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

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

[Max Nikulin]

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

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

[Bagas Sanjaya]

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On Sat, Nov 29, 2025 at 12:12:32AM +0700, Max Nikulin wrote:
> +Usage of ``/dev/scd?`` as alternate SCSI CD-ROM names for ``sr?`` devices
> +ended around year 2011.

What about "Support for /dev/scd? as alternative names for /dev/sr? has been
removed in 2011"?

Thanks. 

-- 
An old man doll... just what I always wanted! - Clara

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

[Max Nikulin]

On 29/11/2025 13:13, Bagas Sanjaya wrote:
> On Sat, Nov 29, 2025 at 12:12:32AM +0700, Max Nikulin wrote:
>> +Usage of ``/dev/scd?`` as alternate SCSI CD-ROM names for ``sr?`` devices
>> +ended around year 2011.
> 
> What about "Support for /dev/scd? as alternative names for /dev/sr? has been
> removed in 2011"?

If others support your suggestion then I do not mind. Feel free to 
commit preferred variant ignoring my patch.

I would be more verbose however by adding that it was removed namely 
from udev:

Creation of ``/dev/scd?`` alternative names for ``sr?`` CD-ROM and other 
optical drives (using SCSI commands) was removed in ``udev-174`` 
(released in 2011).

Perhaps I am biased by my confusion. Noticed that wodim tries to access 
currently absent /dev/scd0 for kernels >= X.6, I tried git blame game in 
kernel repository to find kernel version when scd<N> were renamed to 
sr<N>. It took some time for me to realize that it is impossible to 
determine scd vs. sr from kernel version. That is why I would consider 
adding explicit mention of udev. Otherwise for me it sounds like that 
scd? names were removed from kernel. I am not a native English speaker, 
so I do not insist on my variant.

How long I should wait for comments before submitting another revision 
of the patch? I hope, pending changes are not an obstacle for those who 
are tempting to review the whole devices.rst file.

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

[Bagas Sanjaya]

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On Sat, Nov 29, 2025 at 10:01:41PM +0700, Max Nikulin wrote:
> On 29/11/2025 13:13, Bagas Sanjaya wrote:
> > On Sat, Nov 29, 2025 at 12:12:32AM +0700, Max Nikulin wrote:
> > > +Usage of ``/dev/scd?`` as alternate SCSI CD-ROM names for ``sr?`` devices
> > > +ended around year 2011.
> > 
> > What about "Support for /dev/scd? as alternative names for /dev/sr? has been
> > removed in 2011"?
> 
> If others support your suggestion then I do not mind. Feel free to commit
> preferred variant ignoring my patch.
> 
> I would be more verbose however by adding that it was removed namely from
> udev:
> 
> Creation of ``/dev/scd?`` alternative names for ``sr?`` CD-ROM and other
> optical drives (using SCSI commands) was removed in ``udev-174`` (released
> in 2011).

This one looks better.

> 
> Perhaps I am biased by my confusion. Noticed that wodim tries to access
> currently absent /dev/scd0 for kernels >= X.6, I tried git blame game in
> kernel repository to find kernel version when scd<N> were renamed to sr<N>.
> It took some time for me to realize that it is impossible to determine scd
> vs. sr from kernel version. That is why I would consider adding explicit
> mention of udev. Otherwise for me it sounds like that scd? names were
> removed from kernel. I am not a native English speaker, so I do not insist
> on my variant.
> 
> How long I should wait for comments before submitting another revision of
> the patch? I hope, pending changes are not an obstacle for those who are
> tempting to review the whole devices.rst file.

Since we're in rc7 (and 6.18 release is tomorrow), you need to wait until at
least two weeks later (when 6.19 merge window closes) and repost. Don't forget
to Cc me anyway.

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

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