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SubjectRe: [PATCH v2 3/8] mtd: spi-nor: core: Use auto-detection only once
On 21/03/22 11:38PM, Michael Walle wrote:
> Am 2022-03-21 18:42, schrieb Pratyush Yadav:
> > 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;
> > > > }
>
> +1 for the flow. But is it correct that we just ignore any former
> error and just replace it with ENOENT? Should we return NULL here
> and let the caller handle the translation from NULL to ENOENT (and
> keeping any other errors)
>
> > >
> > > 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.
>
> But what does it cost to just add the error check now so it won't
> be forgotten in the future?
>
> if (name) {
> info = spi_nor_match_name();
> if (IS_ERR(info))
> return info;
> }
> if (!info)
> return spi_nor_read_id();
>
> <flash model check code follows here>
>
> And then let the caller handle NULL and translate it to ENOENT.

Sounds good to me.

--
Regards,
Pratyush Yadav
Texas Instruments Inc.

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