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