genode/doc/components.txt

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==========================
Genode components overview
==========================
Norman Feske
Abstract
########
Genode comes with a growing number of components apparently scattered across
various repositories. This document provides an overview of these components
and outlines the systematics behind them.
Categorization of components
############################
Genode components usually fall into one of four categories, namely device
drivers, resource multiplexers, protocol stacks, and applications. Each
of them is briefly characterized as follows:
:Device drivers: translate hardware resources into device-independent
session interfaces. Naturally, a device driver is specific to a
particular hardware platform. The hardware resources are accessed
via core's IO_MEM, IO_PORT, and IRQ services. The functionality of
the driver is made available to other system components by announcing
one of Genode's device-independent session interfaces, which are
'pci_session', 'framebuffer_session', 'input_session', 'block_session',
'audio_out_session', 'log_session', 'nic_session', and 'timer_session'
(see 'os/include/' for the interface definitions). Those interfaces are
uniform across hardware platforms and kernel base platforms. Usually,
each device driver can accommodate only one client at a time.
:Resource multiplexers: provide mechanisms to multiplex device resources
to multiple clients. A typical resource multiplexer requests one
of Genode's device-independent session interface (usually connected
to a device driver) and, in turn, announces a service of the same kind.
However, in contrast to a device driver, a resource multiplexer is able
to serve more than one client at the same time.
:Protocol stacks: translate low-level interfaces to higher-level
interfaces (or sometimes vice versa). Typically, a protocol stack comes
in the form of a library, which uses a device-independent session
interface as back end and provides a high-level library interface as
front end. However, protocol stacks also exist in the form of
distinct components that implement translations between different
session interfaces.
:Applications: implement functionality using APIs as provided by
protocol stacks.
:Runtime environments: enable existing 3rd-party software to be executed
as a Genode sub systems.
Device drivers
##############
Device drivers usually reside in the 'src/drivers' subdirectory of source-code
repositories. The most predominant repositories hosting device drivers are
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'os', 'linux_drivers', 'dde_ipxe', 'dde_linux'.
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Platform devices
================
:'os/src/drivers/pci':
Implements the PCI-session interface using the PCI controller as found on
x86 PC hardware. Using this interface, a client can probe for a particular
device and request information about physical device resources (using the
'pci_device' interface). These information are subsequently used to request
respective IO_MEM, IRQ, and IO_PORT sessions at core.
UART devices
============
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The UART device drivers implement the UART-session interface.
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:'os/src/drivers/uart/pl011':
Driver for the PL011 UART as found on many ARM-based platforms.
:'os/src/drivers/uart/i8250':
Driver for the i8250 UART as found on PC hardware.
Framebuffer and input drivers
=============================
Framebuffer and input drivers implement the framebuffer-session interface and
input-session interfaces respectively.
:'os/src/drivers/input/dummy':
Pseudo input driver without accessing any hardware. This component is useful
to resolve a dependency from an input session for scenarios where no user
input is required.
:'os/src/drivers/input/fiasco_ux':
Driver for the virtual hardware provided by the user-mode version of the
Fiasco kernel.
:'os/src/drivers/input/ps2/x86':
Driver for the 'i8042' PS/2 controller as found in x86 PCs. It supports both
mouse (including ImPS/2, ExPS/2) and keyboard.
:'os/src/drivers/input/ps2/pl050':
Driver for the PL050 PS/2 controller as found on ARM platforms such as
VersatilePB. The physical base address used by the driver is obtained at
compile time from a header file called 'pl050_defs.h'. The version of the
VersatilePB platform can be found at 'os/include/platform/vpb926/' and
is made available to the driver via the SPECS machinery of the Genode build
system.
:'os/src/drivers/framebuffer/vesa':
Driver using VESA mode setting on x86 PCs. For more information, please refer
to the README file in the driver directory.
:'os/src/drivers/framebuffer/pl11x':
Driver for the PL110/PL111 LCD display.
:'os/src/drivers/framebuffer/sdl':
Serves as both framebuffer and input driver on Linux using libSDL. This
driver is only usable on the Linux base platform.
:'os/src/drivers/framebuffer/fiasco_ux':
Driver for the virtual framebuffer device provided by the user-mode Fiasco
kernel.
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:'dde_linux/src/drivers/usb':
USB driver that makes USB HID and USB storage devices available as input
sessions and block session respectively. For examples of using this driver,
refer to the run scripts at 'dde_linux/run/usb_hid' and
'dde_linux/run/usb_storage'.
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Timer drivers
=============
All timer drivers implement the timer-session interface. Technically, a timer
driver is both a device driver (accessing a timer device) and a resource
multiplexer (supporting multiple timer-session clients at the same time). The
timer implementations differ in their use of different time sources and the
mode of internal operation of the timer sessions. Time sources are either
hardware timers, a time source provided by the kernel, or a pseudo time source
(busy).
The internal operation of the timer session depends on the kernel. On kernels
with support for out-of-order RPCs, all timer sessions are handled by a single
thread. Otherwise, each timer session uses a dedicated thread.
:'timer/nova': PIT as time source, multi-threaded
:'timer/codezero': busy time source, single-threaded
:'timer/okl4_arm': busy time source, single-threaded
:'timer/okl4_x86': PIT as time source, single-threaded
:'timer/foc': IPC timeout as time source, multi-threaded
:'timer/fiasco': IPC timeout as time source, single-threaded
:'timer/pistachio': IPC timeout as time source, single-threaded
:'timer/linux': nanosleep as time source, single-threaded
Audio output drivers
====================
All audio-output drivers implement the audio session interface defined at
'os/include/audio_out_session/'.
:'os/src/drivers/audio_out/linux':
Uses ALSA as back-end on the Linux base platform.
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:'dde_oss/src/drivers/oss':
Sound drivers for the most common PC sound hardware, ported from the
Open Sound System project.
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:'linux_drivers/src/drivers/audio_out':
Sound drivers for the most common PC sound hardware, ported from the Linux
kernel.
Block drivers
=============
All block drivers implement the block-session interface defined at
'os/include/block_session/'.
:'os/src/drivers/atapi':
Driver for ATAPI CD-ROM devices on x86 PCs.
:'os/src/drivers/sd_card':
Driver for SD-cards connected via the PL180 device as found on the PBX-A9
platform.
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:'os/src/drivers/sd_card/omap4':
Driver for SD-cards connected to the SD-card controller of the OMAP4 SoC.
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:'linux_drivers/src/drivers/usb':
USB driver that makes USB storage devices available as block sessions.
For an example of using this driver, refer to the run script at
'linux_drivers/run/usb_storage'.
:'os/src/drivers/ahci':
Driver for SATA disks on x86 PCs.
Network interface drivers
=========================
All network interface drivers implement the NIC session interface
defined at 'os/include/nic_session'.
:'os/src/drivers/nic/linux':
Driver that uses a Linux tap device as back end. It is only useful on the
Linux base platform.
:'os/src/drivers/nic/lan9118':
Native device driver for the LAN9118 network adaptor as featured on the
PBX-A9 platform.
:'dde_ipxe/src/drivers/nic':
Device drivers ported from the iPXE project. Supported devices are Intel
E1000 and pcnet32.
:'linux_drivers/src/drivers/madwifi':
The MadWifi wireless stack ported from the Linux kernel.
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:'dde_linux/src/drivers/usb':
For the OMAP4 platform, the USB driver contains the networking driver.
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General-purpose I/O drivers
===========================
:'os/src/drivers/gpio/omap4':
Driver for accessing the GPIO pins of OMAP4 platforms.
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Resource multiplexers
#####################
By convention, resource multiplexers are located at the 'src/server'
subdirectory of a source repository.
:Framebuffer and input: The framebuffer and input session interfaces can be
multiplexed using the Nitpicker GUI server, which allows multiple clients to
create and manage rectangular areas on screen. Nitpicker uses one input
session and one framebuffer session as back end and, in turn, provides
so-called nitpicker sessions to one or multiple clients. Each nitpicker
session contains a virtual framebuffer and a virtual input session. Nitpicker
(including a README file) is located at 'os/src/server/nitpicker'.
:Audio output: The audio mixer located at 'os/src/server/mixer' enables
multiple clients to use the audio-out interface. The mixing is done by simply
adding and clamping the signals of all present clients.
:Networking: The NIC bridge located at 'os/src/server/nic_bridge' multiplexes
one NIC session to multiple virtual NIC sessions using a proxy-ARP
implementation. Each client has to obtain a dedicated IP address visible to
the physical network. DHCP requests originating from the virtual NIC sessions
are delegated to the physical network.
:Block: The block-device partition server at 'os/src/server/part_blk' reads
the partition table of a block session and exports each partition found as
separate block session. For using this server, please refer to the run
script at 'os/run/part_blk'.
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:File system: The FFAT file-system service allows multiple clients to
concurrently access the same FFAT-formatted block device. It is located
at 'libports/src/server/ffat_fs'.
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Protocol stacks
###############
Protocol stacks come either in the form of separate components that translate
one session interface to another, or in the form of libraries.
Separate components:
:'os/src/server/nit_fb':
Translates a nitpicker session to a pair of framebuffer and input sessions.
Each 'nit_fb' instance is visible as a rectangular area on screen presenting
a virtual frame buffer. The area is statically positioned. For more
information, please refer to 'os/src/server/nit_fb/README'.
:'demo/src/server/liquid_framebuffer':
Implements the same translation as 'nit_fb' but by presenting an interactive
window rather than a statically positioned screen area.
:'os/src/server/tar_rom':
Provides each file contained in a tar file obtained via Genode's ROM session
as separate ROM session.
:'os/src/server/iso9660':
Provides each file of an ISO9660 file system accessed via a block session as
separate ROM session.
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:'os/src/server/ram_fs':
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A file-system implementation that keeps all data in memory.
:'os/src/server/tar_fs':
A read-only file-system implementation that reads data from a TAR archive,
which, in turn, is provided by a ROM service.
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:'os/src/server/rom_loopdev':
Provides the content of a ROM file as a block session, similar to the
loop-mount mechanism on Linux
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:'os/src/server/terminal_log':
Adapter for forwarding LOG messages to a terminal session.
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:'demo/src/server/nitlog':
Provides a LOG session, printing log output on screen via a nitpicker
session.
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:'gems/src/server/terminal':
Provides a terminal session via a graphical terminal using a framebuffer
session and an input session.
:'gems/src/server/tcp_terminal':
Provides one or multiple terminal sessions over TCP connections.
For further information, refer to 'gems/src/server/tcp_terminal/README'.
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:'os/src/server/terminal_crosslink':
The terminal crosslink service allows to terminal clients to talk to each
other.
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:'gems/src/server/http_block':
A block service that fetches a virtual block device over the network from
a HTTP server.
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Libraries:
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:'libports/lib/mk/libc':
C runtime ported from FreeBSD.
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:'libports/lib/mk/libc_log':
Redirects the standard output of the libc to Genode's LOG session interface.
:'libports/lib/mk/libc_lwip_nic_dhcp':
Translates the BSD socket API to a NIC session using the lwIP stack.
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:'libports/lib/mk/libc_fs':
Allows libc-using programs to access the Genode file-system infrastructure
using the POSIX file API.
:'libports/lib/mk/libc_terminal':
Connects the standard input and output from/to Genode's terminal session
interface.
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:'libports/lib/mk/stdcxx':
Standard C++ library
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:'libports/lib/mk/gallium' + 'linux_drivers/lib/mk/gpu_i915_drv':
Translates the OpenGL API to a framebuffer session using the MESA OpenGL
stack and the Intel GEM GPU driver.
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:'libports/lib/mk/pthread':
Subset of the POSIX thread and semaphore API.
:'libports/lib/mk/python':
Runtime of the Python scripting language.
:'libports/lib/mk/mupdf':
PDF rendering engine.
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:'libports/lib/mk/sdl':
Translates the libSDL API to framebuffer and input sessions.
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:'libports/lib/mk/ncurses':
Library for implementing pseudo-graphical applications (i.e., VIM) that
run on a text terminal.
:'libports/lib/mk/avcodec':
A library for video decoding, conversion, and streaming.
:'libports/lib/mk/lua':
Runtime for the Lua scripting language.
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:'qt4':
Qt4 framework, using nitpicker session and NIC session as back end.
Applications
############
Applications are Genode components that use other component's services but
usually do not provide services. They are typically located in the 'src/app/'
subdirectory of a repository. Most applications come with README files
located in their respective directory.
:'demo/src/app/backdrop':
Nitpicker client application that sets a PNG image as desktop background.
:'demo/src/app/launchpad':
Graphical application for interactively starting and killing subsystems.
:'demo/src/app/scout':
Graphical hypertext browser used for Genode's default demonstration scenario.
:'libports/src/app/eglgears':
Example program for using OpenGL via the Gallium3D graphics stack.
:'ports/src/app/arora':
Arora is a Qt4-based web browser using the Webkit engine.
:'ports/src/app/gdb_monitor':
Application that allows the debugging of a process via GDB over a remote
connection.
:'qt4/src/app/qt_launchpad':
Graphical application starter implemented using Qt4.
:'qt4/src/app/examples/':
Several example applications that come with Qt4.
:'os/src/app/xvfb':
Is a proxy application that enables the integration of a virtual X server
into a Nitpicker session on the Linux base platform.
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:'ports/src/noux-pkg':
Ports of popular commandline-based Unix software such as VIM, bash,
coreutils, binutils, gcc, findutils, and netcat. The programs are supposed
to be executed within the Noux runtime environment.
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:'ports/src/app/lighttpd':
Lighttpd is a fast and feature-rich web server. The port of lighttpd uses
a file-system session to access the website content and the web-server
configuration.
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Runtime environments
####################
:'ports/src/noux': Noux is an experimental implementation of a UNIX-like API
that enables the use of unmodified command-line based GNU software. For using
noux, refer to the run script 'ports/run/noux.run'.
:'ports-okl4/src/oklinux': OKLinux is a paravirtualized Linux kernel that
enables the use of Linux-based OSes as subsystems on the OKL4 kernel. For
using OKLinux, refer to the run script 'ports-okl4/run/lx_block.run'.
:'ports-foc/src/l4linux': L4Linux is a paravirtualized Linux kernel that
enables the use of Linux-based OSes as subsystems on the Fiasco.OC kernel.
For using L4Linux, refer to the run script 'ports-foc/run/l4linux.run'.
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:'ports-foc/src/l4android': L4Android is a variant of L4Linux that is able
to execute the Android software stack on top of the Fiasco.OC kernel.
:'ports/src/vancouver': Vancouver is a virtual-machine monitor developed for
the use with the NOVA platform. It virtualizes 32bit x86 PC hardware
including various peripherals. The current version is regarded as work in
progress. It is able to bootstrap one of the Fiasco or Pistachio kernels
but support for interrupts (i.e., the timer) is not yet implemented.
:'os/src/server/loader': A service that allows the creation and destruction
of Genode subsystems via a session interface. For further information,
refer to 'os/src/server/loader/README'.
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