lib/sysutil/kputc.c

   1 /* A server must occasionally print some message.  It uses a simple version of
   2  * printf() found in the system lib that calls kputc() to output characters.
   3  * Printing is done with a call to the kernel, and not by going through FS.
   4  *
   5  * This routine can only be used by servers and device drivers.  The kernel
   6  * must define its own kputc(). Note that the log driver also defines its own
   7  * kputc() to directly call the TTY instead of going through this library.
   8  */
   9
  10 #include "sysutil.h"
  11
  12 static char print_buf[80];      /* output is buffered here */
  13
  14 int kputc_use_private_grants= 0;
  15
  16 /*===========================================================================*
  17  *                              kputc                                        *
  18  *===========================================================================*/
  19 void kputc(c)
  20 int c;
  21 {
  22 /* Accumulate another character.  If 0 or buffer full, print it. */
  23   static int buf_count;         /* # characters in the buffer */
  24   message m;
  25
  26   if ((c == 0 && buf_count > 0) || buf_count == sizeof(print_buf)) {
  27 #define PRINTPROCS (sizeof(procs)/sizeof(procs[0]))
  28         int procs[] = OUTPUT_PROCS_ARRAY;
  29         static int firstprint = 1;
  30         static cp_grant_id_t printgrants[PRINTPROCS];
  31         int p;
  32
  33         if (kputc_use_private_grants)
  34         {
  35                 for (p= 0; p<PRINTPROCS; p++)
  36                         printgrants[p]= GRANT_INVALID;
  37                 firstprint= 0;
  38         }
  39         if(firstprint) {
  40                 for(p = 0; procs[p] != NONE; p++) {
  41                         printgrants[p] = GRANT_INVALID;
  42                 }
  43
  44                 firstprint = 0;
  45
  46                 /* First time? Initialize grant table;
  47                  * Grant printing processes read copy access to our
  48                  * print buffer forever. (So buffer can't be on stack!)
  49                  */
  50                 for(p = 0; procs[p] != NONE; p++) {
  51                         printgrants[p] = cpf_grant_direct(procs[p], print_buf,
  52                                 sizeof(print_buf), CPF_READ);
  53                 }
  54         }
  55
  56         for(p = 0; procs[p] != NONE; p++) {
  57                 /* Send the buffer to this output driver. */
  58                 m.DIAG_BUF_COUNT = buf_count;
  59                 if(GRANT_VALID(printgrants[p])) {
  60                         m.m_type = DIAGNOSTICS_S;
  61                         m.DIAG_PRINT_BUF_G = printgrants[p];
  62                 } else {
  63                         m.m_type = DIAGNOSTICS;
  64                         m.DIAG_PRINT_BUF_G = print_buf;
  65                 }
  66                 (void) _sendrec(procs[p], &m);
  67         }
  68
  69         buf_count = 0;
  70
  71         /* If the output fails, e.g., due to an ELOCKED, do not retry output
  72          * at the FS as if this were a normal user-land printf(). This may
  73          * result in even worse problems.
  74          */
  75   }
  76   if (c != 0) {
  77
  78         /* Append a single character to the output buffer. */
  79         print_buf[buf_count++] = c;
  80   }
  81 }