SPARC frame buffer drivers typically do not operate in VGA text mode. SPARC frame buffer drivers typically are required to send pixel patterns that depict the text and images displayed. The kernel tem requires SPARC drivers to support specific interfaces to facilitate rendering data to the screen, perform scrolling, and display a text cursor. How the driver actually renders data sent from the tem onto the screen depends on the device. The driver typically draws the data into video memory according to the hardware and video mode.
The Solaris OS provides interfaces that enable the kernel terminal emulator to drive compatible console frame buffers directly. The advantages of converting a driver to be compatible with the kernel terminal emulator are:
Dramatically improved performance, particularly for scrolling
Enhanced ANSI text color capabilities
The ability to start a login session on the console frame buffer even when the system console stream is directed out the serial port
SPARC console frame buffer drivers are not required to be compatible with the kernel terminal emulator. If the console frame buffer driver is not compatible with the kernel terminal emulator, the system uses the FCode terminal emulator in the OpenBoot PROM.
The console frame buffer is identified through the EEPROM screen environment variable. The system determines whether the console frame buffer is compatible with the kernel terminal emulator module by checking whether the frame buffer driver exports the tem-support DDI property. If the tem-support property is exported, then the system issues the VIS_DEVINIT I/O control (ioctl) command to the frame buffer driver during system boot, while configuring the console. If the tem-support DDI property is exported and the VIS_DEVINIT ioctl command succeeds and returns a compatible version number to the tem, the system configures the system console to utilize that frame buffer driver through the kernel terminal emulator. See the ioctl(9E) man page for information about the I/O control driver entry point.
SPARC drivers that support the kernel terminal emulator should export the tem-support DDI property. This property indicates that the driver supports the kernel terminal emulator. If a frame buffer driver exports the tem-support DDI property, then that driver will be handled early in the boot process, while the console is being configured. If a frame buffer driver does not export the tem-support property, then that driver might not be handled early enough in the boot process.
When set to 1, this DDI property indicates that this driver is compatible with the console kernel frame buffer interface.
The kernel terminal emulator module interacts with the console frame buffer driver through two major interfaces:
Through ioctl interfaces during normal system operation
Through polled I/O interfaces during standalone mode
The following section provides detailed information.