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Full Discussion: Entry Points Routine
Top Forums Programming Entry Points Routine Post 30343 by S.P.Prasad on Monday 21st of October 2002 08:49:33 AM
Old 10-21-2002
As originally posted by Perderabo
"No there no exception for streams-based character drivers. "

Following is the cdevsw structure that we are using for developing stream device drivers in Sun and Sco unix Servers.
strcut cdevsw {
int (*d_open)( );
int (*d_close)( );
int (*d_read)( );
int (*d_write)( );
int (*d_ioctl)( );
struct tty *d_ttys ;
strcut streamtab *d_str;
char *d_name ;
};
Streams drivers have some similarites with character device drivers. A Stream driver may include init, start , halt and intr entry points.They must include open and close entry points.In addition, there are entry points that are specific to Streams driver: read and write queue service (xxsrv) read and write queue put functions.The put entry points are required with exception of the read side of a driver.The service entry points are optional.The put and service entry points are associated with each queue, and since each module and driver has two queues, each module and driver may have two put and two service entry points.The put routine is called to place a message on a queue and perform any processing that must be done immediately.The Stream head converts a write system call into a message and invokes the put routine for downstream module's write queue.This routine examines the message, performs any processing and either passes the message downstream or places it on its own queue for later processing.The Stream Device driver on the write side must provide a put entry point that may be called by the upstream module to pass message message down the stream.It may provide a write side service routine.On the read side the interrupt or poll takes the data from device and passes it to the driver's read queue or any module upstream.
.....
.....
int xxopen(),xxclose(),...... ;
static struct qinit rinit = { NULL , NULL , xxopen,xxclose,.......} ;
static struct qinit winit = { xxput, xxsrv,NULL,.......};
strcut streamtab xxinfo = {&rinit,&winit,.......};
The qinit structure contians the info for read and write queues.

I do hope I justify my stand quiet clear and sound now.The read and write queue need to be intialized.But I need a bit more of explanation.As in reference to ioctl , I think the context in which it is called is blockable but in case of streams the ioctls are transparent.That's all I know.
 

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LEARN ABOUT OSF1

strmod_del

strmod_del(2)							System Calls Manual						     strmod_del(2)

NAME

       strmod_del - Deletes STREAMS modules and drivers

SYNOPSIS

       #include <sys/stream.h> int strmod_del (      dev_t devno,      struct streamtab *streamtab,	 struct streamadm *streamadm);

PARAMETERS

       The  device number (cdevsw slot) to use when removing a STREAMS driver.	This parameter is ignored for modules.	A pointer to the streamtab
       structure that contains the entry points.  The actual streamtab structure has to be allocated permanently in the driver's  data	space  (as
       specified  by System V Release 3.2).  A pointer to the streamadm structure that contains the administration parameters for the STREAMS mod-
       ule or driver.  The actual streamadm structure is needed only for the duration of the call.  It does not have to be  allocated  permanently
       by  the	caller.  The sa_version field must be either OSF_STREAMS_10 or OSF_STREAMS_11, and the sa_flags field must be either STR_IS_DEVICE
       or STR_IS_MODULE.

DESCRIPTION

       The strmod_del() interface is used to remove configured STREAMS modules and drivers from the kernel.  Specifically, it allows STREAMS driv-
       ers to remove entry points in character device switch tables.  Modules are removed from the STREAMS modules switch.

       When removing a driver only, strmod_del() takes a device number, which is used to determine the device switch slot for the entry points.

       The streamtab parameter is a pointer to a traditional (System V Release 3.2) streamtab structure.  The structure contains pointers to entry
       points for the module's read and write queue routines.

       The streamadm parameter points to a streamadm structure.  The streamadm structure provides additional information that  is  required  under
       Tru64 UNIX.

NOTES

       The device number can be constructed from the major number through the makedev macro, which is defined in /usr/include/sys/types.h.

RETURN VALUES

       Upon  successful  completion, strmod_del() returns 0.  Otherwise, it returns one of the following values: The sa_version or sa_flags fields
       in the streamadm structure are not set correctly.  The entry is in use and cannot be removed.  The entry to be removed is not  found.   The
       devno is out of range, or the devsw entry was not in use.

RELATED INFORMATION

       Data Structures: streamadm(4).

       Routines: strmod_add(2).  delim off

																     strmod_del(2)
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