esballoc man page on SmartOS

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       esballoc,  desballoc - allocate a message block using a caller-supplied

       #include <sys/stream.h>

       mblk_t *esballoc(uchar_t *base, size_t size, uint_t pri,
	    frtn_t *fr_rtnp);

       mblk_t *desballoc(uchar_t *base, size_t size, uint_t pri,
	    frtn_t *fr_rtnp);

       esballoc(): Architecture independent level 1 (DDI/DKI)

       desballoc(): Solaris DDI specific (Solaris DDI)

		  Address of caller-supplied data buffer.

		  Number of bytes in data buffer.

		  Priority of the request (no longer used).

		  Free routine data structure.

       The  esballoc()	and  desballoc()  functions  operate  identically   to
       allocb(9F),  except  that the data buffer to associate with the message
       is specified by the caller. The allocated message will  have  both  the
       b_wptr  and  b_rptr  set	 to the supplied data buffer starting at base.
       Only the buffer itself can be specified	by  the	 caller.  The  message
       block and data block header are allocated as if by allocb(9F).

       When  freeb(9F)	is  called  to free the message, the driver's message-
       freeing routine, referenced  through  the  free_rtn(9S)	structure,  is
       called with appropriate arguments to free the data buffer.

       The free_rtn(9S) structure includes the following members:

	 void (*free_func)();	  /* caller's freeing routine */
	 caddr_t free_arg;	  /* argument to free_func() */

       Instead of requiring a specific number of arguments, the free_arg field
       is defined of type caddr_t. This way, the driver can pass a pointer  to
       a structure if more than one argument is needed.

       If esballoc() was used, then free_func will be called asynchronously at
       some point after the message is no longer  referenced.  If  desballoc()
       was  used,  then	 free_func  will be called synchronously by the thread
       releasing the final reference. See freeb(9F).

       The free_func routine must not sleep, and must not access  any  dynami‐
       cally  allocated	 data  structures that could be freed before or during
       its execution.  In addition, because messages  allocated	 with  desbal‐
       loc()  are  freed in the context of the caller, free_func must not call
       another module's put procedure, or attempt to acquire a private	module
       lock  which  might be held by another thread across a call to a STREAMS
       utility routine that could free a  message  block.  Finally,  free_func
       routines	 specified  using  desballoc  may run in interrupt context and
       thus must only use synchronization primitives that include an interrupt
       priority	  returned  from  ddi_intr_get_pri(9F)	or  ddi_intr_get_soft‐
       int_pri(9F). If any of these restrictions are not followed, the	possi‐
       bility of lock recursion or deadlock exists.

       On success, a pointer to the newly allocated message block is returned.
       On failure, NULL is returned.

       The esballoc() and desballoc()  functions  can  be  called  from	 user,
       interrupt, or kernel context.

       See attributes(5) for descriptions of the following attributes:

       │Interface Stability │ Committed	      │

       allocb(9F),     ddi_intr_get_pri(9F),	 ddi_intr_get_softint_pri(9F),
       freeb(9F), datab(9S), free_rtn(9S)

       Writing Device Drivers

       STREAMS Programming Guide

				 Jan 16, 2006			  ESBALLOC(9F)

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