[ECOS] RE: Reentrancy of the ecos drivers

[Gary Thomas]

harbonne marc wrote:
> Ok, can you point me to the ecos resources management of one the drivers
> provided?

Each of the previously mentioned packages does it their own way.

Sorry, but if you need me to spend further time explaining this to you,
you'll need to arrange for a support contract.

> 
> Regards
> Marc
> 
> -----Message d'origine-----
> De : Gary Thomas [mailto:gary@mlbassoc.com] 
> Envoyé : mardi 18 juillet 2006 16:48
> À : harbonne marc
> Cc : ecos-discuss@ecos.sourceware.org
> Objet : Re: [ECOS] RE: Reentrancy of the ecos drivers
> 
> harbonne marc wrote:
>> The driver I speak about is the ipaq touch screen present under
>> /devs/touch/ipaq but my remark concerns also the i82559 ethernet driveror
>> any other driver, so If I understand it is the responsibility  of the
>> developer to make its own protection if he wants to share the same
> resource
>> between two or more tasks ?
>> It means that theses drivers are not re-entrant ?
> 
> There's no need for them to be.  As I said before, the upper layers handle
> such concurrency and resource management.
> 
> In the case of the network driver, there are multiple layers of networking
> stack between "user" code and the driver.  These layers handle any resource
> management.  Of course, if you don't use one of the standard stacks, then
> you'd have to solve the problem yourself.
> 
> Note: this is why such management is performed at higher layers - that way
> the individual drivers don't need to be complicated with such tasks.
> 
> The touch screen is similar - the most common use is via the MicroWindows
> package which then handles the device and provides a shared resource to
> the various threads.
> 
> What sort of reentrancy are you concerned about?
> 
>> Regards
>> Marc 
>>
>> -----Message d'origine-----
>> De : Gary Thomas [mailto:gary@mlbassoc.com] 
>> Envoyé : mardi 18 juillet 2006 14:26
>> À : harbonne marc
>> Cc : ecos-discuss@ecos.sourceware.org
>> Objet : Re: [ECOS] RE: Reentrancy of the ecos drivers
>>
>> harbonne marc wrote:
>>> Hi all,
>>>
>>>  
>>>
>>> My question is quite general, I cannot see in any ecos drivers provided
>> with
>>> the last version of ecos, a way to protect the shared resources.
>>>
>>>  
>>>
>>> As example, if you look at any display driver, we cannot see a semaphore
>>> that will protect from a second task to access to the resource by
>>> pre-empting the one which has the resource.
>>>
>>>  
>>>
>>> The only call I can see is a cyg_scheduler_lock and unlock to get/release
>>> the resource.
>>>
>>>  
>>>
>>> But in many drivers such mechanism does not exist.
>>>
>>> Can you tell me why?
>> In most cases, such resource management (if it's required) is handled
>> at a level higher than the physical device driver.
>>
>> What driver(s) are you concerned about?
>>
> 
> 


-- 
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Gary Thomas                 |  Consulting for the
MLB Associates              |    Embedded world
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