linux-kernel - Re: [PATCH v4 03/11] mtd: spi-nor: core: Use auto-detection only once

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Message-ID: <6f81d38b-5e4b-eaf7-0466-3c6fe5e84996@microchip.com>
Date:   Thu, 21 Apr 2022 13:41:57 +0000
From:   <Tudor.Ambarus@...rochip.com>
To:     <p.yadav@...com>
CC:     <michael@...le.cc>, <miquel.raynal@...tlin.com>, <richard@....at>,
        <vigneshr@...com>, <linux-mtd@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <Takahiro.Kuwano@...ineon.com>
Subject: Re: [PATCH v4 03/11] mtd: spi-nor: core: Use auto-detection only once

On 4/21/22 16:16, Pratyush Yadav wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On 21/04/22 07:18AM, Tudor.Ambarus@...rochip.com wrote:
>> Hi, Pratyush,
>>
>> I forgot to remove few checks, would you please remove them when applying?
>> See below.
>>
>> On 4/20/22 13:34, 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@...rochip.com>
>>> Reviewed-by: Michael Walle <michael@...le.cc>
>>> ---
>>>  drivers/mtd/spi-nor/core.c | 13 ++++++++-----
>>>  1 file changed, 8 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/mtd/spi-nor/core.c b/drivers/mtd/spi-nor/core.c
>>> index b9cc8bbf1f62..b55d922d46dd 100644
>>> --- a/drivers/mtd/spi-nor/core.c
>>> +++ b/drivers/mtd/spi-nor/core.c
>>> @@ -2896,13 +2896,14 @@ static const struct flash_info *spi_nor_get_flash_info(struct spi_nor *nor,
>>>  {
>>>     const struct flash_info *info = NULL;
>>>
>>> -   if (name)
>>> +   if (name) {
>>>             info = spi_nor_match_name(nor, name);
>>> +           if (IS_ERR(info))
>>> +                   return info;
>>
>> As Michael suggested spi_nor_match_name() returns NULL or valid entry, so this
>> check is not necessary, let's remove them.
>>
>>> +   }
>>>     /* Try to auto-detect if chip name wasn't specified or not found */
>>>     if (!info)
>>> -           info = spi_nor_read_id(nor);
>>> -   if (IS_ERR_OR_NULL(info))
>>> -           return ERR_PTR(-ENOENT);
>>> +           return spi_nor_read_id(nor);
>>>
>>>     /*
>>>      * If caller has specified name of flash model that can normally be
>>> @@ -2994,7 +2995,9 @@ int spi_nor_scan(struct spi_nor *nor, const char *name,
>>>             return -ENOMEM;
>>>
>>>     info = spi_nor_get_flash_info(nor, name);
>>> -   if (IS_ERR(info))
>>> +   if (!info)
>>> +           return -ENOENT;
>>
>> also according to Michael, this change is not needed as spi_nor_get_flash_info() can't
>> return NULL. Here we can keep the code as it was. Let me know if you want me to respin.
> 
> TBH I don't think a NULL check here hurts much since the behaviour might
> change later, and error paths don't get exercised as often. But I have

I agree, but at the same time we're introducing checks gratuitously. Since
Michael cared about it, it's fine that we removed it. I don't care too much
about it.

> made both changes when applying. You can double-check at [0] if you
> want.> 
> [0] https://github.com/prati0100/linux-0day/commit/67d913746833ee54bf4c661040f3ef13657dffd8

looks good.

btw: I think this patch
https://github.com/prati0100/linux-0day/commit/b45bbff85d49529f8daff83c341a292f6c6492ca
may introduce a regression on some atmel chips. Let me try it please.
> 
>>
>>> +   else if (IS_ERR(info))
>>>             return PTR_ERR(info);
>>>
>>>     nor->info = info;
>>
> 
> --
> Regards,
> Pratyush Yadav
> Texas Instruments Inc.