OLED brightness in Linux

Recently I've got a new laptop with OLED panel only to find out that brightness control for OLED panels is not yet supported in Linux. Archlinux wiki page mentions using gamma ramp for controlling perceived brightness using hackish userspace tools (icc-brightness), so my first thought was to implement a hack for i915 driver to expose backlight interface that actually adjusts gamma ramp. So I went to #dri-devel to ask around whether this idea sounds too crazy and it turned out that there are better ways than using gamma ramp. Basically if you use gamma ramp you essentially reduce dynamic range, i.e. if you have 8 bits per pixel at 50% brightness you would get 7 bit, at 25% - 6 bit and that will result in banding artefacts at low brightness levels. To overcome that issue OLED panels actually have an interface to control brightness. There are at least 2 competing "standards" - VESA and Intel proprietary. First one is already supported by i915 driver while latter is not. Unfo

Hacking u-boot for Pinebook. Part #1 - using FEL

It's been a while since I posted to my blog. A lot of things happened since then, I guess the most important is -- I moved to Canada. I've been living in Vancouver (OK, Greater Vancouver) with my wife and cat for more than 2 years now. But enough about me, let's get back to the topic. Recently I've got a Pinebook , mostly for hacking purposes. It's pretty nice device - quad-core Allwinner A64 CPU, 2GB LPDDR3 RAM, eMMC storage, etc, etc. See for full specs. But unfortunately it comes with BSP kernel from Allwinner which is pretty ancient - 3.10 (released in 2013, more than 4 years ago!) Hopefully, mainline support for A64 is in pretty decent shape, see . Sure some things are missing - LCD, sound, power management, and that's not all. But it's good - there's something to hack on, right? So I decided to start with u-boot. Hopefully, Allwinner SoCs support boot over USB - it's called FEL,

Access point with Raspberry Pi and rtl8192cu dongle

On Thursday ethernet ports (WAN and LAN1-4) in my Asus WL500GPv1 router have completely died, so I needed a replacement. Hopefully, recently I've got Raspberry Pi, so I decided to use it as a router. I've got TP-LINK TL-WN821NC USB stick from local store which is based on RTL8192CU chipset. Unfortunately, its driver doesn't work with vanilla hostapd, but requires patched ancient version of hostapd from Realtek . I'm using Archlinux on my rpi and I've found manual how to setup AP using this USB stick  here , but I don't want to overwrite binaries from repository packages, since it's not a sane way, and it can (and will) be broken by hostapd update. So I prepared a package, here's source package (just unpack it and build with makepkg directly on rpi), and here's binary package for armv6h (you can install it with pacman -U). I can't put PKGBUILD in AUR, since there's no stable hosting for Realtek's hostapd. If anyone is willing to host

topIcons extension for gnome-3.8

Well, I dislike gnome devs decision about putting legacy tray icons to the attic (message tray), and prior to gnome 3.8 there was an extension to move all tray icons to the top panel. But after upgrade to gnome-3.8 subj extension didn't work properly (tray icons disappear after locking/unlocking screen). I've waited for a fix about a week, and then I decided to fix it by myself, result is on github .

Wayland and software rendering

Recently I spent few evenings for hacking wayland . I like idea of wayland - rendering is done completely on client (in whatever way), compositor (server part) is responsible in rendering buffers from clients on the screen. Issue for me was rendering part of weston (reference compositor for wayland) - it uses GLES for compositing, but I want to try wayland and weston on devices without hw acceleration (pure software rendering), and running software GL on PXA270@312MHz does not sound like a good idea, does it? :) So I asked on if it possible to implement software renderer, Kristian Høgsberg (khr) responded that in master branch of weston repo there's a nice abstraction of renderer, so it's possible to implement pixman renderer. So I did :) weston with x11-backend and pixman renderer khr and pq from #wayland were very helpful, and described place of renderer in wayland architecture, here're some points renderer just performs rendering of

gnome 3.6 and keyboard layout configuration

Gnome 3 devs are stupid enough to remove features before some replacement is implemented. Simplified nautilus and (what's much more important for me!) broken keyboard layout configuration. Well, you still can configure what layouts to use, but you can't choose usual shortcut to switch layout, and you can't configure led to indicate alternative layout. Well, I still can use setxkbmap (setxkbmap -layout "us,ru" -option "grp:caps_toggle,grp_led:scroll"), but that's f***ing ridiculous to remove things that were working here for years and propose nothing for replacement! They broke core functionality (who can work without a keyboard?!), and it makes me sick! Update:  more haterays to gnome-devs! Gnome 3 overrides xkbmap settings somewhere, I wonder if there's a way to prevent it... Update-2:  you can remove gnome-settings-daemon keyboard plugin as a workaround (sudo rm /usr/lib/gnome-settings-daemon-3.0/

ArchLinux and broken gnome-settings-daemon

Just another post of hate. This time rays of hate go to maintainers of archlinux Gnome 3  packages. In short words: global hotkeys are broken in Gnome-3.4 when using it with recent xorg-server upstream patch exists, however no tarball was released (who cares!) ArchLinux Gnome 3 package maintainers are lazy enough to import this patch and rebuild package bug was reported and closed as "won't fix" because they're waiting for gnome-3.6.1 to stabilize and enter into extra repo. Users suffer from bug for ~3 weeks! They even do not need to investigate what causes problem, patch exists. Btw, I've even created a source package and sent them a link. Some user from archlinux bbs  created package in aur I'm still wondering why they do not respect their users...