linux-kernel - Re: [PATCH] Documentation: dt: mtd: replace "nor-jedec" binding with "jedec,spi-nor"

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Date:	Thu, 21 May 2015 10:39:34 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Rafał Miłecki <zajec5@...il.com>
Cc:	Brian Norris <computersforpeace@...il.com>,
	"linux-mtd@...ts.infradead.org" <linux-mtd@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Marek Vasut <marex@...x.de>,
	linux-spi <linux-spi@...r.kernel.org>
Subject: Re: [PATCH] Documentation: dt: mtd: replace "nor-jedec" binding with "jedec,spi-nor"

Hi Rafal, Brian,

On Thu, May 21, 2015 at 10:25 AM, Rafał Miłecki <zajec5@...il.com> wrote:
> On 21 May 2015 at 10:15, Brian Norris <computersforpeace@...il.com> wrote:
>> On Thu, May 21, 2015 at 10:01:05AM +0200, Rafał Miłecki wrote:
>>> On 21 May 2015 at 09:25, Brian Norris <computersforpeace@...il.com> wrote:
>>> >> > For platform devices, you might as well just use the name of the driver,
>>> >> > which is 'm25p80'. Isn't that how most platform devices are matched with
>>> >> > drivers?
>>> >>
>>> >> Yes and I think it's ugly because it keeps causing the warning about
>>> >> read flash model not matching specified one (m25p80).
>>> >
>>> > Sure, I agree.
>>> >
>>> >> Are you
>>> >> seriously not going to allow platform stuff *clearly* request flash
>>> >> model detection (JEDEC RDID OP)? Just because they don't use DT?
>>> >
>>> > No, this isn't about "allowing" anything. It's just that my primary
>>> > concern was to get the DT binding straightened out properly. Linus'
>>> > current tree now has the proper binding, but the m25p80.c code doesn't
>>> > quite bind properly. It will work if "jedec,spi-nor" is the first
>>> > entry in the compatible property (and so it becomes the 'modalias', but
>>> > not second, third, etc. So my patch fixes that properly.
>>> >
>>> > Now, the secondary concern is that you want platform devices to specify
>>> > something generic, and that doesn't yield a "found X, expected Y"
>>> > message. I'm perfectly fine with fixing that too, if you have a patch
>>> > for it. What do you propose?
>>>
>>> Maybe I wasn't clear enough. I was going to start using struct
>>> flash_platform_data with
>>> .type = "spi-nor",
>>> but your proposed patch removes support for such name.
>>
>> Ah, OK. So that's the part I was overlooking.
>>
>>> While I like matching DT *clearly* against the whole "jedec,spi-nor"
>>> string (really, I'm all for it), I'm confused what I should use for
>>> platform stuff now. I don't have any proposal as my initial plan was
>>> exactly to use this "spi-nor".
>>> I guess I don't want to re-add support for "spi-nor" (as you just
>>> proposed to remove it),
>>
>> I wasn't really trying to remove "spi-nor", that was mostly a side
>> effect.
>
> OK, I think we understand each other now :)
>
>>> so I think I have to bounce the question: what
>>> alternative do you propose?
>>
>> I think your comments suggest that I shouldn't be removing "spi-nor"
>> from m25p_ids[] nor from this block:
>>
>>         if (data && data->type)
>>                 flash_name = data->type;
>>         else if (!strcmp(spi->modalias, "spi-nor"))
>>                 flash_name = NULL; /* auto-detect */
>>         else
>>                 flash_name = spi->modalias;
>>
>> So it stays in both m25p_ids[] and .of_match_table.
>>
>> I suppose that can work. It then allows people to do weird stuff like:
>>
>>         compatible = "idontknowwhatimdoing,spi-nor";
>>
>> in their device tree. But other than that, there's not much downside I don't
>> think.
>
> It sounds like a reasonable solution. I guess there isn't a perfect
> one. Even if we decide to go for sth like "jedec-spi-nor", there
> always will be a chance of someone using
> compatible = "idontknowwhatimdoing,jedec-spi-nor";
> So if you rework your patch to leave "spi-nor" support in m25p_ids and
> conditions block, it should be OK.

Typically platform devices just use the driver's name. Hence IMHO there's
no need to add a shiny new spi-nor device name.

So what's wrong with using "m25p80", and treating that as auto-detect iff
!spi->dev.of_node?
Non-autodetect platform_devices use flash_platform_data.type anyway,
and thus fall under the first "if" clause above, don't they?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds
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