[PATCH] docs: admin: devices: /dev/sr<N> for SCSI CD-ROM

[Max Nikulin <manikulin@gmail.com>]

Don't claim that /dev/sr<N> device names for SCSI CD-ROM drives are
deprecated and don't recommend /dev/scd<N> alternate names for them.

/dev/scd<N> device names for SCSI CD-ROM drives are not in use for more
than a decade, see commit [1] that was a part of udev release 174.
Earlier related rules were volatile, sometimes /dev/scd<N> were syminks
to /dev/sr<N>, sometimes vice versa.

Recognizing of root=/dev/scd<N> kernel command line argument was removed
in kernel 2.5.45 [2].

In the docs /dev/scd<N> are recommended names since 2.6.9 [3].
Mention of these names appeared much earlier in 1.3.22 [4].

[1] https://git.kernel.org/pub/scm/linux/hotplug/udev.git/commit/?id=d132be4d58
    2011-08-12 14:05:19 +0200 Kay Sievers.
    rules: remove legacy rules for cdrom and usb printer

[2] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/init?h=v2.5.45&id=51924607bd
    2002-10-29 00:47:58 -0800 Alexander Viro.
    [PATCH] removal of root_dev_names[]

[3] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/diff/Documentation/devices.txt?h=v2.6.9-rc4&id=a74e11ffeda
    2004-03-16 15:09:38 -0800 Andrew Morton:
    [PATCH] devices.txt: typos and removal of dead devices

[4] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/tree/Documentation/devices.txt?h=v2.6.9-rc4&id=8f0ec1f9369
    Linus Torvalds: Import 1.3.22

Signed-off-by: Max Nikulin <manikulin@gmail.com>

---

I hope, the suggested changes make kernel docs more close to reality.

During discussion of a bug in wodim (a fork of cdrecord) I was confused
that docs recommend /dev/scd<N> as SCSI CD-ROM name. The following
thread did not clarify the issue:

https://lore.kernel.org/lkml/20061105100926.GA2883@pelagius.h-e-r-e-s-y.com/
Scsi cdrom naming confusion; sr or scd? Sun, 5 Nov 2006 10:09:26 +0000

If I'm not mistaken, "sr" was always used internally in the driver
"scd" were limited to log strings. I have added SCSI subsystem to CC
to confirm that there is no objection from their side.

It seems, de-facto /dev/sr<N> names are used and I think, /dev/scd<N>
should be avoided. I may be completely wrong though.

I wouldn't mind if you discard this patch and to commit another one
with better wording instead.
---
 Documentation/admin-guide/devices.rst | 4 +++-
 Documentation/admin-guide/devices.txt | 6 +++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/devices.rst b/Documentation/admin-guide/devices.rst
index e3776d77374b..515338d0e406 100644
--- a/Documentation/admin-guide/devices.rst
+++ b/Documentation/admin-guide/devices.rst
@@ -97,9 +97,11 @@ It is recommended that these links exist on all systems:
 /dev/bttv0	video0		symbolic	Backward compatibility
 /dev/radio	radio0		symbolic	Backward compatibility
 /dev/i2o*	/dev/i2o/*	symbolic	Backward compatibility
-/dev/scd?	sr?		hard		Alternate SCSI CD-ROM name
 =============== =============== =============== ===============================
 
+Usage of ``/dev/scd?`` as alternate SCSI CD-ROM names for ``sr?`` devices
+ended around year 2011.
+
 Locally defined links
 +++++++++++++++++++++
 
diff --git a/Documentation/admin-guide/devices.txt b/Documentation/admin-guide/devices.txt
index 94c98be1329a..c480f230aa4a 100644
--- a/Documentation/admin-guide/devices.txt
+++ b/Documentation/admin-guide/devices.txt
@@ -389,11 +389,11 @@
 		    ...
 
   11 block	SCSI CD-ROM devices
-		  0 = /dev/scd0		First SCSI CD-ROM
-		  1 = /dev/scd1		Second SCSI CD-ROM
+		  0 = /dev/sr0		First SCSI CD-ROM
+		  1 = /dev/sr1		Second SCSI CD-ROM
 		    ...
 
-		The prefix /dev/sr (instead of /dev/scd) has been deprecated.
+		In the past the prefix /dev/scd (instead of /dev/sr) was used and even recommended.
 
   12 char	QIC-02 tape
 		  2 = /dev/ntpqic11	QIC-11, no rewind-on-close
-- 
2.39.5