android_swrast: Publish note

author: Lucas Fryzek <lucas.fryzek@fryzekconcepts.com> 2024-07-02 08:49:23 +0100
committer: Lucas Fryzek <lucas.fryzek@fryzekconcepts.com> 2024-07-02 08:49:23 +0100
commit: 56b2c6263189f5783aad0cd39aaf174088e04670 (patch)
tree: 1ff25ac05c3dc810c9387a476dc0035b667a175d /html/notes
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+    <title>Software Rendering and Android</title>
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+<div class="page-title-header-container">
+    <h1 class="page-title-header">Software Rendering and Android</h1>
+        <div class="page-info-container">
+                    <div class="plant-status">
+                    <img src="/assets/evergreen.svg">
+                    <div class="plant-status-text">
+                    <p>evergreen</p>
+                    </div>
+                    </div>
+                <div class="page-info-date-container">
+            <p class="page-info-date">Published: 2024-06-27</p>
+            <p class="page-info-date">Last Edited: 2024-06-27</p>
+        </div>
+    </div>
+    </div>
+<div class="note-divider"></div>
+<div class="main-container">
+    <div class="note-body">
+<p>My current project at Igalia has had me working on Mesa’s software
+renderers, llvmpipe and lavapipe. I’ve been working to get them running
+on Android, and I wanted to document the progress I’ve made, the
+challenges I’ve faced, and talk a little bit about the development
+process for a project like this. My work is not totally merged into
+upstream mesa yet, but you can see the MRs I made here:</p>
+<ul>
+<li><a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29344">MR
+!29344</a></li>
+<li><a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29785">MR
+!29785</a></li>
+<li><a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27805">MR
+!27805</a></li>
+<li><a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28735">MR
+!28735</a></li>
+</ul>
+<h2 id="setting-up-an-android-development-environment">Setting up an
+Android development environment</h2>
+<p>Getting system level software to build and run on Android is
+unfortunately not straightforward. Since we are doing software rendering
+we don’t need a physical device and instead we can make use of the
+Android emulator, and if you didn’t know Android has two emulators, the
+common one most people use is “goldfish” and the other lesser known is
+“cuttlefish”. For this project I did my work on the cuttlefish emulator
+as its meant for testing the Android OS itself instead of just Android
+apps and is more reflective of real hardware. The cuttlefish emulator
+takes a little bit more work to setup, and I’ve found that it only works
+properly in Debian based linux distros. I run Fedora, so I had to run
+the emulator in a debian VM.</p>
+<p>Thankfully Google has good instructions for building and running
+cuttlefish, which you can find <a
+href="https://source.android.com/docs/devices/cuttlefish/get-started">here</a>.
+The instructions show you how to setup the emulator using nightly build
+images from Google. We’ll also need to setup our own Android OS images
+so after we’ve confirmed we can run the emulator, we need to start
+looking at building AOSP.</p>
+<p>For building our own AOSP image, we can also follow the instructions
+from Google <a
+href="https://source.android.com/docs/setup/build/building">here</a>.
+For the target we’ll want
+<code>aosp_cf_x86_64_phone-trunk_staging-eng</code>. At this point it’s
+a good idea to verify that you can build the image, which you can do by
+following the rest of the instructions on the page. Building AOSP from
+source does take a while though, so prepare to wait potentially an
+entire day for the image to build. Also if you get errors complaining
+that you’re out of memory, you can try to reduce the number of parallel
+builds. Google officially recommends to have 64GB of RAM, and I only had
+32GB so some packages had to be built with the parallel builds set to 1
+so I wouldn’t run out of RAM.</p>
+<p>For running this custom-built image on Cuttlefish, you can just copy
+all the <code>*.img</code> files from
+<code>out/target/product/vsoc_x86_64/</code> to the root cuttlefish
+directory, and then launch cuttlefish. If everything worked successfully
+you should be able to see your custom built AOSP image running in the
+cuttlefish webui.</p>
+<h2 id="building-mesa-targeting-android">Building Mesa targeting
+Android</h2>
+<p>Working from the changes in MR <a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29344">!29344</a>
+building llvmpipe or lavapipe targeting Android should just work™️. To
+get to that stage required a few changes. First llvmpipe actually
+already had some support on Android, as long as it was running on a
+device that supports a DRM display driver. In that case it could use the
+<code>dri</code> window system integration which already works on
+Android. I wanted to get llvmpipe (and lavapipe) running without dri, so
+I had to add support for Android in the <code>drisw</code> window system
+integration.</p>
+<p>To support Android in <code>drisw</code>, this mainly meant adding
+support for importing dmabuf as framebuffers. The Android windowing
+system will provide us with a “gralloc” buffer which inside has a dmabuf
+fd that represents the framebuffer. Adding support for importing dmabufs
+in drisw means we can import and begin drawing to these frame buffers.
+Most the changes to support that can be found in <a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/blob/9705df53408777d493eab19e5a58c432c1e75acb/src/gallium/frontends/dri/drisw.c#L405"><code>drisw_allocate_textures</code></a>
+and the underlying changes to llvmpipe to support importing dmabufs in
+MR <a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27805">!27805</a>.
+The EGL Android platform code also needed some changes to use the
+<code>drisw</code> window system code. Previously this code would only
+work with true dri drivers, but with some small tweaks it was possible
+to get to have it initialize the drisw window system and then using it
+for rendering if no hardware devices are available.</p>
+<p>For lavapipe the changes were a lot simpler. The Android Vulkan
+loader requires your driver to have <code>HAL_MODULE_INFO_SYM</code>
+symbol in the binary, so that got created and populated correctly,
+following other Vulkan drivers in Mesa like turnip. Then the image
+creation code had to be modified to support the
+<code>VK_ANDROID_native_buffer</code> extension which allows the Android
+Vulkan loader to create images using Android native buffer handles.
+Under the hood this means getting the dmabuf fd from the native buffer
+handle. Thankfully mesa already has some common code to handle this, so
+I could just use that. Some other small changes were also necessary to
+address crashes and other failures that came up during testing.</p>
+<p>With the changes out of of the way we can now start building Mesa on
+Android. For this project I had to update the Android documentation for
+Mesa to include steps for building LLVM for Android since the version
+Google ships with the NDK is missing libraries that llvmpipe/lavapipe
+need to function. You can see the updated documentation <a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/blob/9705df53408777d493eab19e5a58c432c1e75acb/docs/drivers/llvmpipe.rst">here</a>
+and <a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/blob/9705df53408777d493eab19e5a58c432c1e75acb/docs/android.rst">here</a>.
+After sorting out LLVM, building llvmpipe/lavapipe is the same as
+building any other Mesa driver for Android: we setup a cross file to
+tell meson how to cross compile and then we run meson. At this point you
+could manual modify the Android image and copy these files to the vm,
+but I also wanted to support building a new AOSP image directly
+including the driver. In order to do that you also have to rename the
+driver binaries to match Android’s naming convention, and make sure
+SO_NAME matches as well. If you check out <a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/blob/9705df53408777d493eab19e5a58c432c1e75acb/docs/android.rst?plain=1#L183">this</a>
+section of the documentation I wrote, it covers how to do that.</p>
+<p>If you followed all of that you should have built an version of
+llvmpipe and lavapipe that you can run on Android’s cuttlefish
+emulator.</p>
+<figure>
+<img src="/assets/2024-06-27-android-swrast/lavapipe.png"
+alt="Android running lavapipe" />
+<figcaption aria-hidden="true">Android running lavapipe</figcaption>
+</figure>
+<h2 id="references">References</h2>
+<ul>
+<li><a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29344"
+class="uri">https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/29344</a>
+<ul>
+<li>Main MR with Android changes</li>
+</ul></li>
+<li><a
+href="https://source.android.com/docs/devices/cuttlefish/get-started"
+class="uri">https://source.android.com/docs/devices/cuttlefish/get-started</a>
+<ul>
+<li>Google’s official guide for getting started with the Cuttlefish
+emulator</li>
+</ul></li>
+<li><a href="https://source.android.com/docs/setup/build/building"
+class="uri">https://source.android.com/docs/setup/build/building</a>
+<ul>
+<li>Google’s official guide for building AOSP images</li>
+</ul></li>
+<li><a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/blob/9705df53408777d493eab19e5a58c432c1e75acb/docs/drivers/llvmpipe.rst"
+class="uri">https://gitlab.freedesktop.org/mesa/mesa/-/blob/9705df53408777d493eab19e5a58c432c1e75acb/docs/drivers/llvmpipe.rst</a>
+<ul>
+<li>My updated documentation in MR for llvmpipe</li>
+</ul></li>
+<li><a
+href="https://gitlab.freedesktop.org/mesa/mesa/-/blob/9705df53408777d493eab19e5a58c432c1e75acb/docs/android.rst"
+class="uri">https://gitlab.freedesktop.org/mesa/mesa/-/blob/9705df53408777d493eab19e5a58c432c1e75acb/docs/android.rst</a>
+<ul>
+<li>My updated documentation in MR for Android integration in mesa</li>
+</ul></li>
+</ul>
+    </div>
+</div>    </main>
+</body>
+</html>
author	Lucas Fryzek <lucas.fryzek@fryzekconcepts.com>	2024-07-02 08:49:23 +0100
committer	Lucas Fryzek <lucas.fryzek@fryzekconcepts.com>	2024-07-02 08:49:23 +0100
commit	56b2c6263189f5783aad0cd39aaf174088e04670 (patch)
tree	1ff25ac05c3dc810c9387a476dc0035b667a175d /html/notes
parent	4487b7797f5a601ad68c8e81d5c7714f46abe0f8 (diff)