linux-kernel - Re: [PATCH 1/1 v2] driver:mtd:spi-nor: Add Micron quad I/O support

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Date:	Mon, 29 Sep 2014 20:57:31 +0200
From:	Marek Vasut <marex@...x.de>
To:	bpqw <bpqw@...ron.com>
Cc:	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	Brian Norris <computersforpeace@...il.com>,
	"shijie8@...il.com" <shijie8@...il.com>,
	"geert+renesas@...der.be" <geert+renesas@...der.be>,
	"grmoore@...era.com" <grmoore@...era.com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1 v2] driver:mtd:spi-nor: Add Micron quad I/O support

On Monday, September 29, 2014 at 02:30:04 AM, bpqw wrote:
> >> For Micron spi norflash,you can enable Quad spi transfer by clear
> >> EVCR(Enhanced Volatile Configuration Register) Quad I/O protocol bit.
> >
> >OK, this information is nice and all, but what does this patch do? I can't
> >learn this information from the commit message as it is, can I ? And ,
> >the purpose of the commit message is exactly to summarize the change the
> >patch implements.
> 
> you don't understand what purpose of this patch!

Well, I dare to say, reacting to feedback like you just did won't make you many 
allies around here.

> just as subject and commit
> message described, it is for enable Micron Quad spi transfer mode.

I understand the subject part. The commit message, on the other hand, just 
states that it is possible to frob with a certain register to achieve a certain 
effect ; the commit message does not state what this patch does or how is the 
patch useful.

Does this patch enable the bit or does it disable the bit ? I cannot tell 
without looking into the code , I really have no clue just by reading the 
subject and the commit message.

> do you
> read the spi-nor.c file?

No, I didn't even look at the code.

> please pay attention to the set_quad_mode()
> function.

No, what set_quad_mode_function() are you talking about ...

> by the way,I can add more commit message for it,but I think it is
> redundant,don't need.

The commit message shall state what the patch does in the first place, what the 
hardware can do is ortogonal to that. The commit message can be as short as:

The hardware supports 4-bit I/O when bit FOO is set in register BAR. This patch 
adds function that sets bit FOO in register BAR to enable 4-bit I/O if condition 
BAZ and QUUX are met.

Then I do not even have to look at the code if I want to just get the high-level 
overview of what the patch does. If I want to know the details, I will look into 
the code.

Do you know what I'm getting at ?

[...]

Best regards,
Marek Vasut
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