Messages in this thread | | | Subject | Re: [PATCH 1/5] vsprintf/Documentation: Add X to %*ph extension to output upper case hex | From | Joe Perches <> | Date | Fri, 27 Aug 2021 19:49:24 -0700 |
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On Fri, 2021-08-27 at 11:49 +0300, Andy Shevchenko wrote: > On Fri, Aug 27, 2021 at 01:08:10AM -0700, Joe Perches wrote: > > On Fri, 2021-08-27 at 10:48 +0300, Andy Shevchenko wrote: > > > On Thu, Aug 26, 2021 at 11:43:01AM -0700, Joe Perches wrote: > > > > A few sysfs output uses of hex arrays are uppercase and are nominally ABI. > > > > > > > > Add a mechanism to the existing vsprintf %*ph hex output extension to > > > > support upper case hex output. > > > > > > ... > > > > > > > + The preferred output is lowercase > > > > %*ph 00 01 02 ... 3f > > > > %*phC 00:01:02: ... :3f > > > > %*phD 00-01-02- ... -3f > > > > %*phN 000102 ... 3f > > > > + Formats with X are uppercase, used for backwards compatibility > > > > + %*phX 00 01 02 ... 3F > > > > + %*phCX 00:01:02: ... :3F > > > > + %*phDX 00-01-02- ... -3F > > > > + %*phNX 000102 ... 3F > > > > > > Why not using %*pH...? > > > > I find X more intelligible. > > > > > > + char locase = 0x20; /* ASCII OR'd for lower case see: number() */ > > > > > > If you use h vs H, you may derive this from (fmt[...] & SMALL). > > > > It's not necessary to use any more of the rather limited vsprintf > > extension namespace. > > I understand your concern, but %*ph is quite widely used (I guess top 1 or 2 > among all %p extensions),
Cumulatively 3rd after %pM and %pOF
> its performance degradation with your code may affect > a lot of other users and hence a kernel as a whole. > > So, that's why my proposal stays.
Knock yourself out.
> Of course you may provide a benchmark (btw, where are the test cases for this?)
You are welcome to provide both test cases and benchmarks. I find the whole thing rather dull.
> for yours and mine variant and we will see if it makes sense to optimize.
It doesn't. Anyone thinking there is a required printf/vsprintf optimization in the kernel is decidedly barking up the wrong tree.
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