Re: [PATCH v2 3/8] mtd: spi-nor: core: Use auto-detection only once

From: Pratyush Yadav <p.yadav@ti.com>
To: <Tudor.Ambarus@microchip.com>
Cc: <michael@walle.cc>, <miquel.raynal@bootlin.com>, <richard@nod.at>,
	<vigneshr@ti.com>, <linux-mtd@lists.infradead.org>,
	<linux-kernel@vger.kernel.org>, <Nicolas.Ferre@microchip.com>
Subject: Re: [PATCH v2 3/8] mtd: spi-nor: core: Use auto-detection only once
Date: Mon, 21 Mar 2022 23:12:51 +0530	[thread overview]
Message-ID: <20220321174251.ehhobu26tgoxrbps@ti.com> (raw)
In-Reply-To: <b4e8c044-f16a-a72d-6047-c42cdcc253f1@microchip.com>

On 21/03/22 12:50PM, Tudor.Ambarus@microchip.com wrote:
> On 3/21/22 14:14, Pratyush Yadav wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > On 28/02/22 01:17PM, Tudor Ambarus wrote:
> >> In case spi_nor_match_name() returned NULL, the auto detection was
> >> issued twice. There's no reason to try to detect the same chip twice,
> >> do the auto detection only once.
> >>
> >> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> >> ---
> >>  drivers/mtd/spi-nor/core.c | 10 ++++++----
> >>  1 file changed, 6 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
> >> index f87cb7d3daab..b1d6fa65417d 100644
> >> --- a/drivers/mtd/spi-nor/core.c
> >> +++ b/drivers/mtd/spi-nor/core.c
> >> @@ -2894,13 +2894,15 @@ static const struct flash_info *spi_nor_match_name(struct spi_nor *nor,
> >>  static const struct flash_info *spi_nor_get_flash_info(struct spi_nor *nor,
> >>                                                      const char *name)
> >>  {
> >> -     const struct flash_info *info = NULL;
> >> +     const struct flash_info *info = NULL, *detected_info = NULL;
> >>
> >>       if (name)
> >>               info = spi_nor_match_name(nor, name);
> >>       /* Try to auto-detect if chip name wasn't specified or not found */
> >> -     if (!info)
> >> -             info = spi_nor_read_id(nor);
> >> +     if (!info) {
> >> +             detected_info = spi_nor_read_id(nor);
> >> +             info = detected_info;
> >> +     }
> >>       if (IS_ERR_OR_NULL(info))
> >>               return ERR_PTR(-ENOENT);
> >>
> >> @@ -2908,7 +2910,7 @@ static const struct flash_info *spi_nor_get_flash_info(struct spi_nor *nor,
> >>        * If caller has specified name of flash model that can normally be
> >>        * detected using JEDEC, let's verify it.
> >>        */
> >> -     if (name && info->id_len) {
> >> +     if (name && !detected_info && info->id_len) {
> >>               const struct flash_info *jinfo;
> >>
> >>               jinfo = spi_nor_read_id(nor);
> > 
> > I think the flow can be a little bit better. How about:
> > 
> >         if (name)
> >                 info = spi_nor_match_name();
> > 
> >         if (!info) {
> >                 info = spi_nor_read_id();
> >                 if (IS_ERR_OR_NULL(info))
> >                         return ERR_PTR(-ENOENT);
> > 
> >                 return info;
> >         }
> 
> Here we miss the IS_ERR check in case info is retrieved with spi_nor_match_name().
> Do you expect spi_nor_match_name() to ever return an error? As it is now it doesn't.
> I'm fine either way. In case you want me to follow your suggestion, give me a sign
> and I'll make a dedicated patch to move the IS_ERR_OR_NULL check. Will add your
> Suggested-by tag.

I think it should be safe to assume it won't ever return an error since 
all it does is iterate over an array that is always present. I don't see 
that changing in the foreseeable future either. So I think not having 
the IS_ERR check is fine.

-- 
Regards,
Pratyush Yadav
Texas Instruments Inc.

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