hostap/testing/wireless/iw_handler-2.h

374 lines
15 KiB
C

/*
* This file define the new driver API for Wireless Extensions
*
* Version : 2 6.12.01
*
* Authors : Jean Tourrilhes - HPL - <jt@hpl.hp.com>
* Copyright (c) 2001 Jean Tourrilhes, All Rights Reserved.
*/
#ifndef _IW_HANDLER_H
#define _IW_HANDLER_H
/************************** DOCUMENTATION **************************/
/*
* Initial driver API (1996 -> onward) :
* -----------------------------------
* The initial API just sends the IOCTL request received from user space
* to the driver (via the driver ioctl handler). The driver has to
* handle all the rest...
*
* The initial API also defines a specific handler in struct net_device
* to handle wireless statistics.
*
* The initial APIs served us well and has proven a reasonably good design.
* However, there is a few shortcommings :
* o No events, everything is a request to the driver.
* o Large ioctl function in driver with gigantic switch statement
* (i.e. spaghetti code).
* o Driver has to mess up with copy_to/from_user, and in many cases
* does it unproperly. Common mistakes are :
* * buffer overflows (no checks or off by one checks)
* * call copy_to/from_user with irq disabled
* o The user space interface is tied to ioctl because of the use
* copy_to/from_user.
*
* New driver API (2001 -> onward) :
* -------------------------------
* The new driver API is just a bunch of standard functions (handlers),
* each handling a specific Wireless Extension. The driver just export
* the list of handler it supports, and those will be called apropriately.
*
* I tried to keep the main advantage of the previous API (simplicity,
* efficiency and light weight), and also I provide a good dose of backward
* compatibility (most structures are the same, driver can use both API
* simultaneously, ...).
* Hopefully, I've also addressed the shortcomming of the initial API.
*
* The advantage of the new API are :
* o Handling of Extensions in driver broken in small contained functions
* o Tighter checks of ioctl before calling the driver
* o Flexible commit strategy (at least, the start of it)
* o Backward compatibility (can be mixed with old API)
* o Driver doesn't have to worry about memory and user-space issues
* The last point is important for the following reasons :
* o You are now able to call the new driver API from any API you
* want (including from within other parts of the kernel).
* o Common mistakes are avoided (buffer overflow, user space copy
* with irq disabled and so on).
*
* The Drawback of the new API are :
* o bloat (especially kernel)
* o need to migrate existing drivers to new API
* My initial testing shows that the new API adds around 3kB to the kernel
* and save between 0 and 5kB from a typical driver.
* Also, as all structures and data types are unchanged, the migration is
* quite straightforward (but tedious).
*
* ---
*
* The new driver API is defined below in this file. User space should
* not be aware of what's happening down there...
*
* A new kernel wrapper is in charge of validating the IOCTLs and calling
* the appropriate driver handler. This is implemented in :
* # net/core/wireless.c
*
* The driver export the list of handlers in :
* # include/linux/netdevice.h (one place)
*
* The new driver API is available for WIRELESS_EXT >= 13.
* Good luck with migration to the new API ;-)
*/
/* ---------------------- THE IMPLEMENTATION ---------------------- */
/*
* Some of the choice I've made are pretty controversials. Defining an
* API is very much weighting compromises. This goes into some of the
* details and the thinking behind the implementation.
*
* Implementation goals :
* --------------------
* The implementation goals were as follow :
* o Obvious : you should not need a PhD to understand what's happening,
* the benefit is easier maintainance.
* o Flexible : it should accomodate a wide variety of driver
* implementations and be as flexible as the old API.
* o Lean : it should be efficient memory wise to minimise the impact
* on kernel footprint.
* o Transparent to user space : the large number of user space
* applications that use Wireless Extensions should not need
* any modifications.
*
* Array of functions versus Struct of functions
* ---------------------------------------------
* 1) Having an array of functions allow the kernel code to access the
* handler in a single lookup, which is much more efficient (think hash
* table here).
* 2) The only drawback is that driver writer may put their handler in
* the wrong slot. This is trivial to test (I set the frequency, the
* bitrate changes). Once the handler is in the proper slot, it will be
* there forever, because the array is only extended at the end.
* 3) Backward/forward compatibility : adding new handler just require
* extending the array, so you can put newer driver in older kernel
* without having to patch the kernel code (and vice versa).
*
* All handler are of the same generic type
* ----------------------------------------
* That's a feature !!!
* 1) Having a generic handler allow to have generic code, which is more
* efficient. If each of the handler was individually typed I would need
* to add a big switch in the kernel (== more bloat). This solution is
* more scalable, adding new Wireless Extensions doesn't add new code.
* 2) You can use the same handler in different slots of the array. For
* hardware, it may be more efficient or logical to handle multiple
* Wireless Extensions with a single function, and the API allow you to
* do that. (An example would be a single record on the card to control
* both bitrate and frequency, the handler would read the old record,
* modify it according to info->cmd and rewrite it).
*
* Functions prototype uses union iwreq_data
* -----------------------------------------
* Some would have prefered functions defined this way :
* static int mydriver_ioctl_setrate(struct net_device *dev,
* long rate, int auto)
* 1) The kernel code doesn't "validate" the content of iwreq_data, and
* can't do it (different hardware may have different notion of what a
* valid frequency is), so we don't pretend that we do it.
* 2) The above form is not extendable. If I want to add a flag (for
* example to distinguish setting max rate and basic rate), I would
* break the prototype. Using iwreq_data is more flexible.
* 3) Also, the above form is not generic (see above).
* 4) I don't expect driver developper using the wrong field of the
* union (Doh !), so static typechecking doesn't add much value.
* 5) Lastly, you can skip the union by doing :
* static int mydriver_ioctl_setrate(struct net_device *dev,
* struct iw_request_info *info,
* struct iw_param *rrq,
* char *extra)
* And then adding the handler in the array like this :
* (iw_handler) mydriver_ioctl_setrate, // SIOCSIWRATE
*
* Using functions and not a registry
* ----------------------------------
* Another implementation option would have been for every instance to
* define a registry (a struct containing all the Wireless Extensions)
* and only have a function to commit the registry to the hardware.
* 1) This approach can be emulated by the current code, but not
* vice versa.
* 2) Some drivers don't keep any configuration in the driver, for them
* adding such a registry would be a significant bloat.
* 3) The code to translate from Wireless Extension to native format is
* needed anyway, so it would not reduce significantely the amount of code.
* 4) The current approach only selectively translate Wireless Extensions
* to native format and only selectively set, whereas the registry approach
* would require to translate all WE and set all parameters for any single
* change.
* 5) For many Wireless Extensions, the GET operation return the current
* dynamic value, not the value that was set.
*
* This header is <net/iw_handler.h>
* ---------------------------------
* 1) This header is kernel space only and should not be exported to
* user space. Headers in "include/linux/" are exported, headers in
* "include/net/" are not.
*
* Mixed 32/64 bit issues
* ----------------------
* The Wireless Extensions are designed to be 64 bit clean, by using only
* datatypes with explicit storage size.
* There are some issues related to kernel and user space using different
* memory model, and in particular 64bit kernel with 32bit user space.
* The problem is related to struct iw_point, that contains a pointer
* that *may* need to be translated.
* This is quite messy. The new API doesn't solve this problem (it can't),
* but is a step in the right direction :
* 1) Meta data about each ioctl is easily available, so we know what type
* of translation is needed.
* 2) The move of data between kernel and user space is only done in a single
* place in the kernel, so adding specific hooks in there is possible.
* 3) In the long term, it allows to move away from using ioctl as the
* user space API.
*
* So many comments and so few code
* --------------------------------
* That's a feature. Comments won't bloat the resulting kernel binary.
*/
/***************************** INCLUDES *****************************/
#include <linux/wireless.h> /* IOCTL user space API */
/***************************** VERSION *****************************/
/*
* This constant is used to know which version of the driver API is
* available. Hopefully, this will be pretty stable and no changes
* will be needed...
* I just plan to increment with each new version.
*/
#define IW_HANDLER_VERSION 2
/**************************** CONSTANTS ****************************/
/* Special error message for the driver to indicate that we
* should do a commit after return from the iw_handler */
#define EIWCOMMIT EINPROGRESS
/* Flags available in struct iw_request_info */
#define IW_REQUEST_FLAG_NONE 0x0000 /* No flag so far */
/* Type of headers we know about (basically union iwreq_data) */
#define IW_HEADER_TYPE_NULL 0 /* Not available */
#define IW_HEADER_TYPE_CHAR 2 /* char [IFNAMSIZ] */
#define IW_HEADER_TYPE_UINT 4 /* __u32 */
#define IW_HEADER_TYPE_FREQ 5 /* struct iw_freq */
#define IW_HEADER_TYPE_POINT 6 /* struct iw_point */
#define IW_HEADER_TYPE_PARAM 7 /* struct iw_param */
#define IW_HEADER_TYPE_ADDR 8 /* struct sockaddr */
/* Handling flags */
/* Most are not implemented. I just use them as a reminder of some
* cool features we might need one day ;-) */
#define IW_DESCR_FLAG_NONE 0x0000 /* Obvious */
/* Wrapper level flags */
#define IW_DESCR_FLAG_DUMP 0x0001 /* Not part of the dump command */
#define IW_DESCR_FLAG_EVENT 0x0002 /* Generate an event on SET */
#define IW_DESCR_FLAG_RESTRICT 0x0004 /* GET request is ROOT only */
/* Driver level flags */
#define IW_DESCR_FLAG_WAIT 0x0100 /* Wait for driver event */
/****************************** TYPES ******************************/
/* ----------------------- WIRELESS HANDLER ----------------------- */
/*
* A wireless handler is just a standard function, that looks like the
* ioctl handler.
* We also define there how a handler list look like... As the Wireless
* Extension space is quite dense, we use a simple array, which is faster
* (that's the perfect hash table ;-).
*/
/*
* Meta data about the request passed to the iw_handler.
* Most handlers can safely ignore what's in there.
* The 'cmd' field might come handy if you want to use the same handler
* for multiple command...
* This struct is also my long term insurance. I can add new fields here
* without breaking the prototype of iw_handler...
*/
struct iw_request_info
{
__u16 cmd; /* Wireless Extension command */
__u16 flags; /* More to come ;-) */
};
/*
* This is how a function handling a Wireless Extension should look
* like (both get and set, standard and private).
*/
typedef int (*iw_handler)(struct net_device *dev, struct iw_request_info *info,
union iwreq_data *wrqu, char *extra);
/*
* This define all the handler that the driver export.
* As you need only one per driver type, please use a static const
* shared by all driver instances... Same for the members...
* This will be linked from net_device in <linux/netdevice.h>
*/
struct iw_handler_def
{
/* Number of handlers defined (more precisely, index of the
* last defined handler + 1) */
__u16 num_standard;
__u16 num_private;
/* Number of private arg description */
__u16 num_private_args;
/* Array of handlers for standard ioctls
* We will call dev->wireless_handlers->standard[ioctl - SIOCSIWNAME]
*/
iw_handler * standard;
/* Array of handlers for private ioctls
* Will call dev->wireless_handlers->private[ioctl - SIOCIWFIRSTPRIV]
*/
iw_handler * private;
/* Arguments of private handler. This one is just a list, so you
* can put it in any order you want and should not leave holes...
* We will automatically export that to user space... */
struct iw_priv_args * private_args;
/* In the long term, get_wireless_stats will move from
* 'struct net_device' to here, to minimise bloat. */
};
/* ----------------------- WIRELESS EVENTS ----------------------- */
/*
* Currently we don't support events, so let's just plan for the
* future...
*/
/*
* A Wireless Event.
*/
// How do we define short header ? We don't want a flag on length.
// Probably a flag on event ? Highest bit to zero...
struct iw_event
{
__u16 length; /* Lenght of this stuff */
__u16 event; /* Wireless IOCTL */
union iwreq_data header; /* IOCTL fixed payload */
char extra[0]; /* Optional IOCTL data */
};
/* ---------------------- IOCTL DESCRIPTION ---------------------- */
/*
* One of the main goal of the new interface is to deal entirely with
* user space/kernel space memory move.
* For that, we need to know :
* o if iwreq is a pointer or contain the full data
* o what is the size of the data to copy
*
* For private IOCTLs, we use the same rules as used by iwpriv and
* defined in struct iw_priv_args.
*
* For standard IOCTLs, things are quite different and we need to
* use the stuctures below. Actually, this struct is also more
* efficient, but that's another story...
*/
/*
* Describe how a standard IOCTL looks like.
*/
struct iw_ioctl_description
{
__u8 header_type; /* NULL, iw_point or other */
__u8 token_type; /* Future */
__u16 token_size; /* Granularity of payload */
__u16 min_tokens; /* Min acceptable token number */
__u16 max_tokens; /* Max acceptable token number */
__u32 flags; /* Special handling of the request */
};
/* Need to think of short header translation table. Later. */
/**************************** PROTOTYPES ****************************/
/*
* Functions part of the Wireless Extensions (defined in net/core/wireless.c).
* Those may be called only within the kernel.
*/
/* First : function strictly used inside the kernel */
/* Handle /proc/net/wireless, called in net/code/dev.c */
extern int dev_get_wireless_info(char * buffer, char **start, off_t offset,
int length);
/* Handle IOCTLs, called in net/code/dev.c */
extern int wireless_process_ioctl(struct ifreq *ifr, unsigned int cmd);
/* Second : functions that may be called by driver modules */
/* None yet */
#endif /* _LINUX_WIRELESS_H */