linux-kernel - Re: [PATCH v1 1/8] lib/string: introduce match

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Message-ID: <1452524400.26146.32.camel@linux.intel.com>
Date:	Mon, 11 Jan 2016 17:00:00 +0200
From:	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Tejun Heo <tj@...nel.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Dmitry Eremin-Solenikov <dbaryshkov@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	David Airlie <airlied@...ux.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Subject: Re: [PATCH v1 1/8] lib/string: introduce match_string() helper

On Sat, 2016-01-09 at 13:57 +0200, Andy Shevchenko wrote:
> On Sat, Jan 9, 2016 at 3:12 AM, Sergey Senozhatsky
> <sergey.senozhatsky@...il.com> wrote:
> > Andy Shevchenko wrote:
> > [..]
> > > > 
> > > > strncmp() case seems to be quite common.
> > > 
> > > Like I answered to Rasmus, please, provide real examples.
> > 
> > [..]
> > > > int nmatch_string(array, array_size, string, string_len)
> > > > {
> > > >       do {
> > > >               strncmp();
> > > >       } while ();
> > > > }
> > > > 
> > > > int match_string(array, array_size, string)
> > > > {
> > > >       return nmatch_string(array, array_size, string,
> > > > strlen(string));
> > > > }
> > > 
> > > See above.
> > 
> > after some quick and inaccurate grepping, well, probably you're
> > right - not worth it.
> 
> Good grep anyway, it clearly shows that there is hard to generalize
> which limit to use: a) length of a first argument / item from a list,
> b) length of a second argument or a constant.
> 
> > arch/mips/bcm63xx/boards/board_bcm963xx.c  void __init
> > board_prom_init(void)
> > net/irda/irnet/irnet_irda.c   irnet_dname_to_daddr()
> > arch/powerpc/sysdev/ppc4xx_cpm.c static ssize_t cpm_idle_store()
> > arch/x86/ras/mce_amd_inj.c static int __set_inj
> > drivers/hwtracing/intel_th/msu.c mode_store
> > drivers/pci/pcie/aer/ecrc.c void pcie_ecrc_get_policy
> > drivers/pci/pcie/aspm.c pcie_aspm_set_policy
> > drivers/scsi/aic7xxx/aic7xxx_osm.c aic7xxx_setup
> > drivers/scsi/aic7xxx/aic79xx_osm.c aic79xx_setup
> > drivers/scsi/scsi_transport_fc.c static int get_fc_##title##_match
> > drivers/staging/android/ion/hisilicon/hi6220_ion.c get_type_by_name
> > drivers/staging/lustre/lustre/lmv/lproc_lmv.c placement_name2policy
> > drivers/xen/sys-hypervisor.c pmu_mode_store

Thought more about those cases.

If you would like you may introduce something like

int nmatch_string(array, array_size, string, int len)
{
  if (len < 0)
    return match_string();

  for (…) {
    size_t itemlen = (len > 0) ? len : strlen(array[index]);
…
    if (!strncmp(array[index], string, itemlen))
      return index;
  }
  return -EINVAL;
}

And convert existing users where it makes sense.

-- 
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Intel Finland Oy