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VK7AX > LINHAM 21.06.08 01:56l 137 Lines 4074 Bytes #999 (0) @ WW
BID : VK7AX-2106DU
Read: GUEST
Subj: Re: [PATCH] ax25.h unsigned long type for ax25 timers
Path: IZ3LSV<IK2XDE<DB0RES<ON0BEL<VK7AX
Sent: 080621/0003Z @:VK7AX.#ULV.TAS.AUS.OC #:47733 [Ulverstone] FBB7.00g $:VK7A
From: VK7AX@VK7AX.#ULV.TAS.AUS.OC
To : LINHAM@WW
From: Bernard Pidoux F6BVP <f6bvp(AT)free.fr>
Date: Fri, 20 Jun 2008 15:17:39 +0200
To: Bernard Pidoux <bpidoux(AT)free.fr>
CC: David Miller <davem(AT)davemloft.net>, ralf(AT)linux-mips.org,
linux-hams(AT)vger.kernel.org, netdev(AT)vger.kernel.org
There have been in the past already some modifications of
ax25_info_struct and the old one was renamed deprecated.
/* this will go away. Please do not export to user land */
struct ax25_info_struct_deprecated {
unsigned int n2, n2count;
unsigned int t1, t1timer;
unsigned int t2, t2timer;
unsigned int t3, t3timer;
unsigned int idle, idletimer;
unsigned int state;
unsigned int rcv_q, snd_q;
};
Three new items were included :
...
unsigned int vs, vr, va, vs_max;
unsigned int paclen;
unsigned int window;
};
At the same time case SIOCAX25GETINFOOLD:
was added in ax25_ioctl()
and would trigger a warning message.
/* old structure? */
if (cmd == SIOCAX25GETINFOOLD) {
static int warned = 0;
if (!warned) {
printk(KERN_INFO "%s uses old SIOCAX25GETINFO\n",
current->comm);
warned=1;
}
if (copy_to_user(argp, &ax25_info, sizeof(struct ax25_info_struct_deprecated))) {
res = -EFAULT;
break;
}
} else {
if (copy_to_user(argp, &ax25_info, sizeof(struct ax25_info_struct))) {
res = -EINVAL;
break;
}
}
res = 0;
break;
Here is my question :
Can't we remove the probably quite old ax25_info_struct_deprecated
structure, and rename the present ax25_info_struct,
ax25_info_struct_deprecated, then create the new ax25_info_struct
with resized timers unsigned long ?
The second solution is to declare a new structure
* new ax25 info struct */
struct ax25_info_long_timers_struct {
unsigned int n2, n2count;
unsigned long t1, t1timer;
unsigned long t2, t2timer;
unsigned long t3, t3timer;
unsigned long idle, idletimer;
unsigned int state;
unsigned int rcv_q, snd_q;
unsigned int vs, vr, va, vs_max;
unsigned int paclen;
unsigned int window;
};
adding another case SIOCAX25GETNEWINFO
that would be defined
#define SIOCAX25GETNEWINFO (SIOCPROTOPRIVATE+14)
and trigger warning message by calls to SIOCAX25GETINFOOLD and
SIOCAX25GETINFO.
It that the right way to do it ?
Bernard, f6bvp
Bernard Pidoux wrote:
> David,
>
> Your explanation is perfectly clear and I understand the problem now.
> Thank you very much for taking the time to explain me that.
>
> Bernard Pidoux
>
>
>
>
> David Miller wrote:
>> From: Bernard Pidoux <bpidoux(AT)free.fr>
>> Date: Thu, 19 Jun 2008 18:28:46 +0200
>>
>>> Unfortunately I don't quite understand exactly why a structure
>>> in user space cannot be changed.
>>
>> Because there are userland binaries already compiled out there using
>> the current structure layout. If we change the kernel, those binaries
>> stop using a datastructure that matches what the kernel is using.
>> Such binaries will break.
>>
>> In generic, because of this, you can never change the layout of a
>> data structure exported to userland as a kernel interface.
>>
>>
> --
--
******************************************************************
ABOVE IS A CROSS POST TO THE PACKET RADIO NETWORK IN AN EFFORT TO
PROMOTE FURTHER INTEREST IN HAM SOFTWARE USING LINUX OPERATING
SYSTEMS AND PACKET RADIO
Courtesy Tony VK7AX VK7AX(AT)VK7AX.#ULV.TAS.AUS.OC
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