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dsent(9s)


NAME

  dsent - General: Defines a device driver's entry points and other
  information


SYNOPSIS

       struct dsent
       {
	 int (*d_open)();
	 int (*d_close)();
	 int (*d_strategy)();
	 int (*d_read)();
	 int (*d_write)();
	 int (*d_ioctl)();
	 int (*d_dump)();
	 int (*d_psize)();
	 int (*d_stop)();
	 int (*d_reset)();
	 int (*d_select)();
	 int (*d_mmap)();
	 int (*d_segmap)();
	 struct tty *d_ttys;
	 int d_funnel;
	 int d_bflags;
	 int d_cflags;
       };


MEMBERS

  d_open
      Specifies a pointer to an entry point for the block and character
      driver's open interface, which opens a device.

  d_close
      Specifies a pointer to an entry point for the block and character
      driver's close interface, which closes a device.

  d_strategy
      Specifies a pointer to an entry point for the block driver's strategy
      interface, which reads and writes block data.

  d_read
      Specifies a pointer to an entry point for the character driver's read
      interface, which reads characters or raw data.

  d_write
      Specifies a pointer to an entry point for the character driver's write
      interface, which writes characters or raw data.

  d_ioctl
      Specifies a pointer to an entry point for the block and character
      driver's ioctl interface, which performs special functions or I/O
      control.

  d_dump
      Specifies a pointer to an entry point for a block driver's dump
      interface, which is used for panic dumps of the system image.

  d_psize
      Specifies a pointer to an entry point for the block driver's psize
      interface, which returns the size in physical blocks of a device (disk
      partition).

  d_stop
      Specifies a pointer to an entry point for the driver's stop interface,
      which suspends other processing on behalf of the current process. You
      typically use the d_stop member only for terminal (character) drivers.

  d_reset
      Specifies a pointer to an entry point for the character driver's reset
      interface, which stops all current work and places the device connected
      to the controller in a known, quiescent state.

  d_select
      Specifies a pointer to an entry point for the character driver's select
      interface, which determines if a call to a read or write interface will
      block.

  d_mmap
      Specifies a pointer to an entry point for the character driver's mmap
      interface, which maps kernel memory to user address space.

  d_segmap
      Specifies the character driver's segmap entry point.

  d_ttys
      Specifies a pointer to the character driver's private data.

  d_funnel
      Schedules block and character device drivers onto a CPU in a
      multiprocessor configuration. You can pass the constants DEV_FUNNEL
      (funnel the device) or DEV_FUNNEL_NULL (do not funnel the device). See
      the DESCRIPTION section for more information on these constants.

  d_bflags
      Specifies a block driver's device-related and other flags.  You set
      this member to the bitwise inclusive OR of the device-related and other
      flags. One example of a device-related flag is B_TAPE.  This flag is
      set in the b_flags member of the buf structure. The B_TAPE flag
      determines whether to use delayed writes, which are not allowed for
      tape devices. For all other drivers, this member is set to the value 0
      (zero). Another flag specifies whether this character driver is an SVR4
      DDI/DKI-compliant device driver. You set this member to the B_DDIDKI
      flag to indicate that this is an SVR4 DDI/DKI-compliant device driver.

  d_cflags
      Specifies whether this character driver is an SVR4 DDI/DKI-compliant
      device driver. Set this member to the C_DDIDKI constant to indicate
      that this is an SVR4 DDI/DKI-compliant device driver.


DESCRIPTION

  The dsent data structure contains pointers to entry points for a specific
  driver's I/O services interfaces and other information. The system
  maintains a table (array) of these dsent data structures (referred to as
  the device switch table) that contains pointers to entry points for the
  associated driver's I/O services interfaces for each block and character
  mode device that the system supports.	 In addition, the table can contain
  stubs for device driver entry points for block and character mode devices
  that do not exist or entry points not used by a device driver.

  Both block and character device special files can access the same device
  driver entry. If the device driver does not support access by both block
  and character device special files, then the driver must perform the
  appropriate check in its open interface and return an error for the devices
  it does not support.

  The d_funnel member takes one of the following constants:

  DEV_FUNNEL
	  Specifies that you want to funnel the device driver because you
	  have not made it SMP safe. This means that the driver is forced to
	  execute on a single (the master) CPU.

	  Even if you funnel your device driver, you must follow the SMP
	  locking conventions when accessing kernel data structures external
	  to the driver.  Typically, you use kernel interfaces that
	  Compaqsupplies to indirectly access kernel data structures outside
	  the driver.

  DEV_FUNNEL_NULL
	  Specifies that you do not want to funnel the device driver because
	  you have made it SMP safe. This means that the driver can execute
	  on multiple CPUs. You make a device driver SMP safe by using the
	  simple or complex lock mechanism.


FILES

  <sys/conf.h>


SEE ALSO

  Kernel Interfaces: devsw_add(9r), devsw_del(9r), devsw_get(9r)

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