Re: can4linux compilation for i.mx25 under 2.6.39

[Marc Kleine-Budde <mkl@pengutronix.de>]

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On 05/30/2012 03:26 PM, Martin Kozusky wrote:
> Dne 30.5.2012 15:18, Marc Kleine-Budde napsal(a):
>> On 05/30/2012 02:50 PM, Martin Kozusky wrote:
>>>>> The best for me would be some kernel module which would just put
>>>>> the CAN
>>>>> frame into some big "from userspace available" buffer in the interrupt
>>>>> and nothing more. My app would check if there is anything new and read
>>>>> it out.
>>>>> There are around 1500/sec (at 250kbit) can frames on the bus when the
>>>>> problem arise, I think it's not that much.
>>>>
>>>> Are you writing the can frames to storage in the same thread as
>>>> receiving them?
>>>
>>>
>>> No, CAN has it's own thread, which is just making struct from can
>>> messages (reading via select() )  and writes them into another buffer.
>>> Then the main thread reads this buffer and writes to SD card. Now I
>>> changed it so that this buffer is 30MB big, so I first store all the
>>> messages into RAM, and when I don't need to record CAN frames anymore, I
>>> write all of them to card from this big buffer.
>>> But this is just limited workaround because I'm limited with the RAM
>>> size (so I had to make the buffer cyclic and just latest xxxx messages
>>> are stored, older are overwritten when the buffer is full).
>>
>> Have you setup realtime priorities for you CAN thread?
> No, I did't set up any special attributes. Do you mean I should use
> pthread_attr_setschedpolicy(ptr,SCHED_RR) or something else?

or better SCHED_FIFO for your can thread.

Marc


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