PRINTF_BUFFER_SIZE
printf_buffer = kmem_alloc(PRINTF_BUFFER_SIZE, KM_NOSLEEP);
len = snprintf(printf_buffer, PRINTF_BUFFER_SIZE, "%i ", -err);
KASSERT(len < PRINTF_BUFFER_SIZE);
ret = vsnprintf(printf_buffer+len, PRINTF_BUFFER_SIZE-len, fmt, ap);
KASSERT(len + ret < PRINTF_BUFFER_SIZE);
kmem_free(printf_buffer, PRINTF_BUFFER_SIZE);
printf_buffer = malloc(PRINTF_BUFFER_SIZE, M_DEVBUF, M_NOWAIT);
ret = vsnprintf(printf_buffer, PRINTF_BUFFER_SIZE, fmt, ap);
KASSERT(ret < PRINTF_BUFFER_SIZE);