Transparent ioctls Streams calls Post: 22301

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Top Forums UNIX for Advanced & Expert Users Transparent ioctls Streams calls Post 22301 by S.P.Prasad on Friday 31st of May 2002 12:49:05 AM

05-31-2002

Registered User

Transparent Ioctls in Streams

Thanks a ton for your reply. What I understood that the u area is outside the scope of Stream's module except to its open and close modules.

By stating "The related data is sent in message pairs exchanged between the Stream head and the module. A pair of messages is required so that each transfer can be acknowledged." - did you mean to say that :
*mblk_t->b_cont->b_rptr == *mblk_t->b_rptr ie data buffer content is same(2 Copies of data is there ) or
mblk_t->b_cont = dupb ( mblk_t )
ie mblk_t->b_datap == mblk_t->b_cont->b_datab . Kindly clarify. While transferring data from kernel space to user or vice versa the first message block is responsible for populating the ioctl's request's response as M_COPYIN or M_COPYOUT (mblk_t->b_datap->db_type member = M_COPYIN or M_COPYOUT)
Sir, does it then means that cq_addr and cq_size of copyreq structure identifies the data and its size in the user space.
Sir , kindly also guide me on the fact that if the command type is I_STR for an input / output operation on a Stream - is it that, at the timeout interval specified in ic_timout member of strioctl structure, the stream device itself responds with ETIME error . The Stream knows how to process the internal ioctl command type and loops the message block into the queue of itself.

Last edited by S.P.Prasad; 06-06-2002 at 06:41 AM..

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LEARN ABOUT OPENSOLARIS

mcopyout

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

NAME

       mcopyout - Convert an M_IOCTL or M_IOCDATA message to an M_COPYOUT

SYNOPSIS

       #include <sys/stream.h>
       #include <sys/strsun.h>

       void mcopyout(mblk_t *mp, void *private, size_t size, void *useraddr,
	     mblk_t *dp);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI).

PARAMETERS

       mp	   M_IOCTL or M_IOCDATA message.

       private	   Value to set the cq_private field of the copyreq(9S) to.

       size	   Value to set the cq_size field of the copyreq(9S) to.

       useraddr    Optionally, the value to set the cq_addr field of the copyreq(9S) to.

       dp	   Optionally, the payload to copy out.

DESCRIPTION

       The mcopyout() function converts an M_IOCTL or M_IOCDATA message into an M_COPYOUT message using the supplied arguments.

       To  convert  the  message,  mcopyout() changes the message type to M_COPYOUT, and its payload from a iocblk(9S) to a copyreq(9S). Since the
       iocblk(9S) and copyreq(9S) are designed to overlay one another, the only fields which must be updated are cq_private, cq_size, and cq_addr,
       which  are  set to the supplied values. If useraddr is passed as NULL, the M_IOCTL must be transparent and cq_addr is assigned the pointer-
       sized quantity found at mp->b_cont->b_rptr.

       If dp is not NULL, any trailing message blocks associated with mp are freed, mp->b_cont is reset to dp and dp->b_wptr is set to	dp->b_rptr
       + size. Otherwise, any trailing message blocks are unaffected.

RETURN VALUES

       None.

CONTEXT

       This function can be called from user, kernel or interrupt context.

SEE ALSO

       mcopyin(9F), copyreq(9S), iocblk(9S)

       STREAMS Programming Guide

SunOS 5.11							    9 June 2004 						      mcopyout(9F)