framebuf.7 (2010 09)

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framebuf(7) framebuf(7)

NAME

framebuf - information for raster frame-buffer devices

SYNOPSIS

#include <sys/framebuf.h>

DESCRIPTION

Frame-buffer devices are raster-based displays. These devices use memory-mapped I/O to obtain much

higher performance than possible with tty-based graphic terminals. Frame-buffer devices can be accessed

directly using this interface, although access through the graphics libraries is recommended. Direct

access to frame-buffer devices entails precise knowledge of the frame-buffer architecture being used.

Input cannot be piped into or redirected to frame-buffer devices because they are not serial devices.

Each frame-buffer device is associated with a character special ﬁle. Major and minor numbers for frame-

buffer devices are implementation-dependent. The minor numbers for these devices denote different

frame buffers. Implementation-speciﬁc details are discussed in the appropriate systems administrator’s

manuals.

Communication with a frame-buffer device begins with an

open() system call. Multiple processes can

have the frame-buffer device open concurrently.

close() invalidates the ﬁle descriptor associated with the frame-buffer device. After a close() sys-

tem call, any access to the frame-buffer device address range might result in a memory fault and the sig-

nal SIGSEGV being sent to the process (see signal (2)). A process cannot unmap the frame buffer from its

address space after the frame-buffer special ﬁle is closed. To unmap a frame buffer, use the

GCUNMAP

ioctl() call (see below).

Once a process acquires a lock for the frame-buffer device, it must unlock it explicitly before calling

close(); see GCUNLOCK below.

read() and write() system calls are undeﬁned and always return an error. In this case

errno is set

to [ENODEV].

The

ioctl() system call is used to control a frame-buffer device. The select() system call is used to

test the frame-buffer device for exceptional conditions. Interrupts from the graphic hardware are con-

sidered exceptional conditions. An exceptional condition is automatically cleared after any process that

opens the frame-buffer device is notiﬁed of the exception by a select() call. A call to

select() for

read or write on the ﬁle descriptor associated with the frame-buffer device returns a false condition in the

read and write bit masks (see select (2)).

A frame-buffer device can be accessed by multiple processes at once. However, each process overwrites

the output of the others unless one of the lock mechanisms described here or some other synchronization

mechanism is used. The lock mechanisms described here are intended for cooperating processes only.

For all frame buffers, data bytes scan from left to right and from top to bottom. A pixel, which is a visible

dot on the screen, is associated with a location in the frame buffer. Each device maps one or more bits in

memory to a pixel on the screen, although the bits in the frame buffer might not be continuous. Informa-

tion describing the frame-buffer structure and attributes is found in the

crt_frame_buffer_t data

structure. The

crt_frame_buffer_t data structure includes the following ﬁelds:

int crt_id; /*display identifier*/

unsigned int crt_attributes; /*flags denoting attributes*/

char *crt_frame_base; /*first byte in frame-buffer memory*/

char *crt_control_base; /*first byte of the control*/

/*registers*/

char *crt_region [ CRT_MAX_REGIONS ];

/*other regions associated with the*/

/*frame-buffer device*/

The following are valid

ioctl() requests:

GCDESCRIBE Describe the size, characteristics, and mapped regions of the frame buffer. The

information is returned to the calling process in a crt_frame_buffer_t data

structure, and the parameter is deﬁned as crt_frame_buffer_t *arg;.

Although some structure ﬁelds contain addresses of one or more frame-buffer device

regions, the values of these ﬁelds are not always deﬁned. Only after a successful

GCMAP command is issued (see below) are the correct addresses returned so the

user can access the frame-buffer regions directly using the returned addresses.

HP-UX 11i Version 3: September 2010 − 1 − Hewlett-Packard Company 1

Summary of content (6 pages)

PAGE 1
framebuf(7) framebuf(7) NAME framebuf - information for raster frame-buffer devices SYNOPSIS #include DESCRIPTION Frame-buffer devices are raster-based displays. These devices use memory-mapped I/O to obtain much higher performance than possible with tty-based graphic terminals. Frame-buffer devices can be accessed directly using this interface, although access through the graphics libraries is recommended.
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framebuf(7) A framebuf(7) GCID Provide a device identification number. The parameter is defined as int *arg;. The information returned when using this command is a subset of the information provided by GCDESCRIBE, and is provided here for backward compatibility only. GCON, GCOFF Turn graphics on or off. These operations are valid for devices whose CRT_GRAPHICS_ON_OFF bit is set in the crt_attributes field of the crt_frame_buffer_t data structure returned by the GCDESCRIBE command.
PAGE 3
framebuf(7) framebuf(7) blocked signals. The signals are not blocked until the lock is actually acquired, and might be received while still awaiting the lock. The signal SIGTSTP is also blocked whether or not it is being caught. The signals SIGTTIN and SIGTTOU are also blocked on frame-buffer devices where the ITE does not output to the device while it is locked. See DEPENDENCIES below.
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framebuf(7) framebuf(7) image needs to be refreshed. The window image is then a superset of the rectangle being updated, and might thus have different dimensions. The skipcount specifies the portion of the row in the larger window image that is excluded from the rectangle. Thus, linelength plus skipcount would be the number of bytes in each row of the larger window image array.
PAGE 5
framebuf(7) framebuf(7) AUTHOR framebuf was developed by HP. SEE ALSO mknod(1M), close(2), ioctl(2), lockf(2), open(2), select(2), signal(2), sigsetmask(2), termio(7).
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(Notes) A (Notes) fA 6 Hewlett-Packard Company −1− HP-UX 11i Version 3: September 2010