Prism Header

Linux‎ > ‎

/*

* prism.h

*

* Created on: Nov 18, 2010

* Author: cmartin

*

*/

/* INFORMATION ON PRISM HEADERS

*

* Its a bit hard to get reliable information on Prism headers

* The following information has been "gleamed" from examining

* other drivers

*

* Endianness: Prism headers are in "host" order

*

* did: values are #defined below

*

* status: 0 indicates that the parameter is supplied by the driver

* 1 indicates that the driver doesn't supply the parameter.

* if not supplied it should be ignored

*

* len: 1-4 This is the number of bytes in the data field

* In all the drivers I have looked at, this value has always been 4

*

* data: The actual value - if all bits are not used they should be zeroed

*

* The Broadcom driver PRISM header supplies:

*

* hosttime: In jiffies - for our system this is in 10ms units

*

* mactime: In micro-seconds - not much use to us, we want it in milliseconds

* a 32 bit usec timer will will role over in just over an hour.

* Drivers appear to use a 64bit counter to hold mactime internal

* the then fill the prism header with the lower 32 bits

*

* channel: Not Supplied

*

* rssi: Appears to be a signed dbm value

*

* sq: Signal quality - I think that this is something to do with the number

* of errors received

*

* signal: Should be the signal strength in dbm - but doesn't appear to be.

* I have seen some drivers use a value of 100-(signal in dbm) to

* provide a positive integer. We are getting a value of "2"

*

* noise: Not Supplied - Should be signed dbm value

*

* rate: Appears to be in units/multiples of 500Khz

*

* istx: Not Supplied - 0 = rx packet, 1 = tx packet

*

* frmlen: Length of the following frame in bytes

*

*/

#ifndef PRISM_H_

#define PRISM_H_

#include "include/typedefs.h"

#define DNAMELEN 16 // Device name length

#define PRISM_MSGCODE 0x0041 // Monitor Frame

#define PRISM_DID_HOSTTIME 0x1041 // Host time element

#define PRISM_DID_MACTIME 0x2041 // Mac time element

#define PRISM_DID_CHANNEL 0x3041 // Channel element

#define PRISM_DID_RSSI 0x4041 // RSSI element

#define PRISM_DID_SQ 0x5041 // SQ element

#define PRISM_DID_SIGNAL 0x6041 // Signal element

#define PRISM_DID_NOISE 0x7041 // Noise element

#define PRISM_DID_RATE 0x8041 // Rate element

#define PRISM_DID_ISTX 0x9041 // Is Tx frame

#define PRISM_DID_FRMLEN 0xA041 // Frame length

#define PRISM_STATUS_OK 0 // Prism Status: the associated prism_value is supplied

#define PRISM_STATUS_NO_VALUE 1 // Prism Status: the associated prism_value is NOT supplied

struct prism_value

{

uint32 did; // This has a different ID for each parameter

uint16 status; // 0 = set; 1 = not set (yes - not what you expected)

uint16 len; // length of the data (u32) used 0-4

uint32 data; // The data value

} __attribute__ ((packed));

struct prism_header

{

uint32 msgcode; // = PRISM_MSGCODE

uint32 msglen; // The length of the entire header - usually 144 bytes = 0x90

char devname[DNAMELEN]; // The name of the device that captured this packet

struct prism_value hosttime; // This is measured in jiffies - I think

struct prism_value mactime; // This is a truncated microsecond timer,

// we get the lower 32 bits of a 64 bit value

struct prism_value channel;

struct prism_value rssi;

struct prism_value sq;

struct prism_value signal;

struct prism_value noise;

struct prism_value rate;

struct prism_value istx;

struct prism_value frmlen;

char dot_11_header[];

} __attribute__ ((packed));

#endif /* PRISM_H_ */