[E0658]: use of unstable library feature 'renamed_spin_loop'
It also recommends to add the crate attribute #![feature(renamed_spin_loop)]
However, adding this to my crate does nothing.

I have then tried to clone this crate and build it directly.
This causes the same error.
However compilation is successfull after adding the crate attribute to the top of uart_16550's lib.rs.

Is this an error on my end?