Manual Pages for UNIX Operating System command usage for man ddi_get_soft_state

Kernel Functions for Drivers                   ddi_soft_state(9F)



NAME
     ddi_soft_state,   ddi_get_soft_state,   ddi_soft_state_fini,
     ddi_soft_state_free,                    ddi_soft_state_init,
     ddi_soft_state_zalloc - driver soft state utility routines

SYNOPSIS
     #include 
     #include 



     void *ddi_get_soft_state(void *state, int item);


     void ddi_soft_state_fini(void **state_p);


     void ddi_soft_state_free(void *state, int item);


     int ddi_soft_state_init(void **state_p, size_t size, size_t n_items);


     int ddi_soft_state_zalloc(void *state, int item);


INTERFACE LEVEL
     Solaris DDI specific (Solaris DDI).

PARAMETERS
     state_p    Address of the opaque state pointer which will be
                initialized  by ddi_soft_state_init() to point to
                implementation dependent data.


     size       Size of the item which will be allocated by  sub-
                sequent calls to ddi_soft_state_zalloc().


     n_items    A hint of the  number  of  items  which  will  be
                preallocated; zero is allowed.


     state      An  opaque  pointer  to  implementation-dependent
                data that describes the soft state.


     item       The item number for the state structure;  usually
                the  instance  number  of  the associated devinfo
                node.





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Kernel Functions for Drivers                   ddi_soft_state(9F)



DESCRIPTION
     Most device drivers maintain  state  information  with  each
     instance  of  the  device  they control; for example, a soft
     copy of a device control register, a mutex that must be held
     while accessing a piece of hardware, a partition table, or a
     unit structure. These utility routines are intended to  help
     device  drivers  manage the space used by the driver to hold
     such state information.


     For example, if the driver holds the state of each  instance
     in  a  single state structure, these routines can be used to
     dynamically allocate and deallocate a separate structure for
     each  instance of the driver as the instance is attached and
     detached.


     To use the routines, the driver writer needs  to  declare  a
     state  pointer,  state_p, which the implementation uses as a
     place to hang a set  of  per-driver  structures;  everything
     else is managed by these routines.


     The routine ddi_soft_state_init() is usually called  in  the
     driver's  _init(9E) routine to initialize the state pointer,
     set the size of the soft state structure, and to  allow  the
     driver  to pre-allocate a given number of such structures if
     required.


     The routine ddi_soft_state_zalloc() is usually called in the
     driver's  attach(9E) routine.  The routine is passed an item
     number which is used to refer to the structure in subsequent
     calls to ddi_get_soft_state() and ddi_soft_state_free(). The
     item number is usually  just  the  instance  number  of  the
     devinfo  node,  obtained with ddi_get_instance(9F). The rou-
     tine attempts to allocate space for the new  structure,  and
     if  the  space  allocation  was  successful,  DDI_SUCCESS is
     returned to the caller. Returned memory is zeroed.


     A pointer to the space previously allocated for a soft state
     structure  can  be  obtained by calling ddi_get_soft_state()
     with the appropriate item number.


     The space used by  a  given  soft  state  structure  can  be
     returned  to  the  system  using ddi_soft_state_free(). This
     routine is usually called from the driver's detach(9E) entry
     point.





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Kernel Functions for Drivers                   ddi_soft_state(9F)



     The space used by all the soft state structures allocated on
     a given state pointer, together with the housekeeping infor-
     mation used by the implementation can  be  returned  to  the
     system  using  ddi_soft_state_fini().  This  routine  can be
     called from the driver's _fini(9E) routine.


     The   ddi_soft_state_zalloc(),   ddi_soft_state_free()   and
     ddi_get_soft_state()   routines  coordinate  access  to  the
     underlying data structures in an MT-safe  fashion,  thus  no
     additional locks should be necessary.

RETURN VALUES
     ddi_get_soft_state()

     NULL       The requested state structure was  not  allocated
                at the time of the call.


     pointer    The pointer to the state structure.



     ddi_soft_state_init()

     0         The allocation was successful.


     EINVAL    Either the size parameter was zero, or the state_p
               parameter was invalid.



     ddi_soft_state_zalloc()

     DDI_SUCCESS    The allocation was successful.


     DDI_FAILURE    The routine failed to  allocate  the  storage
                    required;  either  the  state  parameter  was
                    invalid, the item number was negative, or  an
                    attempt  was  made to allocate an item number
                    that was already allocated.


CONTEXT
     The ddi_soft_state_init() and  ddi_soft_state_alloc()  func-
     tions  can be called from user or kernel context only, since
     they may internally call kmem_zalloc(9F) with  the  KM_SLEEP
     flag.





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Kernel Functions for Drivers                   ddi_soft_state(9F)



     The   ddi_soft_state_fini(),    ddi_soft_state_free()    and
     ddi_get_soft_state()  routines can be called from any driver
     context.

EXAMPLES
     Example 1 Creating and Removing Data Structures


     The following example shows how the routines described above
     can  be  used  in  terms  of  the  driver  entry points of a
     character-only driver. The example concentrates on the  por-
     tions  of  the code that deal with creating and removing the
     driver's data structures.


       typedef struct {
          volatile caddr_t *csr;        /* device registers */
          kmutex_t         csr_mutex;   /* protects 'csr' field */
          unsigned int     state;
          dev_info_t       *dip;        /* back pointer to devinfo */
       } devstate_t;
       static void *statep;

       int
       _init(void)
       {
          int error;

          error = ddi_soft_state_init(&statep, sizeof (devstate_t), 0);
          if (error != 0)
                    return (error);
          if ((error = mod_install(&modlinkage)) != 0)
                    ddi_soft_state_fini(&statep);
          return (error);
       }

       int
       _fini(void)
       {
          int error;

          if ((error = mod_remove(&modlinkage)) != 0)
                    return (error);
          ddi_soft_state_fini(&statep);
          return (0);
       }

       static int
       xxattach(dev_info_t *dip, ddi_attach_cmd_t cmd)
       {
          int instance;
          devstate_t *softc;



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Kernel Functions for Drivers                   ddi_soft_state(9F)



          switch (cmd) {
          case DDI_ATTACH:
                  instance = ddi_get_instance(dip);
             if (ddi_soft_state_zalloc(statep, instance) != DDI_SUCCESS)
                     return (DDI_FAILURE);
                  softc = ddi_get_soft_state(statep, instance);
                  softc->dip = dip;
                  ...
                  return (DDI_SUCCESS);
          default:
                  return (DDI_FAILURE);
          }
       }

       static int
       xxdetach(dev_info_t *dip, ddi_detach_cmd_t cmd)
       {
          int instance;

          switch (cmd) {

          case DDI_DETACH:
                  instance = ddi_get_instance(dip);
                  ...
             ddi_soft_state_free(statep, instance);
             return (DDI_SUCCESS);

          default:
             return (DDI_FAILURE);
          }
       }

       static int
       xxopen(dev_t *devp, int flag, int otyp, cred_t *cred_p)
       {
          devstate_t *softc;
          int   instance;

          instance = getminor(*devp);
          if ((softc = ddi_get_soft_state(statep, instance)) == NULL)
                  return (ENXIO);
          ...
          softc->state |= XX_IN_USE;
          ...
          return (0);
       }


SEE ALSO
     _fini(9E),      _init(9E),      attach(9E),      detach(9E),
     ddi_get_instance(9F), getminor(9F), kmem_zalloc(9F)




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Kernel Functions for Drivers                   ddi_soft_state(9F)



     Writing Device Drivers

WARNINGS
     There is no attempt to validate the item parameter given  to
     ddi_soft_state_zalloc()  other  than  it  must be a positive
     signed integer. Therefore very large item numbers may  cause
     the  driver  to  hang  forever  waiting  for  virtual memory
     resources that can never be satisfied.

NOTES
     If necessary, a hierarchy of state structures  can  be  con-
     structed  by  embedding state pointers in higher order state
     structures.

DIAGNOSTICS
     All of the messages described below usually indicate bugs in
     the  driver and should not appear in normal operation of the
     system.

       WARNING: ddi_soft_state_zalloc: bad handle
       WARNING: ddi_soft_state_free: bad handle
       WARNING: ddi_soft_state_fini: bad handle



     The implementation-dependent information kept in  the  state
     variable is corrupt.

       WARNING: ddi_soft_state_free: null handle
       WARNING: ddi_soft_state_fini: null handle



     The routine has been passed a null or corrupt state pointer.
     Check that ddi_soft_state_init() has been called.

       WARNING: ddi_soft_state_free: item %d not in range [0..%d]



     The routine has been asked to free an item which  was  never
     allocated.  The  message  prints out the invalid item number
     and the acceptable range.












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