mirror of
https://github.com/italicsjenga/gba.git
synced 2024-12-24 11:11:31 +11:00
311 lines
20 KiB
HTML
311 lines
20 KiB
HTML
<!DOCTYPE HTML>
|
|
<html lang="en" class="sidebar-visible no-js">
|
|
<head>
|
|
<!-- Book generated using mdBook -->
|
|
<meta charset="UTF-8">
|
|
<title>No Std - Rust GBA Guide</title>
|
|
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
|
|
<meta name="description" content="">
|
|
<meta name="viewport" content="width=device-width, initial-scale=1">
|
|
<meta name="theme-color" content="#ffffff" />
|
|
|
|
<link rel="shortcut icon" href="../favicon.png">
|
|
<link rel="stylesheet" href="../css/variables.css">
|
|
<link rel="stylesheet" href="../css/general.css">
|
|
<link rel="stylesheet" href="../css/chrome.css">
|
|
<link rel="stylesheet" href="../css/print.css" media="print">
|
|
|
|
<!-- Fonts -->
|
|
<link rel="stylesheet" href="../FontAwesome/css/font-awesome.css">
|
|
<link href="https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800" rel="stylesheet" type="text/css">
|
|
<link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500" rel="stylesheet" type="text/css">
|
|
|
|
<!-- Highlight.js Stylesheets -->
|
|
<link rel="stylesheet" href="../highlight.css">
|
|
<link rel="stylesheet" href="../tomorrow-night.css">
|
|
<link rel="stylesheet" href="../ayu-highlight.css">
|
|
|
|
<!-- Custom theme stylesheets -->
|
|
|
|
|
|
|
|
</head>
|
|
<body class="light">
|
|
<!-- Provide site root to javascript -->
|
|
<script type="text/javascript">var path_to_root = "../";</script>
|
|
|
|
<!-- Work around some values being stored in localStorage wrapped in quotes -->
|
|
<script type="text/javascript">
|
|
try {
|
|
var theme = localStorage.getItem('mdbook-theme');
|
|
var sidebar = localStorage.getItem('mdbook-sidebar');
|
|
|
|
if (theme.startsWith('"') && theme.endsWith('"')) {
|
|
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
|
|
}
|
|
|
|
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
|
|
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
|
|
}
|
|
} catch (e) { }
|
|
</script>
|
|
|
|
<!-- Set the theme before any content is loaded, prevents flash -->
|
|
<script type="text/javascript">
|
|
var theme;
|
|
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
|
|
if (theme === null || theme === undefined) { theme = 'light'; }
|
|
document.body.className = theme;
|
|
document.querySelector('html').className = theme + ' js';
|
|
</script>
|
|
|
|
<!-- Hide / unhide sidebar before it is displayed -->
|
|
<script type="text/javascript">
|
|
var html = document.querySelector('html');
|
|
var sidebar = 'hidden';
|
|
if (document.body.clientWidth >= 1080) {
|
|
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
|
|
sidebar = sidebar || 'visible';
|
|
}
|
|
html.classList.remove('sidebar-visible');
|
|
html.classList.add("sidebar-" + sidebar);
|
|
</script>
|
|
|
|
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
|
|
<ol class="chapter"><li><a href="../00-introduction/00-index.html"><strong aria-hidden="true">1.</strong> Introduction</a></li><li><ol class="section"><li><a href="../00-introduction/01-requirements.html"><strong aria-hidden="true">1.1.</strong> Reader Requirements</a></li><li><a href="../00-introduction/02-goals_and_style.html"><strong aria-hidden="true">1.2.</strong> Book Goals and Style</a></li><li><a href="../00-introduction/03-development-setup.html"><strong aria-hidden="true">1.3.</strong> Development Setup</a></li><li><a href="../00-introduction/04-hello-magic.html"><strong aria-hidden="true">1.4.</strong> Hello, Magic</a></li><li><a href="../00-introduction/05-help_and_resources.html"><strong aria-hidden="true">1.5.</strong> Help and Resources</a></li></ol></li><li><a href="../01-quirks/00-index.html"><strong aria-hidden="true">2.</strong> Quirks</a></li><li><ol class="section"><li><a href="../01-quirks/01-no_std.html" class="active"><strong aria-hidden="true">2.1.</strong> No Std</a></li><li><a href="../01-quirks/02-fixed_only.html"><strong aria-hidden="true">2.2.</strong> Fixed Only</a></li><li><a href="../01-quirks/03-volatile_destination.html"><strong aria-hidden="true">2.3.</strong> Volatile Destination</a></li><li><a href="../01-quirks/04-newtype.html"><strong aria-hidden="true">2.4.</strong> Newtype</a></li><li><a href="../01-quirks/05-const_asserts.html"><strong aria-hidden="true">2.5.</strong> Const Asserts</a></li></ol></li><li><a href="../02-concepts/00-index.html"><strong aria-hidden="true">3.</strong> Concepts</a></li><li><ol class="section"><li><a href="../02-concepts/01-cpu.html"><strong aria-hidden="true">3.1.</strong> CPU</a></li><li><a href="../02-concepts/02-bios.html"><strong aria-hidden="true">3.2.</strong> BIOS</a></li><li><a href="../02-concepts/03-wram.html"><strong aria-hidden="true">3.3.</strong> Work RAM</a></li><li><a href="../02-concepts/04-io-registers.html"><strong aria-hidden="true">3.4.</strong> IO Registers</a></li><li><a href="../02-concepts/05-palram.html"><strong aria-hidden="true">3.5.</strong> Palette RAM</a></li><li><a href="../02-concepts/06-vram.html"><strong aria-hidden="true">3.6.</strong> Video RAM</a></li><li><a href="../02-concepts/07-oam.html"><strong aria-hidden="true">3.7.</strong> Object Attribute Memory</a></li><li><a href="../02-concepts/08-rom.html"><strong aria-hidden="true">3.8.</strong> Game Pak ROM / Flash ROM</a></li><li><a href="../02-concepts/09-sram.html"><strong aria-hidden="true">3.9.</strong> Save RAM</a></li></ol></li><li><a href="../03-video/00-index.html"><strong aria-hidden="true">4.</strong> Video</a></li><li><ol class="section"><li><a href="../03-video/01-rgb15.html"><strong aria-hidden="true">4.1.</strong> RBG15 Color</a></li><li><a href="../03-video/TODO.html"><strong aria-hidden="true">4.2.</strong> TODO</a></li></ol></li><li><a href="../04-non-video/00-index.html"><strong aria-hidden="true">5.</strong> Non-Video</a></li><li><ol class="section"><li><a href="../04-non-video/01-buttons.html"><strong aria-hidden="true">5.1.</strong> Buttons</a></li><li><a href="../04-non-video/02-timers.html"><strong aria-hidden="true">5.2.</strong> Timers</a></li><li><a href="../04-non-video/03-dma.html"><strong aria-hidden="true">5.3.</strong> Direct Memory Access</a></li><li><a href="../04-non-video/04-sound.html"><strong aria-hidden="true">5.4.</strong> Sound</a></li><li><a href="../04-non-video/05-interrupts.html"><strong aria-hidden="true">5.5.</strong> Interrupts</a></li><li><a href="../04-non-video/06-link_cable.html"><strong aria-hidden="true">5.6.</strong> Link Cable</a></li><li><a href="../04-non-video/07-game_pak.html"><strong aria-hidden="true">5.7.</strong> Game Pak</a></li></ol></li><li><a href="../05-examples/00-index.html"><strong aria-hidden="true">6.</strong> Examples</a></li></ol>
|
|
</nav>
|
|
|
|
<div id="page-wrapper" class="page-wrapper">
|
|
|
|
<div class="page">
|
|
|
|
<div id="menu-bar" class="menu-bar">
|
|
<div id="menu-bar-sticky-container">
|
|
<div class="left-buttons">
|
|
<button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
|
|
<i class="fa fa-bars"></i>
|
|
</button>
|
|
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
|
|
<i class="fa fa-paint-brush"></i>
|
|
</button>
|
|
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
|
|
<li role="none"><button role="menuitem" class="theme" id="light">Light <span class="default">(default)</span></button></li>
|
|
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
|
|
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
|
|
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
|
|
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
|
|
</ul>
|
|
|
|
<button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
|
|
<i class="fa fa-search"></i>
|
|
</button>
|
|
|
|
</div>
|
|
|
|
<h1 class="menu-title">Rust GBA Guide</h1>
|
|
|
|
<div class="right-buttons">
|
|
<a href="../print.html" title="Print this book" aria-label="Print this book">
|
|
<i id="print-button" class="fa fa-print"></i>
|
|
</a>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
|
|
|
|
<div id="search-wrapper" class="hidden">
|
|
<form id="searchbar-outer" class="searchbar-outer">
|
|
<input type="search" name="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
|
|
</form>
|
|
<div id="searchresults-outer" class="searchresults-outer hidden">
|
|
<div id="searchresults-header" class="searchresults-header"></div>
|
|
<ul id="searchresults">
|
|
</ul>
|
|
</div>
|
|
</div>
|
|
|
|
|
|
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
|
|
<script type="text/javascript">
|
|
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
|
|
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
|
|
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
|
|
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
|
|
});
|
|
</script>
|
|
|
|
<div id="content" class="content">
|
|
<main>
|
|
<a class="header" href="#no-std" id="no-std"><h1>No Std</h1></a>
|
|
<p>First up, as you already saw in the <code>hello_magic</code> code, we have to use the
|
|
<code>#![no_std]</code> outer attribute on our program when we target the GBA. You can find
|
|
some info about <code>no_std</code> in two official sources:</p>
|
|
<ul>
|
|
<li><a href="https://doc.rust-lang.org/unstable-book/language-features/lang-items.html#writing-an-executable-without-stdlib">unstable
|
|
book section</a></li>
|
|
<li><a href="https://rust-embedded.github.io/book/intro/no-std.html?highlight=no_std#a--no_std--rust-environment">embedded
|
|
book section</a></li>
|
|
</ul>
|
|
<p>The unstable book is borderline useless here because it's describing too many
|
|
things in too many words. The embedded book is much better, but still fairly
|
|
terse.</p>
|
|
<a class="header" href="#bare-metal" id="bare-metal"><h2>Bare Metal</h2></a>
|
|
<p>The GBA falls under what the Embedded Book calls "Bare Metal Environments".
|
|
Basically, the machine powers on and immediately begins executing some ASM code.
|
|
Our ASM startup was provided by <code>Ketsuban</code> (check the <code>crt0.s</code> file). We'll go
|
|
over <em>how</em> it works much later on, for now it's enough to know that it does
|
|
work, and eventually control passes into Rust code.</p>
|
|
<p>On the rust code side of things, we determine our starting point with the
|
|
<code>#[start]</code> attribute on our <code>main</code> function. The <code>main</code> function also has a
|
|
specific type signature that's different from the usual <code>main</code> that you'd see in
|
|
Rust. I'd tell you to read the unstable-book entry on <code>#[start]</code> but they
|
|
<a href="https://doc.rust-lang.org/unstable-book/language-features/start.html">literally</a>
|
|
just tell you to look at the <a href="https://github.com/rust-lang/rust/issues/29633">tracking issue for
|
|
it</a> instead, and that's not very
|
|
helpful either. Basically it just <em>has</em> to be declared the way it is, even
|
|
though there's nothing passing in the arguments and there's no place that the
|
|
return value will go. The compiler won't accept it any other way.</p>
|
|
<a class="header" href="#no-standard-library" id="no-standard-library"><h2>No Standard Library</h2></a>
|
|
<p>The Embedded Book tells us that we can't use the standard library, but we get
|
|
access to something called "libcore", which sounds kinda funny. What they're
|
|
talking about is just <a href="https://doc.rust-lang.org/core/index.html">the core
|
|
crate</a>, which is called <code>libcore</code>
|
|
within the rust repository for historical reasons.</p>
|
|
<p>The <code>core</code> crate is actually still a really big portion of Rust. The standard
|
|
library doesn't actually hold too much code (relatively speaking), instead it
|
|
just takes code form other crates and then re-exports it in an organized way. So
|
|
with just <code>core</code> instead of <code>std</code>, what are we missing?</p>
|
|
<p>In no particular order:</p>
|
|
<ul>
|
|
<li>Allocation</li>
|
|
<li>Clock</li>
|
|
<li>Network</li>
|
|
<li>File System</li>
|
|
</ul>
|
|
<p>The allocation system and all the types that you can use if you have a global
|
|
allocator are neatly packaged up in the
|
|
<a href="https://doc.rust-lang.org/alloc/index.html">alloc</a> crate. The rest isn't as
|
|
nicely organized.</p>
|
|
<p>It's <em>possible</em> to implement a fair portion of the entire standard library
|
|
within a GBA context and make the rest just panic if you try to use it. However,
|
|
do you really need all that? Eh... probably not?</p>
|
|
<ul>
|
|
<li>We don't need a file system, because all of our data is just sitting there in
|
|
the ROM for us to use. When programming we can organize our <code>const</code> data into
|
|
modules and such to keep it organized, but once the game is compiled it's just
|
|
one huge flat address space. TODO: Parasyte says that a FS can be handy even
|
|
if it's all just ReadOnly, so we'll eventually talk about how you might set up
|
|
such a thing I guess, since we'll already be talking about replacements for
|
|
three of the other four things we "lost". Maybe we'll make Parasyte write that
|
|
section.</li>
|
|
<li>Networking, well, the GBA has a Link Cable you can use to communicate with
|
|
another GBA, but it's not really like a unix socket with TCP, so the standard
|
|
Rust networking isn't a very good match.</li>
|
|
<li>Clock is actually two different things at once. One is the ability to store
|
|
the time long term, which is a bit of hardware that some gamepaks have in them
|
|
(eg: pokemon ruby/sapphire/emerald). The GBA itself can't keep time while
|
|
power is off. However, the second part is just tracking time moment to moment,
|
|
which the GBA can totally do. We'll see how to access the timers soon enough.</li>
|
|
</ul>
|
|
<p>Which just leaves us with allocation. Do we need an allocator? Depends on your
|
|
game. For demos and small games you probably don't need one. For bigger games
|
|
you'll maybe want to get an allocator going eventually. It's in some sense a
|
|
crutch, but it's a very useful one.</p>
|
|
<p>So I promise that at some point we'll cover how to get an allocator going.
|
|
Either a Rust Global Allocator (if practical), which would allow for a lot of
|
|
the standard library types to be used "for free" once it was set up, or just a
|
|
custom allocator that's GBA specific if Rust's global allocator style isn't a
|
|
good fit for the GBA (I honestly haven't looked into it).</p>
|
|
<a class="header" href="#bare-metal-panic" id="bare-metal-panic"><h2>Bare Metal Panic</h2></a>
|
|
<p>TODO: expand this</p>
|
|
<ul>
|
|
<li>Write <code>0xC0DE</code> to <code>0x4fff780</code> (<code>u16</code>) to enable mGBA logging. Write any other
|
|
value to disable it.</li>
|
|
<li>Read <code>0x4fff780</code> (<code>u16</code>) to check mGBA logging status.
|
|
<ul>
|
|
<li>You get <code>0x1DEA</code> if debugging is active.</li>
|
|
<li>Otherwise you get standard open bus nonsense values.</li>
|
|
</ul>
|
|
</li>
|
|
<li>Write your message into the virtual <code>[u8; 255]</code> array starting at <code>0x4fff600</code>.
|
|
mGBA will interpret these bytes as a CString value.</li>
|
|
<li>Write <code>0x100</code> PLUS the message level to <code>0x4fff700</code> (<code>u16</code>) when you're ready
|
|
to send a message line:
|
|
<ul>
|
|
<li>0: Fatal (halts execution with a popup)</li>
|
|
<li>1: Error</li>
|
|
<li>2: Warning</li>
|
|
<li>3: Info</li>
|
|
<li>4: Debug</li>
|
|
</ul>
|
|
</li>
|
|
<li>Sending the message also automatically zeroes the output buffer.</li>
|
|
<li>View the output within the "Tools" menu, "View Logs...". Note that the Fatal
|
|
message, if any doesn't get logged.</li>
|
|
</ul>
|
|
<p>TODO: this will probably fail without a <code>__clzsi2</code> implementation, which is a
|
|
good seg for the next section</p>
|
|
<a class="header" href="#llvm-intrinsics" id="llvm-intrinsics"><h2>LLVM Intrinsics</h2></a>
|
|
<p>TODO: explain that we'll occasionally have to provide some intrinsics.</p>
|
|
|
|
</main>
|
|
|
|
<nav class="nav-wrapper" aria-label="Page navigation">
|
|
<!-- Mobile navigation buttons -->
|
|
|
|
<a rel="prev" href="../01-quirks/00-index.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
|
<i class="fa fa-angle-left"></i>
|
|
</a>
|
|
|
|
|
|
|
|
<a rel="next" href="../01-quirks/02-fixed_only.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
|
<i class="fa fa-angle-right"></i>
|
|
</a>
|
|
|
|
|
|
<div style="clear: both"></div>
|
|
</nav>
|
|
</div>
|
|
</div>
|
|
|
|
<nav class="nav-wide-wrapper" aria-label="Page navigation">
|
|
|
|
<a href="../01-quirks/00-index.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
|
|
<i class="fa fa-angle-left"></i>
|
|
</a>
|
|
|
|
|
|
|
|
<a href="../01-quirks/02-fixed_only.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
|
|
<i class="fa fa-angle-right"></i>
|
|
</a>
|
|
|
|
</nav>
|
|
|
|
</div>
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
<script src="../elasticlunr.min.js" type="text/javascript" charset="utf-8"></script>
|
|
<script src="../mark.min.js" type="text/javascript" charset="utf-8"></script>
|
|
<script src="../searcher.js" type="text/javascript" charset="utf-8"></script>
|
|
|
|
|
|
<script src="../clipboard.min.js" type="text/javascript" charset="utf-8"></script>
|
|
<script src="../highlight.js" type="text/javascript" charset="utf-8"></script>
|
|
<script src="../book.js" type="text/javascript" charset="utf-8"></script>
|
|
|
|
<!-- Custom JS scripts -->
|
|
|
|
|
|
|
|
|
|
</body>
|
|
</html>
|