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Date: Mon, 7 Aug 2017 22:34:03 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Prarit Bhargava <prarit@redhat.com>
Cc: Mark Salyzyn <salyzyn@android.com>, linux-kernel@vger.kernel.org,
        Jonathan Corbet <corbet@lwn.net>, Petr Mladek <pmladek@suse.com>,
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        Olof Johansson <olof@lixom.net>, Josh Poimboeuf <jpoimboe@redhat.com>,
        linux-doc@vger.kernel.org
Subject: Re: [PATCH v3] printk: Add boottime and real timestamps
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On (08/07/17 08:41), Prarit Bhargava wrote:
[..]
> >> +static int printk_time_set(const char *val, const struct kernel_param *kp)
> >> +{
> >> +    char *param = strstrip((char *)val);
> >> +    int _printk_time;
> >> +
> >> +    if (strlen(param) != 1)
> >> +        return -EINVAL;
> > (see below) strlen is so restrictive, wouldn't it be nice(tm) to allow "boot",
> > "monotonic" or "realtime" strings? Certainly KISS can handle the first letters
> > for next to zero cost. (switch statement optimization)
> 
> Thanks Mark,
> 
> I had asked this question before and didn't get an answer: Do I need to
> worry about the ABI of /sys/modules/printk/parameters/time.  Since it hasn't
> been explicitly added to the stable ABI files, I'm going to assume it wasn't
> important enough to add it.  Looking at google, however, leads to a lot
> of hits for 'printk.time' kernel parameters settings so I think I better
> maintain the legacy boolean settings.

yes, please. we have to preserve it.

> I'm going to do: 0/n/N/1/y/Y to maintain the existing ABI, and add (as you
> suggest above 'disable|local|boottime|monotonic|realtime' as valid
> parameters.
> 
> >> +
> >> +    switch (param[0]) {
> >> +    case '0':
> >> +    case 'n':
> >> +    case 'N':
> > I would wish for a few more 'convenience' cases:
> > 
> > case 'd': case 'D': /* Disable */
> 
> It would be trivial then to add only the lower case options (I dislike upper
> case settings ...) by adding

yes, please. lower case only.

	-ss