netdev - Re: [PATCH V2] CAN: Add Flexcan CAN controller driver

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Message-ID: <4A6F0FC2.1060605@hartkopp.net>
Date:	Tue, 28 Jul 2009 16:48:34 +0200
From:	Oliver Hartkopp <socketcan@...tkopp.net>
To:	Sascha Hauer <s.hauer@...gutronix.de>
CC:	Socketcan-core@...ts.berlios.de,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH V2] CAN: Add Flexcan CAN controller driver

Sascha Hauer wrote:
> On Tue, Jul 28, 2009 at 04:12:10PM +0200, Oliver Hartkopp wrote:
>> Oliver Hartkopp wrote:
>>> Sascha Hauer wrote:
>>>>>> +
>>>>>> +	if (frame->can_id & CAN_RTR_FLAG)
>>>>>> +		dlc |= MB_CNT_RTR;
>>>>>> +
>>>>>> +	writel(dlc, &regs->cantxfg[TX_BUF_ID].can_dlc);
>>>>>> +	writel(can_id, &regs->cantxfg[TX_BUF_ID].can_id);
>> Are you sure, that this is correct?
> 
> Yes, I am sure, at least on my hardware.

I looked into the writel() macro which does a cpu_to_le32() to the value -
sorry that i did not check this before ...

> 
>> Indeed i wonder, if it would make sense to skip the entire struct flexcan_mb
>> approach and fiddle byte-by-byte inside the registers ...
> 
> You'll have to to 32 bit accesses to get it right on little and big
> endian.
> 
> what we can do is:
> 
> writel(can_data[0] << 24 | can_data[1] << 16 | can_data[2] << 8 | can_data[3],
> 	msg_buf + 0x8);

This looks easier to understand and makes things clear, when you look into the
specification.

Regards,
Oliver
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