linux-kernel - Re: [PATCH v10 1/5] mtd: nand: vf610_nfc: Freescale NFC for VF610, MPC5125 and others

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Date:	Thu, 27 Aug 2015 09:47:36 -0700
From:	Brian Norris <computersforpeace@...il.com>
To:	Stefan Agner <stefan@...er.ch>
Cc:	dwmw2@...radead.org, sebastian@...akpoint.cc, robh+dt@...nel.org,
	pawel.moll@....com, mark.rutland@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	shawn.guo@...aro.org, kernel@...gutronix.de,
	boris.brezillon@...e-electrons.com, marb@...at.de,
	aaron@...tycactus.com, bpringlemeir@...il.com,
	linux-mtd@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	albert.aribaud@...ev.fr, klimov.linux@...il.com,
	Bill Pringlemeir <bpringlemeir@...ps.com>
Subject: Re: [PATCH v10 1/5] mtd: nand: vf610_nfc: Freescale NFC for VF610,
 MPC5125 and others

On Wed, Aug 26, 2015 at 06:10:05PM -0700, Stefan Agner wrote:
> On 2015-08-25 13:34, Brian Norris wrote:
> > One more thing...
> > 
> > On Mon, Aug 03, 2015 at 11:27:26AM +0200, Stefan Agner wrote:
> >> --- /dev/null
> >> +++ b/drivers/mtd/nand/vf610_nfc.c
> >> @@ -0,0 +1,645 @@
> > ...
> >> +struct vf610_nfc {
> >> +	struct mtd_info mtd;
> >> +	struct nand_chip chip;
> >> +	struct device *dev;
> >> +	void __iomem *regs;
> >> +	struct completion cmd_done;
> >> +	uint buf_offset;
> >> +	int page_sz;
> > 
> > AFAICT (even with the 2nd patch), you never really use this field. You
> > just set it/increment it, but don't use it for anything. Kill it?
> 
> It is used in the write path, I think I meant to use it for subpage
> writes, when I thought it would just mean to transfer only parts of the
> page to the controller.

Ah, you're right. Sorry, I missed that. I got mixed up seeing most of
your uses of 'page_sz' were for a local variable of the same name, not
this field.

> However, as the subpage discussion basically concluded in not using it
> for now on this controller, we can as well transfer the complete page
> (page_sz). Or is there another case in which vf610_nfc_write_buf could
> be called with less than page_sz?

I'll leave that up to you. I'm perfectly fine leaving it in, now that I
see its proper use. Just in case things change in the future, I think it
does help to clarify the flow of information a little. Although, I might
recommend a change in naming, since it could get confused with the
actual page size -- which is normally constant -- whereas this field
changes dynamically depending on the command-in-flight.

Perhaps the struct could have 'write_len' (to help represent an action)
and the local variable in vf610_nfc_command() could be 'tfr_len' (to
distinguish how it isn't necessarily identical to 'write_len')? Just
throwing (likely bad) ideas out there.

Regards,
Brian
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