Re: can4linux compilation for i.mx25 under 2.6.39

[Martin Kozusky <mkozusky@kkmicro.cz>]

Dne 30.5.2012 16:18, Marc Kleine-Budde napsal(a):
> 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.
Hello Marc,
I tried that and still when I write
dd if=/dev/zero of=/mnt/mmcblk0p1/test bs=512 count=10000 (copy 5MB to 
SD card)  around 300 CAN frames (from 68500 frames) are lost :(

Martin

> Marc
>
>