Section "Device" Identifier "devname" Driver "fbturbo" ... EndSection
fbturbo is an Xorg driver for Allwinner and other ARM-based devices, derived from fbdev driver. With regard to 2D graphics, it provides a number of software optimizations on all platforms, while letting the SIMD (ARM NEON) accelerated code from the pixman library run at full speed without any unnecessary overhead. 2D hardware acceleration using G2D is supported on sunxi platforms. The recommended framebuffer color depths are 16 (RGB565) and 24 (XRGB8888), the other color depths may be supported too. Multi-head configurations are supported.
The fbturbo driver supports all hardware where a framebuffer driver is available and uses the os-specific submodule fbdevhw(4) to talk to the kernel device driver. Currently a fbdevhw module is available for linux. Additionally it is intended to use some of the display controller features from Allwinner A10/A13 SoC and provide the necessary DRI2 integration with the proprietary OpenGL ES binary blobs for Mali400 GPU (if they are installed in the system). The part related to Mali400 GPU support is derived from the vendor provided open source xf86-video-mali driver.
Please refer to xorg.conf(5) for general configuration details. This section only covers configuration details specific to this driver.
For this driver it is not required to specify modes in the screen section of the config file. The fbturbo driver can pick up the currently used video mode from the framebuffer driver and will use it if there are no video modes configured.
The following driver Options are supported:
- Option "fbdev" "string"
The framebuffer device to use. Default: /dev/fb0.
- Option "ShadowFB" "boolean"
Enable or disable use of the shadow framebuffer layer. Default: off on most platforms (any hardware that supports NEON, VFP, or 2D hardware acceleration).
- Option "Rotate" "string"
Enable rotation of the display. The supported values are "CW" (clockwise, 90 degrees), "UD" (upside down, 180 degrees) and "CCW" (counter clockwise, 270 degrees). Implies use of the shadow framebuffer layer. Default: off.
- Option "UseBackingStore" "boolean"
Enable the use of backing store for certain windows at the bottom of the stacking order. This allows to avoid expensive redraws caused by expose events when dragging one window on top of another. The default heuristics tries to be "smart" and avoid backing store allocation for the active window which has keyboard focus. The purpose is to get the best balance between performance and memory footprint without introducing full compositing overhead. Default: inverse of ShadowFB
- Option "ForceBackingStore" "boolean"
Same as "UseBackingStore" option, but don't apply any heuristics and just allocate backing store for all windows.
- Option "HWCursor" "boolean"
Enable or disable the HW cursor. Supported on sunxi platforms. Default: on if supported, off otherwise.
- Option "DRI2" "boolean"
Enable or disable DRI2 integration for Mali GPU. Provides hardware accelerated OpenGL ES in the case if proprietary blob libMali.so is installed in the system and linux kernel provides modules mali.ko, mali_drm.ko and ump.ko with compatible version (for example, both kernel modules and libMali.so can have revision r3p0). Default: on.
- Option "DRI2HWOverlay" "boolean"
Enable the use of display controller hardware overlays (aka "layers", "windows", ...) for fully visible DRI2 backed OpenGL ES windows in order to avoid expensive memory copy operations. That's a zero-copy solution which eliminates unnecessary CPU overhead. Default: on.
Note: the hardware overlays are automatically disabled in the case if a compositing window manager (xfwm4, kwin, ...) is used for various fancy desktop effects such as windows translucency or shadows. Maybe some improvements are possible in this area. But if you really care about the desktop performance, then you likely don't want to enable any compositing effects in your window manager anyway.
- Option "SwapbuffersWait" "boolean"
This option controls the behavior of eglSwapBuffers calls by OpenGL ES applications. If enabled, the calls will try to avoid tearing by making sure the display scanline is outside of the area to be copied before the copy occurs. If disabled, no scanline synchronization is performed, meaning tearing will likely occur. Note that when enabled, this option can adversely affect the framerate of applications that render frames at less than refresh rate. Default: enabled.
- Option "AccelMethod" "string"
Chooses between available acceleration architectures. Valid values are G2D and CPU. G2D is only available on sunxi hardware with G2D support (such as A10). The default is G2D on supported platforms, CPU on others.
- Option "XVHWOverlay" "boolean"
Enable or disable the use of display controller hardware overlays for XVideo acceleration. Only available on sunxi hardware. Default: on if supported, off otherwise.
Xorg(1), xorg.conf(5), Xserver(1), X(7), fbdevhw(4)
Authors include: Gerd Knorr, Michel Dänzer, Geert Uytterhoeven, Siarhei Siamashka