fp_read Kernel Service

Purpose

Performs a read on an open file with arguments passed.

Syntax

#include <sys/types.h>
#include <sys/errno.h>

int fp_read (fp, buf, nbytes, ext, segflag, countp)
struct file * fp;
char * buf;
ssize_t  nbytes;
ext_t   ext;
int  segflag;
ssize_t * countp;

Parameters

Table 1. Parameters
Item	Description
`fp`	Points to a file structure returned by the `fp_open` or `fp_opendev` kernel service.
`buf`	Points to the buffer where data reads from the file is to be stored.
`nbytes`	Specifies the number of bytes to be read from the file into the buffer.
`ext`	Specifies an extension argument that for some device drivers. Its content, form, and use are determined by the individual driver.
`segflag`	Indicates in which part of memory the buffer that is specified by the `buf` parameter is located: `SYS_ADSPACE` The buffer that is specified by the `buf` parameter is in kernel memory. `USER_ADSPACE` The buffer that is specified by the `buf` parameter is in application memory.
`countp`	Points to the location where the count of bytes actually read from the file is to be returned.

Description

The fp_read kernel service is an internal interface to the function provided by the read subroutine.

Execution Environment

The fp_read kernel service can be called from the process environment only.

Return Values

Table 2. Return Values
Item	Description
0	Indicates successful completion.

If an error occurs, one of the values from the /usr/include/sys/errno.h file is returned.