minix/lib/sysutil/kputc.c

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/* 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
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* 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.
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*/
#include "sysutil.h"
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static char print_buf[80]; /* output is buffered here */
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/*===========================================================================*
* 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)) {
#define PRINTPROCS (sizeof(procs)/sizeof(procs[0]))
int procs[] = OUTPUT_PROCS_ARRAY;
static int firstprint = 1;
static cp_grant_t printgrant_buffer[PRINTPROCS];
static cp_grant_id_t printgrants[PRINTPROCS];
int p;
if(firstprint) {
/* First time? Initialize grant table;
* Grant printing processes read copy access to our
* print buffer. (So buffer can't be on stack!)
*/
cpf_preallocate(printgrant_buffer, PRINTPROCS);
for(p = 0; procs[p] != NONE; p++) {
printgrants[p] = cpf_grant_direct(procs[p], print_buf,
sizeof(print_buf), CPF_READ);
}
firstprint = 0;
}
for(p = 0; procs[p] != NONE; p++) {
/* Send the buffer to this output driver. */
m.DIAG_BUF_COUNT = buf_count;
if(GRANT_VALID(printgrants[p])) {
m.m_type = DIAGNOSTICS_S;
m.DIAG_PRINT_BUF_G = printgrants[p];
} else {
m.m_type = DIAGNOSTICS;
m.DIAG_PRINT_BUF_G = print_buf;
}
(void) _sendrec(procs[p], &m);
}
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buf_count = 0;
/* If the output fails, e.g., due to an ELOCKED, do not retry output
* at the FS as if this were a normal user-land printf(). This may
* result in even worse problems.
*/
}
if (c != 0) {
/* Append a single character to the output buffer. */
print_buf[buf_count++] = c;
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}
}