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

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Message-ID: <20090728145354.GX2714@pengutronix.de>
Date:	Tue, 28 Jul 2009 16:53:54 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Oliver Hartkopp <socketcan@...tkopp.net>
Cc:	Socketcan-core@...ts.berlios.de,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH V2] CAN: Add Flexcan CAN controller driver

On Tue, Jul 28, 2009 at 04:48:34PM +0200, Oliver Hartkopp wrote:
> 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.

Ok, I'll change it like this.

Sascha


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