/* -*- c -*-
 *
 * Copyright (c) 2004-2005 The Trustees of Indiana University.
 *                         All rights reserved.
 * Copyright (c) 2004-2005 The Regents of the University of California.
 *                         All rights reserved.
 * $COPYRIGHT$
 *
 * Additional copyrights may follow
 *
 * $HEADER$
 */

#include <plpa.h>
#include <errno.h>
#include <sys/syscall.h>
#include <unistd.h>

/* Cache, just to make things a little more efficient */
static PLPA_NAME(api_type_t) cache = PLPA_PROBE_UNSET;

/* The len value we find - not in public header, but used by the lib */
size_t PLPA_NAME(len) = 0;

PLPA_NAME(api_type_t) PLPA_NAME(api_probe)(void) 
{
    if (PLPA_PROBE_UNSET == cache) {
        PLPA_NAME(cpu_set_t) mask;
        int rc;
        size_t len;

        for (len = sizeof(mask); len != 0; len >>= 1) {
            rc = syscall(__NR_sched_getaffinity, 0, len, &mask);
            if (rc >= 0) {
                /* OK, kernel is happy with a get().  Validate w/ a set(). */
                /* Note that kernel may have told us the "proper" size */
                size_t tmp = (0 != rc) ? ((size_t) rc) : len;
                /* Pass mask=NULL, expect errno==EFAULT if tmp was OK as a length */
                rc = syscall(__NR_sched_setaffinity, 0, tmp, NULL);
                if ((rc < 0) && (errno == EFAULT)) {
                    cache = PLPA_PROBE_OK;
                    PLPA_NAME(len) = tmp;
                    rc = 0;
                    break;
                }
            }
            if (errno == ENOSYS) {
                break; /* No point in looping */
            }
        }
        
        if (rc >= 0) {
            /* OK */
        } else if (errno == ENOSYS) {
            /* Kernel returns ENOSYS because there is no support for
                processor affinity */
            cache = PLPA_PROBE_NOT_SUPPORTED;
        } else {
            /* Unknown! */
            cache = PLPA_PROBE_UNKNOWN;
        }
    }

    return cache;
}