minix/lib/sysutil/kputc.c
Ben Gras 3cc092ff06 . new kernel call sysctl for generic unprivileged system operations;
now used for printing diagnostic messages through the kernel message
   buffer. this lets processes print diagnostics without sending messages
   to tty and log directly, simplifying the message protocol a lot and
   reducing difficulties with deadlocks and other situations in which
   diagnostics are blackholed (e.g. grants don't work). this makes
   DIAGNOSTICS(_S), ASYN_DIAGNOSTICS and DIAG_REPL obsolete, although tty
   and log still accept the codes for 'old' binaries. This also simplifies
   diagnostics in several servers and drivers - only tty needs its own
   kputc() now.
 . simplifications in vfs, and some effort to get the vnode references
   right (consistent) even during shutdown. m_mounted_on is now NULL
   for root filesystems (!) (the original and new root), a less awkward
   special case than 'm_mounted_on == m_root_node'. root now has exactly
   one reference, to root, if no files are open, just like all other
   filesystems. m_driver_e is unused.
2009-01-26 17:43:59 +00:00

33 lines
1.1 KiB
C

/* A server must occasionally print some message. It uses a simple version of
* printf() found in the system lib that calls kputc() to output characters.
* Printing is done with a call to the kernel, and not by going through FS.
*
* This routine can only be used by servers and device drivers. The kernel
* must define its own kputc(). Note that the log driver also defines its own
* kputc() to directly call the TTY instead of going through this library.
*/
#include "sysutil.h"
static char print_buf[DIAG_BUFSIZE]; /* output is buffered here */
/*===========================================================================*
* kputc *
*===========================================================================*/
void kputc(c)
int c;
{
/* Accumulate another character. If 0 or buffer full, print it. */
static int buf_count; /* # characters in the buffer */
message m;
if ((c == 0 && buf_count > 0) || buf_count == sizeof(print_buf)) {
sys_sysctl(SYSCTL_CODE_DIAG, print_buf, buf_count);
buf_count = 0;
}
if (c != 0) {
/* Append a single character to the output buffer. */
print_buf[buf_count++] = c;
}
}