On Thu, Nov 18, 2010 at 11:23:35AM +0000, Alan Cox wrote:

Example: running a boot script on /dev/console and after fsck sulogin has to called to be able to asked the system admin. Now the question is which console device the system admin is waiting in front of (before /dev/ttyS0 or /dev/tty3270 or whatever).

I'm aware of. For using tty devices of the system console it requires to have e.g. with my patch:

bash> cat /proc/tty/consoles tty0 -WU (ECp) 4:7

the `W' flag for write and the major:minor pair, beside this the `U' flag indicates the tty can do an unblank operation, the `-' shows that there is no read operation (never seen such a console tty). On an other system here I see:

bash> cat /proc/tty/consoles ttyS0 -W- (ECp) 4:64 tty0 -WU (Ep) 4:1

which I'm using in user space with

dev_t dev = 0; FILE * fc;

if ((fc = fopen("/proc/tty/consoles", "r"))) { char fbuf[16]; int maj, min; while ((fscanf(fc, "%*s %*s (%[^)]) %d:%d", &fbuf[0], &maj, &min) == 3))
{ if (!strchr(fbuf, 'E')) continue; if (strchr(fbuf, 'C')) { dev = makedev(maj, min); break; } } fclose(fc); }

to detect the primary console device here.

Werner