makedevice(D3)

NAME
     makedevice - make device number from major and minor numbers

SYNOPSIS
     #include <sys/types.h>
     #include <sys/ddi.h>
     dev_t makedevice(major_t majnum, minor_t minnum);

   Arguments
     majnum    Major number.

     minnum    Minor number.

DESCRIPTION
     The makedevice function creates a device number from major and minor
     device numbers.

   Return Values
     The device number, containing both the major number and the minor number,
     is returned.  No validation of the major or minor numbers is performed.

USAGE
     makedevice should be used to create device numbers so that the driver
     will port easily to releases that treat device numbers differently.

   Level
     Initialization, Base or Interrupt.

   Synchronization Constraints
     Does not sleep.

     Driver-defined basic locks, read/write locks, and sleep locks may be held
     across calls to this function.

   Singlethreaded Example
     In the following example, makedevice is used to create the device number
     selected during a clone open.  If the CLONEOPEN flag is set (line 9), we
     search through the list of minor devices looking for one that is
     available (lines 10-11).  If we find an unused minor, we break off the
     search, create a new device number, and store it in the memory location
     pointed to by devp (line 15).  If no unused minor was found, we return
     the error ENXIO.

     1  xxxopen(q, devp, oflag, sflag, crp)
     2    queue_t *q;
     3    dev_t *devp;
     4    int oflag;
     5    int sflag;
     6    cred_t *crp;
     7  {
     8    minor_t minnum;
     9    if (sflag == CLONEOPEN) {
     10        for (minnum = 0; minnum < XXXMAXMIN; minnum++)
     11            if (!INUSE(minnum))
     12                break;
     13        if (minnum >= XXXMAXMIN)
     14            return(ENXIO);
     15            SETINUSE(minnum);
     16        *devp = makedevice(getemajor(*devp), minnum);
     17    }
         ...

   Multithreaded Example
     In the following example, makedevice is used to create the device number
     selected during a clone open.  If the CLONEOPEN flag is set (line 11), we
     lock the list of minor devices (line 12) and search through the list,
     looking for a minor device that is available (lines 13-14).  If we find
     an unused minor, we break off the search, mark the minor as being in use
     (line 20), unlock the list, create a new device number, and store it in
     the memory location pointed to by devp (line 22).  If no unused minor was
     found, we unlock the list and return the error ENXIO.

     1  xxxopen(q, devp, oflag, sflag, crp)
     2    queue_t *q;
     3    dev_t *devp;
     4    int oflag;
     5    int sflag;
     6    cred_t *crp;
     7  {
     8    minor_t minnum;
     9    int pl;
     10    extern lock_t *xxxminlock;
     11    if (sflag == CLONEOPEN) {
     12        pl = LOCK(xxxminlock, plstr);
     13        for (minnum = 0; minnum < XXXMAXMIN; minnum++)
     14            if (!INUSE(minnum))
     15                break;
     16        if (minnum >= XXXMAXMIN) {
     17            UNLOCK(xxxminlock, pl);
     18            return(ENXIO);
     19        } else {
     20            SETINUSE(minnum);
     21            UNLOCK(xxxminlock, pl);
     22            *devp = makedevice(getemajor(*devp), minnum);
     23        }
     24    }
             ...

REFERENCES
     getemajor(D3), geteminor(D3), getmajor(D3), getminor(D3)