VGA Text Mode (zh-CN)

[giscus[bot]]

VGA Text Mode (zh-CN)

VGA 字符模式（VGA text mode）是打印字符到屏幕的一种简单方式。在这篇文章中，为了包装这个模式为一个安全而简单的接口，我们将包装 unsafe 代码到独立的模块。我们还将实现对 Rust 语言格式化宏（formatting macros）的支持。

https://os.phil-opp.com/zh-CN/vga-text-mode/

[CornerOfSkyline]

Spin version in the article used "0.4.9", but the feature "const_fn" has been removed in current rust version. We can change the spin version to "0.9.2" to solve the problem.

[toksdotdev]

Thanks a lot for the article. Was really helpful.

For someone who'll like to use the most recent version of volatile (0.4.4 as at the time of writing), you'll need to implement the Deref and DerefMut trait for ScreenChar.

Something along the lines of:

impl DerefMut for ScreenChar {
    fn deref_mut(&mut self) -> &mut Self::Target {
        self
    }
}

impl Deref for ScreenChar {
    type Target = ScreenChar;

    fn deref(&self) -> &Self::Target {
        self
    }
}

Asides from that, everything in the article pretty much remains the same.

[TisnKu]

Why ascii_code is before color_code while VGA has color code on higher bytes?

Is it because of little endian?

[romatthe]

Since we're using nightly Rust here, is there a reason why we can't use core::ptr::write_volatile and core::ptr::read_volatile here instead of using the volatile crate? Or is the article simply saying it's better to use an ergonomic crate like volatile here instead of directly using unsafe code ourselves? Either one is fine by me, but we're going to need to learn how to built our own safe abstractions in this domain anyway.

[bjmayor]

赞

[llllishuo]

I don't know why this problem occurred
When I run cargo bootimage The error manifests as

error[E0463]: can't find crate for `std`
  |
  = note: the `x86_64-unknown-none` target may not support the standard library
  = note: `std` is required by `os_rust_demo` because it does not declare `#![no_std]`
  = help: consider building the standard library from source with `cargo build -Zbuild-std`

error: cannot find attribute `derive` in this scope
  --> src/vga_buffer.rs:35:3
   |
35 | #[derive(Debug, Clone, Copy, PartialEq, Eq)]
   |   ^^^^^^
   |
help: consider importing this attribute macro
   |
3  + use core::prelude::rust_2024::derive;
   |

in .cargo/config.toml

$ cat .cargo/config.toml
[unstable]
build-std = ["core", "compiler_builtins"]
build-std-features = ["compiler-builtins-mem"]


[build]
target = "x86_64-unknown-none.json"


[target.'cfg(target_os = "none")']
runner = "bootimage runner"

[llllishuo]

I have discovered my problem. I created a new lib.rs. Perhaps this is the reason that caused the no_std to fail

[xuanplus]

Maybe you can try the edition-3, which has a better way to set target and so on.

[phil-opp]

I have discovered my problem. I created a new lib.rs. Perhaps this is the reason that caused the no_std to fail

Yes, that seems likely. Every lib.rs or main.rs file that should be no_std needs the #![no_std] attribute.