From: danielfsantos@att.net
To: linux-kbuild <linux-kbuild@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, Michal Marek <mmarek@suse.cz>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
        David Howells <dhowells@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Michael Kerrisk <mtk.manpages@gmail.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        George Spelvin <linux@horizon.com>
Subject: [PATCH 0/5] Preliminary: Add error names & descrptions to printks
Date: Tue, 17 Sep 2013 18:08:32 -0500
Message-Id: <1379459317-13046-1-git-send-email-daniel.santos@pobox.com>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1626
Lines: 37


This is a preliminary patch set as the root Makefile changes are not yet
correct.

Summary

Typically, we don't care about error messages or names in the kernel because
userspace will manage that.  But sometimes we need to output an error number
to printks and that creates a situation where a user, system admistrator or
developer must find an error number reference to figure out what went wrong
with a particular driver or whatever.  This patch adds two alternatives at
increasing memory costs:

1. print the number in addition to the name for 2k extra or
2. print the number, name and description for 6k extra.

This is fairly low cost for the person who wants to make life just a little
bit easier. The format of each is respectively the same as the following:

  printk("%d (%s)", err, err_name);
  printk("%d (%s: %s)", err, err_name, err_desc);

Theory

Error messages aren't printed often, so this data and code is designed to be
compact at the expense of speed.  Rather than using an array of strings that
would require both the text and a pointer to that text, we just cram a range
of error names or descriptions into a single string with null character
delimiters.  When we want to retrieve a string, we just iterate through that
string and count nulls.  This is slow, but it keeps it compact. (If this
becomes a bottleneck then something else is seriously wrong! :)

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