bit manipulation Post: 302716129

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Top Forums Programming bit manipulation Post 302716129 by Don Cragun on Tuesday 16th of October 2012 03:34:48 AM

10-16-2012

Registered User

There is certainly no reason to #define TI_ZN to two different values (unless there are conditional tests to choose one setting over another based on the compilation environment) unless you're trying to confuse someone reading your source code.

Sometimes it makes sense when defining masks for bit fields or defining various parts of a value that contains bit fields to make it easier to understand the individual fields being set. For example you might find something like:

Code:

/* File type */
#define S_IFMT          (017<<12)         /* file type mask */
#define S_IFIFO         (001<<12)         /* named pipe (fifo) */
#define S_IFCHR         (002<<12)         /* character special */
#define S_IFDIR         (004<<12)         /* directory */
#define S_IFBLK         (006<<12)         /* block special */
#define S_IFREG         (010<<12)         /* regular */
#define S_IFLNK         (012<<12)         /* symlink */
#define S_IFSOCK        (014<<12)         /* socket */

on some systems in <sys/stat.h>.

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scsi_find_sense_descr

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

NAME

       scsi_find_sense_descr - find descriptor in SCSI sense data

SYNOPSIS

       #include <sys/scsi/scsi.h>

       uint8_t *scsi_find_sense_descr(uint8_t *sense_buffer, int sense_buf_len,
	    int req_descr_type);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI).

PARAMETERS

       sense_buffer	 Pointer  to  a buffer containing SCSI descriptor sense data. The data is expected in wire format starting at the response
			 code.

       sense_buf_len	 Integer that contains the length of sense buffer in bytes.

       req_descr_type	 Integer that contains the descriptor type value for the desired sense descriptor.

DESCRIPTION

       The scsi_find_sense_descr() function is used to obtain a pointer to a specific descriptor  type,  specified  by	req_descr_type,  within  a
       descriptor  sense buffer. Before returning the pointer, scsi_find_sense_descr() verifies that the entire descriptor is present based on the
       length provided in sense_buf_len.

       Any value for req_descr_type can be requested. The following descriptor types are already defined:

	 #define DESCR_INFORMATION	   0x00
	 #define DESCR_COMMAND_SPECIFIC    0x01
	 #define DESCR_SENSE_KEY_SPECIFIC  0x02
	 #define DESCR_FRU		   0x03
	 #define DESCR_STREAM_COMMANDS	   0x04
	 #define DESCR_BLOCK_COMMANDS	   0x05
	 #define DESCR_OSD_OID		   0x06
	 #define DESCR_OSD_RESP_INTEGRITY  0x07
	 #define DESCR_OSD_ATTR_ID	   0x08

       Drivers should use scsi_validate_sense(9F) to ensure that the sense buffer contains valid descriptor sense data.

RETURN VALUES

       The scsi_find_sense_descr() function returns a pointer to a sense descriptor of the requested type if a descriptor of that type exists.	If
       no such descriptor exists, scsi_find_sense_descr() returns NULL.

CONTEXT

       The scsi_find_sense_descr() function can be called from user or interrupt context.

SEE ALSO

       scsi_ext_sense_fields(9F),    scsi_sense_asc(9F),   scsi_sense_ascq(9F),   scsi_sense_cmdspecific_uint64(9F),   scsi_sense_info_uint64(9F),
       scsi_sense_key(9F), scsi_validate_sense(9F)

SunOS 5.11							    30 Jun 2006 					 scsi_find_sense_descr(9F)