linux-kernel - Re: [RFC PATCH v1 6/6] mtd: spi-nor: introduce support for displaying deprecation message

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Message-Id: <D0MHEH8OOS44.2PPBZ3LFU4QG3@kernel.org>
Date: Wed, 17 Apr 2024 16:52:42 +0200
From: "Michael Walle" <mwalle@...nel.org>
To: "Pratyush Yadav" <pratyush@...nel.org>
Cc: "Tudor Ambarus" <tudor.ambarus@...aro.org>, "Miquel Raynal"
 <miquel.raynal@...tlin.com>, "Richard Weinberger" <richard@....at>,
 "Vignesh Raghavendra" <vigneshr@...com>, <linux-kernel@...r.kernel.org>,
 <linux-mtd@...ts.infradead.org>
Subject: Re: [RFC PATCH v1 6/6] mtd: spi-nor: introduce support for
 displaying deprecation message

Hi,

On Wed Apr 17, 2024 at 4:36 PM CEST, Pratyush Yadav wrote:
> On Fri, Apr 12 2024, Michael Walle wrote:
>
> > SPI-NOR will automatically detect the attached flash device most of the
> > time. We cannot easily find out if boards are using a given flash.
> > Therefore, introduce a (temporary) flag to display a message on boot if
>
> Why temporary? There will always be a need to deprecate one flash or
> another. Might as well keep the flag around.

Mh, yes I agree. That also means that this flag will not have any
users (most) of the time (hopefully ;) ).

> Also, this patch/series does not add any users of the deprecated flag.
> If you have some flashes in mind, it would be good to add them to the
> patch/series.

This is just an RFC to see if whether you Tudor agree with me :) But
I was about to add it to the evervision/cypress FRAMs.

> I like the idea in general. Do you think we should also print a rough
> date for the deprecation as well?

Might make sense, any suggestions?

> > support for a given flash device is scheduled to be removed in the
> > future.
> >
> > Signed-off-by: Michael Walle <mwalle@...nel.org>
> > ---
> >  drivers/mtd/spi-nor/core.c | 12 ++++++++++++
> >  drivers/mtd/spi-nor/core.h |  1 +
> >  2 files changed, 13 insertions(+)
> >
> > diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> > index 58d310427d35..a294eef2e34a 100644
> > --- a/drivers/mtd/spi-nor/core.c
> > +++ b/drivers/mtd/spi-nor/core.c
> > @@ -3312,6 +3312,7 @@ static const struct flash_info *spi_nor_get_flash_info(struct spi_nor *nor,
> >  						       const char *name)
> >  {
> >  	const struct flash_info *jinfo = NULL, *info = NULL;
> > +	const char *deprecated = NULL;
> >  
> >  	if (name)
> >  		info = spi_nor_match_name(nor, name);
> > @@ -3326,6 +3327,17 @@ static const struct flash_info *spi_nor_get_flash_info(struct spi_nor *nor,
> >  			return jinfo;
> >  	}
> >  
> > +	if (info && (info->flags & SPI_NOR_DEPRECATED))
> > +		deprecated = info->name;
> > +	else if (jinfo && (jinfo->flags & SPI_NOR_DEPRECATED))
> > +		deprecated = jinfo->name;
> > +
> > +	if (deprecated)
> > +		pr_warn("Your board or device tree is using a SPI NOR flash (%s) with\n"
> > +			"deprecated driver support. It will be removed in future kernel\n"
>
> Nit: "removed in a future kernel version"
>
> > +			"version. If you feel this shouldn't be the case, please contact\n"
> > +			"us at linux-mtd@...ts.infradead.org\n", deprecated);
> > +
>
> Hmm, this isn't so nice. I'd suggest doing something like:
>
> 	/*
>          * If caller has specified name of flash model that can normally be
>          * ...
>          */
> 	info = jinfo ?: info;
>
> 	if (info->flags & SPI_NOR_DEPRECATED)
>         	pr_warn(...);

Actually, I had that, *but* I was thinking we might only check the
detected flash and not the one specified in the device tree. But
thinking about that again, I guess it makes sense because:
 - that's the actually used flash driver
 - having jinfo != info will print that other warning, thus this
   case is hopefully very unlikely.

>
> 	return info;
>
> >  	/*
> >  	 * If caller has specified name of flash model that can normally be
> >  	 * detected using JEDEC, let's verify it.
> > diff --git a/drivers/mtd/spi-nor/core.h b/drivers/mtd/spi-nor/core.h
> > index 8552e31b1b07..0317d8e253f4 100644
> > --- a/drivers/mtd/spi-nor/core.h
> > +++ b/drivers/mtd/spi-nor/core.h
> > @@ -524,6 +524,7 @@ struct flash_info {
> >  #define SPI_NOR_NO_ERASE		BIT(6)
> >  #define SPI_NOR_QUAD_PP			BIT(8)
> >  #define SPI_NOR_RWW			BIT(9)
> > +#define SPI_NOR_DEPRECATED		BIT(15)
>
> If you do agree with my suggestion of making it permanent, would it make
> more sense to make it BIT(10) instead. Or BIT(9) once you move up the
> others because we no longer have BIT(7).

Or just BIT(7) and avoid any code churn :)

-michael

>
> >  
> >  	u8 no_sfdp_flags;
> >  #define SPI_NOR_SKIP_SFDP		BIT(0)


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