From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Thu, 01 Mar 2007 13:25:38 +0100
From: Wolfgang Grandegger <wg@domain.hid>
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Subject: Re: [Xenomai-help] CAN rt_dev_recvfrom
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To: rolandtollenaar@domain.hid
Cc: Xenomai-help@domain.hid

Roland Tollenaar wrote:
> Hi,
> 
>>> Where can I find the buffer size option in the kernel config menu? 
>>> What is the default size?
>>
>> On the first menu of the RT-Socket-CAN configuration options:
>>
>> config XENO_DRIVERS_CAN_RXBUF_SIZE
>>         depends on XENO_DRIVERS_CAN
>>         int "Size of receive ring buffers (must be 2^N)"
>>         default 1024
>>
>> Note that the messages are stored in "packed" format.
> 
> Does this mean that the buffer will store 1024 can_frame's ?

The size is usually in bytes. And as the messages are packed, the FIFO 
can hold from 1024/5 to 1024/13 messages (without time-stamp).

> If yes (or even if no) when rt_dev_recv is called, does it place the 
> last recieved message (youngest message) or the oldest (behave like a 
> FIFO) into *Buf?

It is a FIFO.

Wolfgang.