Re: usb-can device

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

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On 08/28/2012 02:18 PM, Oliver Hartkopp wrote:

[...]

>>> I found a very interesting implementation in the Bosch M_CAN specification:
>>>
>>> http://www.semiconductors.bosch.de/en/ipmodules/can/canipmodules/m_can/m_can.asp
>>>
>>> http://www.semiconductors.bosch.de/media/en/pdf/ipmodules_1/m_can/mcan_users_manual.pdf
>>>
>>> Section 2.4.3 Tx Buffer Element (page 45)
>>>
>>> ---8<---
>>>
>>> T1 Bits 31:24 MM[7:0]: Message Marker
>>>
>>> Written by CPU during Tx Buffer configuration. Copied into Tx Event FIFO
>>> element for identification of Tx message status.
>>>
>>> ---8<---
>>>
>>> So you can see in the Tx event FIFO, which marked CAN frame has been sent.
>>>
>>> This is probably enough to provide just a byte and to create an array of
>>> skb pointers which is referenced by this Message Marker. Maybe 256 markers
>>> are too much ... we could only use 8 markers IMO.
>>
>> Why not a full u32? Then you're free on the driver side to do what you
>> want with it.
> 
> 
> Yes. You're right. It's a marker - and if i personally only want to handle an
> index into an array with 8 elements with my driver it's my choice.
ACK :)

Marc

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