Create a DRM driver for VGA video cards
Yes, those VGA video cards. The goal of this project is to implement a DRM graphics driver for such devices. While actual hardware is hard to obtain or even run today, qemu emulates VGA output.
VGA has a number of limitations, which make this project interesting.
- There are only 640x480 pixels (or less) on the screen. That resolution is also a soft lower limit imposed by DRM. It's mostly a problem for desktop environments though.
- Desktop environments assume 16 million colors, but there are only 16 colors with VGA. VGA's 256 color palette is not available at 640x480. We can choose those 16 colors freely. The interesting part is how to choose them. We have to build a palette for the displayed frame and map each color to one of the palette's 16 entries. This is called dithering, and VGA's limitations are a good opportunity to learn about dithering algorithms.
- VGA has an interesting memory layout. Most graphics devices use linear framebuffers, which store the pixels byte by byte. VGA uses 4 bitplanes instead. Plane 0 holds all bits 0 of all pixels. Plane 1 holds all bits 1 of all pixels, and so on.
The driver will probably not be useful to many people. But, if finished, it can serve as test environment for low-level hardware. There's some interest in supporting old Amiga and Atari framebuffers in DRM. Those systems have similar limitations as VGA, but are harder to obtain and test with. With qemu, the VGA driver could fill this gap.
Apart from the Wikipedia entry, good resources on VGA are at osdev.net and FreeVGA
This project is part of:
Hack Week 22 Hack Week 24
Activity
Comments
-
almost 2 years ago by tdz | Reply
I have pushed a skeleton driver to Gitlab. The does not display anything yet, but binds to a provided VGA device. The rsp kernel config for i586 is here.
I use 32-bit Tumbleweed on qemu as testing environment. Here are some short setup instructions.
- Download TW for 32-bit and install in a qemu guest
- There are various emulated graphics devices available with qemu's 32-bit emulation. I use virtio, but anything with VGA should work
- On the installed system, open /etc/default/grub and set 'GRUB_TERMINAL=console' to enable textmode. Also append 'console=ttyS0,115200n8' to 'GRUB_CMDLINE_LINUX_DEFAULT' to enable serial-console output.
- Recreate grub's config with ' sudo grub2-mkconfig -o /boot/grub2/grub.cfg'. These steps will set grub to VGA text mode.
- Build and install the provided kernel. I use 'make O=build-i586/' and then again with module_install and install to get it installed. This requires kernel development tools.
- After a reboot, grub should start in text mode. The development kernel should load the vgadrm driver. It does not display anything. If you switch to the serial console and login, 'dmesg | grep drm' should mention vgadrm.
-
almost 2 years ago by tdz | Reply
Day 1: I started with the skeleton driver that binds to the VGA device without doing proper output. I added blitting code to copy the framebuffer data into the video memory. The driver also installs a default palette on each pageflip. The screen now turns dark, but at least it's obvious that something changed. Updating the video memory is somewhat complicated due to VGA's awkward memory layout and a number of register settings that modify the written framebuffer data.
See https://gitlab.suse.de/tzimmermann/linux/-/commits/vgadrm-day1.
-
-
almost 2 years ago by tdz | Reply
Day 2: I've been fixing register settings for the whole day. The driver is still not functional, but there's at least noise displayed on the screen. The existing material at FreeVGA and osdev.net has been extremely helpful.
See https://gitlab.suse.de/tzimmermann/linux/-/tree/vgadrm-day2.
-
almost 2 years ago by tdz | Reply
Day 3: I only did register debugging today, as I still don't see an image on the screen. VGA has plenty of settings for text mode; plus compatibility with the even older EGA and CGA cards. I guess those could interfere or I'm simply missing something trivial. The qemu emulator doesn't seems to tell me about possible problems. So I'm going to set up a regular BIOS-based PC to test the driver. Connecting a monitor should give a signal and a video mode. If the signal is there, the problem is in the screen update; if not it's in the mode setting.
See https://gitlab.suse.de/tzimmermann/linux/-/tree/vgadrm-day3.
-
-
almost 2 years ago by tdz | Reply
Day 4: I stepped through my commits and made them into smaller pieces until I found the reason why the screen remained dark. It turns out that it's necessary to activate the palette after filling it with colors. The bit the to that is non-intuitively hidden in the attribute controller's index register, which also serve as a data register. The VGA device's interface is often like this and small errors can quickly backfire.
So there's still the noise on the screen, but with repeating patterns. It looks like the final problem is in the way the VGA chips reads from video memory.
See https://gitlab.suse.de/tzimmermann/linux/-/tree/vgadrm-day4.
-
almost 2 years ago by tdz | Reply
Day 5: Today I finally got a working output on the screen! Upon boot, the kernel console is being displayed and it is possible to log in and use the command line. The screen flickers, has a few artifacts and sometimes the colors are off, but it mostly works. I assume that the remaining problems come from many little issue within the kernel's DRM framework. The helpers for color-format conversion and blitting are not prepared to handle 16-color palette modes. So a few fixes might be required. Nevertheless, the display output is there and I count this hackweek project as a success. If I find the time to fix the remaining bugs, I'll send the driver to upstream for inclusion in the official Linux kernel.
See https://gitlab.suse.de/tzimmermann/linux/-/tree/vgadrm-day5.
Similar Projects
Create DRM drivers for VESA and EFI framebuffers by tdz
Description
We already have simpledrm for firmware framebuffers. But the driver is originally for ARM boards, not PCs. It is already overloaded with code to support both use cases. At the same time it is missing possible features for VESA and EFI, such as palette modes or EDID support. We should have DRM drivers for VESA and EFI interfaces. The infrastructure exists already and initial drivers can be forked from simpledrm.
Goals
- Initially, a bare driver for VESA or EFI should be created. It can take functionality from simpledrm.
- Then we can begin to add additional features. The boot loader can provide EDID data. With VGA hardware, VESA can support paletted modes or color management. Example code exists in vesafb.
New openSUSE-welcome by lkocman
Project Description
Let's revisit our existing openSUSE welcome app.
My goal was to show Leap 16 in a new coat. Welcome app adds to the first time use experience. We've recently added donation button to our existing welcome.
Some things that I recently wanted to address were EOL and possibly upgrade notification.
I've already done some experiments with mint welcome app, but not sure if it's better than the existing one.
There is also a PR to rework existing app https://github.com/openSUSE/openSUSE-welcome/pull/36 (this should be considered as an option too)
Goal for this Hackweek
New welcome app, possibly with EOL notification for Leap.
1) Welcome application(s) with (rebrand changes) maintained under github.com/openSUSE
2) Application is submitted to openSUSE:Factory && openSUSE:Leap:16.0
3) Updated needles in openQA (probably post hackweek)
Resources
Reddit discussion about the best welcome app out there.
Github repo for the current welcome app.
Finish gfxprim application multiplexor (window manager) by metan
Project Description
I've implemented drivers for a few e-ink displays during the last hackweek and made sure that gfxprim widgets run nicely on e-ink as well. The missing piece to have a portable e-ink computer/reader/music player/... is a application that can switch between currently running applications and that can start new applications as well. Half of the solution is ready, there is a proxy gfxprim backend where applications render into a piece of a shared memory and input events (e.g. keyboard, mouse) can be multiplexed. What is missing is an interface (possibly touchscreen friendly as well) to make it user friendly.
Goal for this Hackweek
Make nekowm usable "window manager".
Resources
Create DRM drivers for VESA and EFI framebuffers by tdz
Description
We already have simpledrm for firmware framebuffers. But the driver is originally for ARM boards, not PCs. It is already overloaded with code to support both use cases. At the same time it is missing possible features for VESA and EFI, such as palette modes or EDID support. We should have DRM drivers for VESA and EFI interfaces. The infrastructure exists already and initial drivers can be forked from simpledrm.
Goals
- Initially, a bare driver for VESA or EFI should be created. It can take functionality from simpledrm.
- Then we can begin to add additional features. The boot loader can provide EDID data. With VGA hardware, VESA can support paletted modes or color management. Example code exists in vesafb.
Linux on Cavium CN23XX cards by tsbogend
Before Cavium switched to ARM64 CPUs they developed quite powerful MIPS based SOCs. The current upstream Linux kernel already supports some Octeon SOCs, but not the latest versions. Goal of this Hack Week project is to use the latest Cavium SDK to update the Linux kernel code to let it running on CN23XX network cards.
Contributing to Linux Kernel security by pperego
Description
A couple of weeks ago, I found this blog post by Gustavo Silva, a Linux Kernel contributor.
I always strived to start again into hacking the Linux Kernel, so I asked Coverity scan dashboard access and I want to contribute to Linux Kernel by fixing some minor issues.
I want also to create a Linux Kernel fuzzing lab using qemu and syzkaller
Goals
- Fix at least 2 security bugs
- Create the fuzzing lab and having it running
The story so far
- Day 1: setting up a virtual machine for kernel development using Tumbleweed. Reading a lot of documentation, taking confidence with Coverity dashboard and with procedures to submit a kernel patch
- Day 2: I read really a lot of documentation and I triaged some findings on Coverity SAST dashboard. I have to confirm that SAST tool are great false positives generator, even for low hanging fruits.
- Day 3: Working on trivial changes after I read this blog post:
https://www.toblux.com/posts/2024/02/linux-kernel-patches.html. I have to take confidence
with the patch preparation and submit process yet.
- First trivial patch sent: using strtruefalse() macro instead of hard-coded strings in a staging driver for a lcd display
- Fix for a dereference before null check issue discovered by Coverity (CID 1601566) https://scan7.scan.coverity.com/#/project-view/52110/11354?selectedIssue=1601566
- Day 4: Triaging more issues found by Coverity.
- The patch for CID 1601566 was refused. The check against the NULL pointer was pointless so I prepared a version 2 of the patch removing the check.
- Fixed another dereference before NULL check in iwlmvmparsewowlaninfo_notif() routine (CID 1601547). This one was already submitted by another kernel hacker :(
- Day 5: Wrapping up. I had to do some minor rework on patch for CID 1601566. I found a stalker bothering me in private emails and people I interacted with me, advised he is a well known bothering person. Markus Elfring for the record.
Wrapping up: being back doing kernel hacking is amazing and I don't want to stop it. My battery pack is completely drained but changing the scope gave me a great twist and I really want to feel this energy not doing a single task for months.
I failed in setting up a fuzzing lab but I was too optimistic for the patch submission process.
The patches
Create DRM drivers for VESA and EFI framebuffers by tdz
Description
We already have simpledrm for firmware framebuffers. But the driver is originally for ARM boards, not PCs. It is already overloaded with code to support both use cases. At the same time it is missing possible features for VESA and EFI, such as palette modes or EDID support. We should have DRM drivers for VESA and EFI interfaces. The infrastructure exists already and initial drivers can be forked from simpledrm.
Goals
- Initially, a bare driver for VESA or EFI should be created. It can take functionality from simpledrm.
- Then we can begin to add additional features. The boot loader can provide EDID data. With VGA hardware, VESA can support paletted modes or color management. Example code exists in vesafb.
FizzBuzz OS by mssola
Project Description
FizzBuzz OS (or just fbos) is an idea I've had in order to better grasp the fundamentals of the low level of a RISC-V machine. In practice, I'd like to build a small Operating System kernel that is able to launch three processes: one that simply prints "Fizz", another that prints "Buzz", and the third which prints "FizzBuzz". These processes are unaware of each other and it's up to the kernel to schedule them by using the timer interrupts as given on openSBI (fizz on % 3 seconds, buzz on % 5 seconds, and fizzbuzz on % 15 seconds).
This kernel provides just one system call, write, which allows any program to pass the string to be written into stdout.
This project is free software and you can find it here.
Goal for this Hackweek
- Better understand the RISC-V SBI interface.
- Better understand RISC-V in privileged mode.
- Have fun.
Resources
Results
The project was a resounding success 
Lots of learning, and the initial target was met.
Modularization and Modernization of cifs.ko for Enhanced SMB Protocol Support by hcarvalho
Creator:
Enzo Matsumiya ematsumiya@suse.de @ SUSE Samba team
Members:
Henrique Carvalho henrique.carvalho@suse.com @ SUSE Samba team
Description
Split cifs.ko in 2 separate modules; one for SMB 1.0 and 2.0.x, and another for SMB 2.1, 3.0, and 3.1.1.
Goals
Primary
Start phasing out/deprecation of older SMB versions
Secondary
- Clean up of the code (with focus on the newer versions)
- Update cifs-utils
- Update documentation
- Improve backport workflow (see below)
Technical details
Ideas for the implementation.
- fs/smb/client/{old,new}.c to generate the respective modules
- Maybe don't create separate folders? (re-evaluate as things progresses!)
- Remove server->{ops,vals} if possible
- Clean up fs_context.* -- merge duplicate options into one, handle them in userspace utils
- Reduce code in smb2pdu.c -- tons of functions with very similar init/setup -> send/recv -> handle/free flow
- Restructure multichannel
- Treat initial connection as "channel 0" regardless of multichannel enabled/negotiated status, proceed with extra channels accordingly
- Extra channel just point to "channel 0" as the primary server, no need to allocate an extra TCPServerInfo for each one
- Authentication mechanisms
- Modernize algorithms (references: himmelblau, IAKERB/Local KDC, SCRAM, oauth2 (Azure), etc.
Create DRM drivers for VESA and EFI framebuffers by tdz
Description
We already have simpledrm for firmware framebuffers. But the driver is originally for ARM boards, not PCs. It is already overloaded with code to support both use cases. At the same time it is missing possible features for VESA and EFI, such as palette modes or EDID support. We should have DRM drivers for VESA and EFI interfaces. The infrastructure exists already and initial drivers can be forked from simpledrm.
Goals
- Initially, a bare driver for VESA or EFI should be created. It can take functionality from simpledrm.
- Then we can begin to add additional features. The boot loader can provide EDID data. With VGA hardware, VESA can support paletted modes or color management. Example code exists in vesafb.