linux-kernel - Re: [PATCH v3 2/4] kstrtox: introduce a safer version of memparse()

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Message-ID: <bd4f25a9-9584-42bc-bde8-b9ca82cbc1c5@infradead.org>
Date: Wed, 3 Jan 2024 22:50:55 -0800
From: Randy Dunlap <rdunlap@...radead.org>
To: Qu Wenruo <quwenruo.btrfs@....com>, Qu Wenruo <wqu@...e.com>,
 linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
 akpm@...ux-foundation.org, christophe.jaillet@...adoo.fr,
 andriy.shevchenko@...ux.intel.com, David.Laight@...LAB.COM, ddiss@...e.de,
 geert@...ux-m68k.org
Subject: Re: [PATCH v3 2/4] kstrtox: introduce a safer version of memparse()



On 1/3/24 22:42, Qu Wenruo wrote:
> 
> 
> On 2024/1/4 17:00, Randy Dunlap wrote:
>> Hi,
>>
> [...]
>>> + *        parameter.
>>> + *
>>> + * @suffixes:    The suffixes which should be parsed. Use logical ORed
>>> + *        memparse_suffix enum to indicate the supported suffixes.
>>> + *        The suffixes are case-insensive, all 2 ^ 10 based.
>>
>>                          case-insensitive
>>
>>> + *        Supported ones are "KMGPTE".
>>> + *        NOTE: If one suffix out of the supported one is hit, it would
>>
>>                                                  ones
>>
>>> + *        end the parse normally, with @retptr pointed to the unsupported
>>> + *        suffix.
>>
>> Could you explain (or give an example) of "to the unsupported suffix"?
>> This isn't clear IMO.
> 
> Oh, my bad, that sentence itself is not correct.
> 
> What I really want to say is:
> 
>  If one suffix (one of "KMGPTE") is hit but that suffix is not
>  specified in the @suffxies parameter, it would end the parse normally,
>  with @retptr pointed to the (unsupported) suffix.

(corrected ^^^)

> The example would be the "68k " case in the ok cases in the next patch.
> We have two different cases for the same "68k" string, with different
> @suffixes and different results:
> 
>     "68k ", KMGPTE -> 68 * 1024, @retptr at " ".
>     "68k ", M -> 68, @retptr at 'k'.
> 
> I don't have a better expression here unfortunately, maybe the special
> case is not even worthy explaining?
> 

No, the corrected paragraph above is good. (s/would end/ends/)

Except for one thing: the examples here terminate on a space character,
but the function kernel-doc says "null-terminated":

+/**
+ * memparse_safe - convert a string to an unsigned long long, safer version of
+ * memparse()
+ *
+ * @s:		The start of the string. Must be null-terminated.




>>
>>> + *
>>> + * @res:    Where to write the result.
>>> + *
>>> + * @retptr:    (output) Optional pointer to the next char after parse completes.
>>> + *
>>> + * Return 0 if any valid numberic string can be parsed, and @retptr updated.
>>> + * Return -INVALID if no valid number string can be found.
>>> + * Return -ERANGE if the number overflows.
>>> + * For minus return values, @retptr would not be updated.
>>
>>   * Returns:
>>   * * %0 if any valid numeric string can be parsed, and @retptr is updated.
>>   * * %-EINVAL if no valid number string can be found.
>>   * * %-ERANGE if the number overflows.
>>   * * For negative return values, @retptr is not updated.
>>
>>
>> For *ALL* of the comments, I request/suggest that you change the "would be" or
>> "would not be" to "is" or "is not" or whatever present tense words make the
>> most sense.
> 
> No problem.


-- 
#Randy