Re: can4linux compilation for i.mx25 under 2.6.39

[Martin Kozusky <mkozusky@kkmicro.cz>]

Dne 30.5.2012 14:40, Marc Kleine-Budde napsal(a):
> On 05/30/2012 02:29 PM, Martin Kozusky wrote:
>>> Have you debugged which component is dropping frames? Is it the hardware
>>> or the socket because your application is to slow?
>>
>> I tried to solve this 19.4.2012 (thread "CAN messages being lost on
>> i.MX25 with flexcan") and when I changed rcvbuf_size to 10000000 it
>
> Oh, I see, this conversation slipped my mind.
>
>> helped, but still sometimes few CAN frames are dropped (and many more
>> when I try to write to SD card or internal flash). So I think it's not
>> HW problem.
>> 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).

Martin

> Marc
>