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esballoc(9f) [opensolaris man page]

esballoc(9F)						   Kernel Functions for Drivers 					      esballoc(9F)

NAME
esballoc, desballoc - allocate a message block using a caller-supplied buffer SYNOPSIS
#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); INTERFACE LEVEL
esballoc(): Architecture independent level 1 (DDI/DKI) desballoc(): Solaris DDI specific (Solaris DDI) PARAMETERS
base Address of caller-supplied data buffer. size Number of bytes in data buffer. pri Priority of the request (no longer used). fr_rtnp Free routine data structure. DESCRIPTION
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 desbal- loc() 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 dynamically allocated data structures that could be freed before or during its execution. In addition, because messages allocated with desballoc() 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_softint_pri(9F). If any of these restrictions are not followed, the possibility of lock recursion or deadlock exists. RETURN VALUES
On success, a pointer to the newly allocated message block is returned. On failure, NULL is returned. CONTEXT
The esballoc() and desballoc() functions can be called from user, interrupt, or kernel context. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Committed | +-----------------------------+-----------------------------+ SEE ALSO
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 SunOS 5.11 16 Jan 2006 esballoc(9F)

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esballoc(9F)						   Kernel Functions for Drivers 					      esballoc(9F)

NAME
esballoc - allocate a message block using a caller-supplied buffer SYNOPSIS
#include <sys/stream.h> mblk_t *esballoc(uchar *base, size_t size, uint_t pri, frtn_t *fr_rtnp); INTERFACE LEVEL
Architecture independent level 1 (DDI/DKI). PARAMETERS
base Address of user supplied data buffer. size Number of bytes in data buffer. pri Priority of allocation request (to be used by allocb(9F) function, called by esballoc()). fr_rtnp Free routine data structure. DESCRIPTION
esballoc() creates a STREAMS message and attaches a user-supplied data buffer in place of a STREAMS data buffer. It calls allocb(9F) to get a message and data block header only. The newly allocated message will have both the b_wptr and b_rptr set to the base of the buffer. As when using allocb(9F), the newly allocated message will have both b_wptr and b_rptr set to the base of the data buffer. The user-sup- plied data buffer, pointed to by base, is used as the data buffer for the message. When freeb(9F) is called to free the message, the driver's message freeing routine (referenced through the free_rtn structure) is called, with appropriate arguments, to free the data buffer. The free_rtn structure includes the following members: void (*free_func)(); /* user's freeing routine */ char *free_arg; /* arguments to free_func() */ Instead of requiring a specific number of arguments, the free_arg field is defined of type char *. This way, the driver can pass a pointer to a structure if more than one argument is needed. The method by which free_func is called is implementation-specific. The module writer must not assume that free_func will or will not be called directly from STREAMS utility routines like freeb(9F) which free a message block. free_func must not call another modules put procedure nor attempt to acquire a private module lock which may be held by another thread across a call to a STREAMS utility routine which could free a message block. Otherwise, the possibility for lock recursion and/or deadlock exists. free_func must not access any dynamically allocated data structure that might no longer exist when it runs. RETURN VALUES
On success, a pointer to the newly allocated message block is returned. On failure, NULL is returned. CONTEXT
esballoc() can be called from user or interrupt context. SEE ALSO
allocb(9F), freeb(9F), datab(9S), free_rtn(9S) Writing Device Drivers STREAMS Programming Guide WARNINGS
The free_func must be defined in kernel space, should be declared void and accept one argument. It has no user context and must not sleep. SunOS 5.10 23 Jun 1997 esballoc(9F)
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