Hi, Martin
Thanks a lot for that blindingly fast turnaround!
Problems remain; I've attached an enhanced version of my tester that
will show them up. On Linux 2.4 my tester's fullscreen read() returns
a count of 15, and I suspect it should in Linux 2.6 as well.
As to /dev/3270/tub, believe me, devfs was the furthest thing from my
mind. Here's what I was talking about. Consider the device /dev/tty.
It exists to provide a path for the application to the current
controlling tty. What would the application have to do (absent
stdout/stderr) to access its controlling terminal if there was no
/dev/tty device? It wouldn't be easy, right?
Similarly, /dev/3270/tub needs to exist to provide a path for the
application to the fullscreen, when the controlling tty is in fact a
line-mode 3270 (and ENODEV otherwise).
Notice that the permissions of /dev/tty are crw-rw-rw and those of
/dev/3270/tub are crw-rw-rw as well. For /dev/tty notice the logic in
drivers/char/tty_io.c:tty_open(), right at retry_open:, where a test is
made for major 5, minor 0 (the maj/min of /dev/tty) and the device at
current->signal->tty is used. That's what /dev/3270/tub wants as well,
only of course to use the corresponding full-screen major number 228
with the minor number of the current->signal->tty device. In 2.4 I
reserved minor number 0 strictly for /dev/3270/tub, analogous to
/dev/tty, and I ensured that 227,N and 228,N referred to the same
physical device. That is, there was no 227,0 device: the console would
probably come in at 227,1. My test program should work with no operands
when invoked from a logged-on 3270: in that case, it opens /dev/3270/tub.
This hardly begins to address the issue you very rightly brought up, how
to make /dev/3270/tty0987 and /dev/3270/tub0987 for a new device, and
I'll try plowing into that.
Dick Hitt
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#include <errno.h>
#include <fcntl.h>
/* extracted from /usr/src/linux/drivers/s390/char/tubio.h --- */
#define TUB(x) (('3'<<8)|(x))
#define TUBICMD TUB(3)
#define TUBOCMD TUB(4)
#define TC_EWRITE 0x05
#define TC_READMOD 0x06
/* "Hello. world" in EBCDIC */
char Hello[] = { 0x40, /* Write Control Character (WCC) */
0x11, 0x40, 0x40, /* Set Buffer Address (SBA) */
0xc8, 0x85, 0x93, 0x93, 0x96, 0x6b, /* H e l l o , */
0x40, 0xe6, 0x96, 0x99, 0x93, 0x84 }; /* w o r l d */
main(int argc, char *argv[])
{
int fd, rc, i;
unsigned char buf[4096];
char *tub = "/dev/3270/tub";
if (argc >= 2)
tub = argv[1];
if ((fd = open(tub, O_RDWR)) == -1) {
printf("open(%s) failed with errno %d (%s)\n",
tub, errno, strerror(errno));
exit(1);
}
if ((rc = ioctl(fd, TUBOCMD, TC_EWRITE))) {
printf("ioctl(%d, %d, %d) failed with errno %d (%s)\n",
fd, TUBOCMD, TC_EWRITE, errno,
strerror(errno));
exit(1);
}
if ((rc = ioctl(fd, TUBICMD, TC_READMOD))) {
printf("ioctl(%d, %d, %d) failed with errno %d (%s)\n",
fd, TUBICMD, TC_READMOD, errno,
strerror(errno));
exit(1);
}
if ((rc = write(fd, Hello, sizeof Hello)) != sizeof Hello) {
printf("write(%d, ..., %d) returned %d, expected %d\n",
fd, sizeof Hello, rc, sizeof Hello);
exit(1);
}
memset(buf, 0xff, sizeof buf);
if ((rc = read(fd, buf, sizeof buf)) < 0) {
printf("read(%d, ..., %d) failed with errno %d (%s)\n",
fd, sizeof buf, errno, strerror(errno));
exit(1);
}
for (i = 0; i < sizeof buf; i++) {
if (buf[i] == 0xff)
break;
}
if (rc != i) {
printf("read(%d, ..., %d) returned %d but only %d bytes"
" of buffer were altered\n",
fd, sizeof buf, rc, i);
exit(1);
}
printf("read() completed: filled %d bytes of the %d-byte buffer\n",
rc, sizeof buf);
printf("AID=0x%.2x Cursor=0x%.4x\n",
buf[0], buf[1] * 256 + buf[2]);
if (buf[0] == 0x7d) printf("ENTER key pressed\n");
else if (buf[0] == 0xf1) printf("PF1 key pressed\n");
/* etc */
return 0;
}
