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DEVGETGEOM(9r)
NAME
  DEVGETGEOM - Disk: Obtains device geometry information

SYNOPSIS
  #include <io/common/devio.h>
  #include <sys/ioctl.h>


  int ioctl(
	  dev_t dev,
	  register int DEVGETGEOM,
	  caddr_t data,
	  int flag );

DESCRIPTION
  The DEVGETGEOM ioctl command obtains generic device geometry information by
  polling the underlying device driver.	 DEVGETGEOM uses the following union
  defined in the file /usr/sys/include/io/common/devio.h:

       typedef union devgeom {
	struct {
	    unsigned long   dev_size;
	    unsigned short  ntracks;
	    unsigned short  nsectors;
	    unsigned short  ncylinders;
	    unsigned long   attributes;
	    unsigned long   sector_size;
	    unsigned long   min_trans;
	    unsigned long   max_trans;
	    unsigned long   prefer_trans;
	   } geom_info;
	   unsigned char       pad[108];
       } DEVGEOMST;

  This union contains two members: a geom_info data structure and a pad array
  that allocates space to allow for future expansion. The following list
  describes the members of the geom_info structure:

  dev_size
      Specifies the total number of sectors/blocks on the device available
      for use.

  ntracks
      Specifies the number of tracks per cylinder. This number may not
      actually reflect the number of tracks per cylinder but is an estimate
      (RAID devices).

  nsectors
      Specifies an average number of sectors per track.

  ncylinders
      Specifies an average number of cylinders per track.

  attributes
      Specifies one of the following device attributes: DEVGEOM_REMOVE (a
      removable device) or DEVGEOM_DYNAMIC (a dynamic geometry device).

  sector_size
      Specifies the number of bytes in the sector.

  min_trans
      Specifies the minimum number of bytes for the transfer size.

  max_trans
      Specifies the maximum number of bytes for the transfer size.

  prefer_trans
      Specifies the preferred number of bytes for the transfer size.

EXAMPLE
  The following code example shows how a disk device driver can use the
  DEVGETGEOM ioctl command. The example uses the attributes, dev_size, and
  sector_size members of the geom_info structure.

       .
       .
       .

       cdisk_ioctl(dev_t dev, register int cmd, caddr_t data, int flag)
       {

       .
       .
       .

	       switch (cmd) {

       .
       .
       .

		   /*
		    * Disk geometry info.
		    */
       case DEVGETGEOM:
	    {
		DEVGEOMST *devgeom = (DEVGEOMST *)data;

       .
       .
       .

		bzero((caddr_t)devgeom, sizeof(DEVGEOMST));

		if(inqp->rmb)
		    devgeom->geom_info.attributes |= DEVGEOM_REMOVE;

		/*
		 * HSX00 and HSX01 FIB RAID devices are flagged
		 * as having "dynamic geometry" because the
		 * geometry of the underlying device can change
		 * depending on the configuration of units.
		 */
		if ( dd->dd_flags & SZ_DYNAMIC_GEOM != 0)
		     devgeom->geom_info.attributes |= DEVGEOM_DYNAMIC;

		/*
		 * Get disk size via read capacity command.
		 */
		read_cap_data = (DIR_READ_CAP_DATA *)
		       ccmn_get_dbuf((U32)sizeof(DIR_READ_CAP_DATA));
		if(cdisk_read_capacity(pd, read_cap_data) == 0) {
			BTOL(&read_cap_data->lbn3, nblocks);
			/*
			 * RDCAP returns the address of the last LBN.
			 * Add one to get the number of LBNs.
			 */
			devgeom->geom_info.dev_size = ++nblocks;

			/*
			 * Get the sector size.
			 */
			BTOL(&read_cap_data->block_len3, blk_len);
			devgeom->geom_info.sector_size = blk_len ;

       .
       .
       .


SEE ALSO
  ioctl Commands: DEVIOCGET(9r)

Index for Section 9

Alphabetical listing for D

Top of page