Linux Kernel - Modifying a module_param variable from other drivers

[manty kuma]

Hi Valdis,
Thank you for the reply.
I am not talking about all the variables. i am talking about variables
which are declared as module_param. These variables can anyways be changed
from shell prompt using echo and cat like i mentioned in the desciption. SO
i was hoping i can do it from drivers aswell.


Regards,
Sandeep


On Fri, Nov 15, 2013 at 10:30 AM, manty kuma <mantykuma at gmail.com> wrote:

> Sorry i was supposed to reply for another mail. Did it here by mistake.
>
>
> On Fri, Nov 15, 2013 at 10:29 AM, manty kuma <mantykuma at gmail.com> wrote:
>
>> Ideally, it depends on the platform you are working. You need to discuss
>> with them for the correct approach. For Qualcomm they have some hardware
>> caled as RPU(Register protection unit). They have systems calls exposed for
>> using them. You can associtate it to the register you want protection. I
>> dont know if there is any way you could do it in Linux itself?
>>
>> Regards,
>> Sandeep
>>
>>
>> On Fri, Nov 15, 2013 at 6:03 AM, <Valdis.Kletnieks at vt.edu> wrote:
>>
>>> On Thu, 14 Nov 2013 18:32:05 +0900, manty kuma said:
>>>
>>> > I see that when we declare a variable as module_param from a driver, i
>>> can
>>> > see it listed in "/sys/module/xxx/parameters/...".
>>> >
>>> > Ex : /sys/module/usbcore/parameters/autosuspend
>>> >
>>> > we can modify and read it with echo and cat commands from terminal.
>>> >
>>> > But is there a way i can read this value from other drivers? Common
>>> sense
>>> > says it should be there because if we are able to access them from user
>>> > space, from kernel space we should definitely be able to do. Is it so?
>>> If
>>> > yes, what are the API's?
>>>
>>> It's just a variable.  Read the source and find out what it's name is.
>>> You may need an EXPORT_SYMBOL() to make it available if it isn't already.
>>> And depending on the variable and its use, you may need locking and/or
>>> atomic operations to read it.
>>>
>>> And *modifying* another module's variables is just asking for trouble,
>>> mostly because very little code is written assuming that its variables
>>> may
>>> be maliciously modified out from under it.  So consider code like:
>>>
>>> int foo_size, i;
>>> struct bar *stuff;
>>>
>>> stuff = malloc(foo_size* sizeof(struct bar));
>>>
>>> /* somebody raises the value of foo_size from outside */
>>>
>>> for (i=0; i < foo_size; i++) do_something(stuff[i]);
>>>
>>> You can see where that sort of stuff is heading....
>>>
>>
>>
>
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