[Tinyos-devel] ctp vs other radio clients

[Philip Levis]

Well, wiring directly to ActiveMessageC would definitely be a problem!  
Regardless, it looks like ctp needs to handle busy better. I'll look  
deeper.


Phil

On Dec 6, 2008, at 9:18 AM, "Geoffrey Werner-Allen" <werner at eecs.harvard.edu 
 > wrote:

> Doesn't the queue only get put on the path if the component wires to  
> AMSenderC? What happens if, as Brany asked, something like FTSP  
> wires straight down to (essentially) CC2420ActiveMessageC.nc (which  
> it does through TimeSyncC.nc)? Anything sent below the queue won't  
> get properly serialized, right? This could cause an unexpected EBUSY  
> return in AMQueueImplP.nc if the stack is busy with somthing  
> inserted below the queue.
>
> Best,
>
> -gwa-
>
> geoffrey werner-allen :: 617.694.7261 :: www.eecs.harvard.edu/~werner
>
>
> On Sat, Dec 6, 2008 at 12:15 PM, Philip Levis <pal at cs.stanford.edu>  
> wrote:
>
> On Dec 6, 2008, at 9:05 AM, Geoffrey Werner-Allen wrote:
>
> I'm pretty sure there IS one SendState and this was my concern  
> exactly, although Om states it more clearly.
>
> Best,
>
> There is only one instance of StateC, but why does this matter?  
> Let's look at the queue code:
>
>
>        if (current >= numClients) { // queue empty
>            error_t err;
>            am_id_t amId = call AMPacket.type(msg);
>            am_addr_t dest = call AMPacket.destination(msg);
>
>            dbg("AMQueue", "%s: request to send from %hhu (%p): queue  
> empty\n", __FUNCTION__, clientId, msg);
>            current = clientId;
>
>            err = call AMSend.send[amId](dest, msg, len);
>            if (err != SUCCESS) {
>                dbg("AMQueue", "%s: underlying send failed.\n",  
> __FUNCTION__);
>                current = numClients;
>                queue[clientId].msg = NULL;
>
>            }
>            return err;
>        }
>        else {
>            dbg("AMQueue", "AMQueue: request to send from %hhu (%p):  
> queue not empty\n", clientId, msg);
>        }
>        return SUCCESS;
>
> AMQueueImplP (of which there is a single instance, it uses  
> uniqueCount() to scale its state) only calls the lower AMSend if the  
> queue is empty. If the queue is not empty, this means there is an  
> outstanding send, so it waits for the underlying sendDone.
>
> Phil
>
>
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