This is a discussion on Linux-Video Subsystem within the Operating systems forums, part of the Tutorials category; Linux-Video Subsystem:- The concept of frame buffers is central to video on Linux, so let's first find out what that ...
The concept of frame buffers is central to video on Linux, so let's first find out what that offers. Because video adapters can be based on different hardware architectures, the implementation of higher kernel layers and applications might need to vary across video cards. This results in nonuniform schemes to handle different video cards. The ensuing nonportability and extra code necessitate greater investment and maintenance. The frame buffer concept solves this problem by describing a general abstraction and specifying a programming interface that allows applications and higher kernel layers to be written in a platform-independent manner. Figure (given below) shows you the frame buffer advantage.
(The frame buffer advantage.)
The kernel's frame buffer interface thus allows applications to be independent of the vagaries of the underlying graphics hardware. Applications run unchanged over diverse types of video hardware if they and the display drivers conform to the frame buffer interface. As you will soon find out, the common frame buffer programming interface also brings hardware independence to kernel layers, such as the frame buffer console driver. Today, several applications, such as web browsers and movie players, work directly over the frame buffer interface. Such applications can do graphics without help from a windowing system.
The X Windows server (Xfbdev) is capable of working over the frame buffer interface, as shown in the Figure (given below).
The Linux-Video subsystem shown in the above Figure is a collection of low-level display drivers, middle-level frame buffer and console layers, a high-level virtual terminal driver, user mode drivers part of X Windows, and utilities to configure display parameters. Let's trace the figure top down:
1. The X Windows GUI has two options for operating over video cards. It can use either a suitable built-in user-space driver for the card or work over the frame buffer subsystem.
2. Text mode consoles function over the virtual terminal character driver. Like X Windows, text consoles have two operational choices. They can either work over a card-specific console driver, or use the generic frame buffer console driver (fbcon) if the kernel supports a low-level frame buffer driver for the card in question.