[okl4-developer] Sharing a driver between vservers

[Geoffrey Lee]

On Mon, Jul 14, 2008 at 01:46:30PM +1000, Jamie Lennox wrote:
> Thanks Geoffrey,
>

Hi Jamie

> I suppose my problem is that i need to keep the system extensible, hence  
> the seperation of keyboard and mouse on functional boundaries.
>
> Can you elaborate on what you mean by
>
> pair up the vserver with the appropriate driver in the platform 
> description file
>
> If both vservers specify the same driver instance in the machine.py file  
> then they are linked seperatly and they will not share variables.  
> Linking to the same instance is the best way i can see to accomplish 
> this.


I meant that the driver can be shared between two vservers.  Of course
you may need some appropriate means of synchronization, such as a lock
in shared memory.  The system construction is a design trade-off
and may depend on the specific use case for your application.

>
> Jamie
>
>

	-gl

>
>
> Geoffrey Lee wrote:
>> On Fri, Jul 11, 2008 at 12:05:37PM +1000, Jamie Lennox wrote:
>>   
>>> Hi,
>>>
>>>     
>>
>> Hi Jamie
>>
>>   
>>> My situation is i'm trying to write okl4 drivers that will handle a  
>>> keyboard and mouse in x86. Too make it expendable i have my vkeyboard 
>>> and vmouse servers. However in the case of PS/2 both are run through 
>>> the same 8042 chip. This means i need some form of lock when they are 
>>> operating.
>>>
>>> My understanding is that there is a single thread per vserver and the 
>>> vserver are linked against each other so can call each other directly 
>>> (no ipc). Meaning if i linked vkeyboard and vmouse against the same  
>>> driver then i am linking against different instances of the same 
>>> driver and so cannot share a lock that way.
>>>     
>>
>> Yes, they would be different instances in this scenario.
>>
>>   
>>> My question i suppose, is there some way to link both vservers to the 
>>> same 8042 driver instance so i can do my own synchronization?
>>>     
>>
>> Yes, this should be possible.  You pair up the vserver with the 
>> appropriate driver in the platform description file.  
>
>> I realise i can create a memsection with a lock and pass this to both  
>> drivers, however this problem is really only applicable in this case 
>> and so i would prefer not to do it that way.
>>
>> I suppose i can use the naming server to share a memory section, but i  
>> understand this is being phased out in favour of elfweaver.
>>
>>   
>>
>> It may be possible to use Ipc() or similar to do synchronization.   
>> Another way, as you have noted, is to create a shared memory region  
>> that both servers have access to do synchronization in that region.
>>
>> One option may be to divide it at the boundary of the device rather
>> than functionality.  For example rather than having vkeyboard and
>> vmouse maybe have one vinput instead.
>>
>>   
>>> I'm not sure if i can do it in elfweaver as i dont want the memory if 
>>> neither driver is employed, and i dont want it created twice in the  
>>> instance of both (and would prefer not to hack it up to do checks in 
>>> the root of the build system).
>>>
>>> Those are my options i know of. Is there another (nicer) way?
>>>
>>> Jamie.
>>>
>>> PS. Still wondering about using something other the device_if.di for  
>>> creating drivers.
>>>
>>>     
>>
>> device_if.di is intended to serve as a base that is common across
>> different types of device drivers.  Some devices are specific.  In this
>> case the best way is to have a null implementation of the call.  Is
>> there any strong reason why you would prefer not to use device_if?
>>
>> 	-gl
>>
>>   
>>> _______________________________________________
>>> Developer mailing list
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>>> https://lists.okl4.org/mailman/listinfo/developer
>>>
>>>     
>>
>>   
>
>

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