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When opening a device, loop over the alternate devices list in the
worker process instead of the helper process. It is simpler this way
and allows the worker to properly log which device is being used.

/*	$OpenBSD: utils.c,v 1.7 2020/01/23 05:40:09 ratchov Exp $	*/
/*
 * Copyright (c) 2003-2012 Alexandre Ratchov <alex@caoua.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */
/*
 * log_xxx() routines are used to quickly store traces into a trace buffer.
 * This allows traces to be collected during time sensitive operations without
 * disturbing them. The buffer can be flushed on standard error later, when
 * slow syscalls are no longer disruptive, e.g. at the end of the poll() loop.
 */
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include "utils.h"

/*
 * log buffer size
 */
#define LOG_BUFSZ	8192

/*
 * store a character in the log
 */
#define LOG_PUTC(c) do {			\
	if (log_used < LOG_BUFSZ)		\
		log_buf[log_used++] = (c);	\
} while (0)

char log_buf[LOG_BUFSZ];	/* buffer where traces are stored */
unsigned int log_used = 0;	/* bytes used in the buffer */
unsigned int log_sync = 1;	/* if true, flush after each '\n' */

/*
 * write the log buffer on stderr
 */
void
log_flush(void)
{
	if (log_used == 0)
		return;
	write(STDERR_FILENO, log_buf, log_used);
	log_used = 0;
}

/*
 * store a string in the log
 */
void
log_puts(char *msg)
{
	char *p = msg;
	int c;

	while ((c = *p++) != '\0') {
		LOG_PUTC(c);
		if (log_sync && c == '\n')
			log_flush();
	}
}

/*
 * store a hex in the log
 */
void
log_putx(unsigned long num)
{
	char dig[sizeof(num) * 2], *p = dig, c;
	unsigned int ndig;

	if (num != 0) {
		for (ndig = 0; num != 0; ndig++) {
			*p++ = num & 0xf;
			num >>= 4;
		}
		for (; ndig != 0; ndig--) {
			c = *(--p);
			c += (c < 10) ? '0' : 'a' - 10;
			LOG_PUTC(c);
		}
	} else
		LOG_PUTC('0');
}

/*
 * store an unsigned decimal in the log
 */
void
log_putu(unsigned long num)
{
	char dig[sizeof(num) * 3], *p = dig;
	unsigned int ndig;

	if (num != 0) {
		for (ndig = 0; num != 0; ndig++) {
			*p++ = num % 10;
			num /= 10;
		}
		for (; ndig != 0; ndig--)
			LOG_PUTC(*(--p) + '0');
	} else
		LOG_PUTC('0');
}

/*
 * store a signed decimal in the log
 */
void
log_puti(long num)
{
	if (num < 0) {
		LOG_PUTC('-');
		num = -num;
	}
	log_putu(num);
}

/*
 * abort program execution after a fatal error
 */
void
panic(void)
{
	log_flush();
	(void)kill(getpid(), SIGABRT);
	_exit(1);
}

/*
 * allocate 'size' bytes of memory (with size > 0). This functions never
 * fails (and never returns NULL), if there isn't enough memory then
 * abort the program.
 */
void *
xmalloc(size_t size)
{
	void *p;

	p = malloc(size);
	if (p == NULL) {
		log_puts("failed to allocate ");
		log_putx(size);
		log_puts(" bytes\n");
		panic();
	}
	return p;
}

/*
 * free memory allocated with xmalloc()
 */
void
xfree(void *p)
{
#ifdef DEBUG
	if (p == NULL) {
		log_puts("xfree with NULL arg\n");
		panic();
	}
#endif
	free(p);
}

/*
 * xmalloc-style strdup(3)
 */
char *
xstrdup(char *s)
{
	size_t size;
	void *p;

	size = strlen(s) + 1;
	p = xmalloc(size);
	memcpy(p, s, size);
	return p;
}

/*
 * copy and append the given string to the name list
 */
void
namelist_add(struct name **list, char *str)
{
	struct name *n;
	size_t size;

	size = strlen(str) + 1;
	n = xmalloc(sizeof(struct name) + size);
	memcpy(n->str, str, size);
	n->next = *list;
	*list = n;
}

void
namelist_clear(struct name **list)
{
	struct name *n;

	while ((n = *list) != NULL) {
		*list = n->next;
		xfree(n);
	}
}

char *
namelist_byindex(struct name **list, unsigned int idx)
{
	struct name *n;

	n = *list;
	while (1) {
		if (n == NULL)
			return NULL;
		if (idx == 0)
			break;
		n = n->next;
		idx--;
	}
	return n->str;
}