root@hobbes.UUCP (John Plocher) (07/03/87)
+---- Scott Crenshaw writes the following in article <1502@rti.UUCP> ---- | | Has anyone successfully written to video memory using | MicroPort's shm scheme ? | | Scott Crenshaw +---- Sorry for posting; rti doesn't seem to be in my uucp maps... :-( (See also the Microp Newsletter: seismo!umix!b-tech!microp microp%b-tech.uucp%umix.cc.umich.edu ) First some background: -------------- Date: Mon, 11 May 87 11:55:42 PDT To: admin!uport!amdcad!ames!uwvax!uwmacc!hobbes!plocher Subject: shmcreate There is a known problem with shmcreate - the address space is not correctly correlated with the physical address space of the video memory. This is being worked on and should be fixed soon. Keith ------------- Date: Tue, 12 May 87 22:19:01 PDT To: uwvax!sdamos.UCSD.EDU!uwvax!uwmacc!hobbes!root Subject: Re: Microport shmcreate There is a workaround for shmcreate. Use the old shmvidkey utility. I found that works just fine (although it may leave the protection bits on the segment in a bad state). Cheers, Dave ------------- Date: Thu, 11 Jun 87 23:21:25 PDT To: admin!uport!amdcad!ames!uwvax!uwmacc!hobbes!root Subject: Shmcreate fix Your current version of shmcreate can be patched so that it will work. Type: /etc/patch /etc/shmcreate -b +-831 noerror 74 It should now work. The problem was that it did not attach the returned shared memory segment to the physical address of the video card. Good luck!!! Keith Hankin Microport Systems ---------- Then the example program: ------------------------------------------------------------------------------ ( Microp Newsletter Volume 26 ) From: <itivax.uucp!umix!rutgers!uwvax!uwmacc!hobbes!plocher> Subject: Example program for accessing screen + fix for shmcreate Here is a simple demo of what can be done whth shared memory when accessing the IBM's screen. This assumes you have a working version of shmcreate. (See above patch) This program starts a daemon which runs in the background and displays the time on the 25th line of the screen. NOTE: define either MONO or COLOR when compiling so that the program will put the time display on the correct monitor. Note also that this program ASSUMES that the color display is NOT in graphics mode (Iff COLOR is defined :-). Compile with: cc -Ml -O -o clockline clockline.c To turn off the clock, find it's PID with ps, then send it a SIGTERM (15) signal with kill. % ps -eaf UID PID PPID C STIME TTY TIME COMMAND root 0 0 50 Jun 6 ? 4297:50 swapper root 1 0 0 Jun 6 ? 25:41 [ init ] root 117 1 0 Jun 6 console 0:37 -csh root 305 1 0 Jun 6 ? 13:55 clockline root 19825 19824 35 14:33:51 console 0:01 ps -eaf % kill -15 305 John _______________________ /* clock.c - clock on 25th line */ /* * This program assumes the existance of shared memory segments * set up by shmcreate to allow access to video memory on the * display adapters: * * /etc/shmcreate 0xb8000 b8000 32768 # cga * /etc/shmcreate 0xb0000 b0000 4096 # mda */ # include <sys/types.h> /* system types */ # include <stdio.h> # include <sys/ipc.h> # include <sys/shm.h> # include <errno.h> # include <signal.h> /* DEFINE only ONE of these */ #define MONO /* display time on the MONOCHROME monitor */ /* #define COLOR /* display time on the COLOR (CGA) monitor */ #ifdef MONO #define VIDKEY 0xb0000 #else /* COLOR */ #define VIDKEY 0xb8000 #define VIDLEN 4096 #define VIDFLAGS 0 unsigned short *get_statusline_shm(); char *shmat(); extern char *ctime(); unsigned short *statusline; long now; static char *signames[] = { "signals", "SIGHUP (Hangup)", "SIGINT (User interrupt)", "SIGQUIT (User abort)", "SIGILL (Illegal instruction)", "SIGTRAP (Trace trap)", "SIGIOT (IOT instruction)", "SIGEMT (EMT instruction)", "SIGFPE (Floating point exception)", "SIGKILL (If you see this, Unix is broke)", "SIGBUS (Bus error)", "SIGSEGV (Segmentation violation)", "SIGSYS (Bad argument to a system call)", "SIGPIPE (Broken pipe)", "SIGALRM (Alarm clock)", "SIGTERM (Software termination signal)", "SIGUSR1", "SIGUSR2", "SIGCLD (Death of a child)", "SIGPWR (Power is failing)" }; void done( value ) int value; { int i; /* Clear status line */ for (i = 0; i < 80; i++) statusline [i + 24*80] = 0x0720; /* Detach from shared memory segment */ if (shmdt((char *) statusline) == -1) perror("shmdt"); /* Do the generic stuff I like to do when dying... */ time( &now ); if (value > 0) fprintf(stderr,"Caught signal %d: %s\n", value, signames[ value ]); else if (value == 0) fprintf(stderr,"Abnormal completion\n"); else fprintf(stderr,"INTERNAL ERROR %d\n", -value); fprintf(stderr,"statline terminated on %s", ctime(&now)); exit(value); /* Killing oneself with a SIGKILL will also work... */ } main () { int i; char buf[80]; /* detach from the invoking terminal's process group */ switch (fork()) { /* put self in background */ case -1: perror("fork"); exit(1); case 0: break; default: exit(0); } setpgrp(); /* detach from the tty which started us */ /* so <del> and <^\> don't kill us */ for (i= SIGHUP; i <= SIGPWR; i++ ) /* die on any signal recieved */ signal(i, done); statusline = get_statusline_shm(); for(;;) { time( &now ); /* get time */ sprintf(buf,"%s", ctime( &now )); for (i = 0; i < strlen(buf) -1; i++) /* display time */ statusline [i + 25 + 24*80] = 0x0700 | buf[i]; /* i is the offset from the start of the time display */ /* 25 is the starting offset from the beginning of line 25 */ /* so the 'clock' is centered */ /* 24*80 is the beginning of the 25th line of the screen */ /* 0x0700 sets the attribute byte */ sleep(1); } } unsigned short *get_statusline_shm() { char *vidram, *shmat(); int shmid; extern int errno; if ((shmid = shmget ((key_t)VIDKEY, VIDLEN, VIDFLAGS)) == -1) { done( -7 ); } if ((vidram = shmat (shmid, (char *) 0, 0)) == (char *) -1) done( -8 ); return (unsigned short *)vidram; } -- * * * * Note email address change as of 7/1/87 * * * * John Plocher UUCP: <backbone>!uwvax!geowhiz!uwspan!plocher ============== Internet: plocher%uwspan.UUCP@uwvax.cs.Wisc.EDU FidoNet: 121/0 BITNET: uwvax!geowhiz!uwspan!plocher@psuvax1