Some changes in write-cd-rules script

Some changes in write-cd-rules script

[Piter PUNK]

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Hi,

	I start to make udev-103 packages to test with slackware 11.0,
and i try to drop slackware's custom script to name CD and network
devices (my first work is against CD script) and begin to use the
provided in udev/extras/rule_generator.

	I got the following problems:

	1. In a machine with one CD-RW and one DVD drives, the current
	   script doesn't create the /dev/dvd symlink. It detects
	   the CD-RW and creates: cdrom, cdr and cdrw, and to the
	   DVD it creates: cdrom1 and dvd1.

	2. The rules created by the write-cd-rules needs to be
	   between udev.rules and cd-aliases-generator.rules. And in
	   slackware we doesn't ship many rules files, but only
	   one udev.rules.

	3. K3B uses /dev/writer, and write-cd-rules doesn't create
	   this link.

	To solve these problems i made some changes in write-cd-rules.
The changes are in attached patch and does:

	1. Always create numbered links, and made the without-number
	   link to the "first one" detect. In the CD-RW and DVD drive
	   it creates to the CD-RW: cdrom0, cdrom, cdr0, cdr, cdwriter,
	   and to DVD it creates: cdrom1, dvd1, dvd. And the users
	   can use /dev/dvd without problems.

	2. I added one test to check if there is one rule with the
	   same DEVPATH before create the links. If there is a rule
	   the script only returns 0 and exits. With that i can put
	   the cd-aliases-generator.rules inside udev.rules (i put
	   the cdrom_id.rules in udev.rules, too) and the things
	   still works. The ppl that use split files doesn't have
	   any impact with that.

	3. Create the /dev/writer to the most powerful writer:
	   DVD-RW/DVD-R/DVD-RAM -> CD-RW -> CD-R, in that order.

	I hope it can help. The 1 and 3 can be useful to everyone, and
the 2 is useful to ppl that ships only one big file.

					Thanks for all,

							Piter PUNK

PS> Sugestions and fixes are welcome -;)
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diff -Naur udev-103/extras/rule_generator/write_cd_rules udev-103pk/extras/rule_generator/write_cd_rules
--- udev-103/extras/rule_generator/write_cd_rules	2006-10-20 09:43:35.000000000 -0300
+++ udev-103pk/extras/rule_generator/write_cd_rules	2006-10-26 15:34:51.000000000 -0300
@@ -50,29 +50,60 @@
 	exit 1
 fi
 
-# Prevent concurrent processes from modifying the file at the same time.
-lock_rules_file
 
-# Check if the rules file is writeable.
-choose_rules_file
+if ! egrep "^ENV{ID_CDROM}==\"\?\*\", ENV{ID_PATH}==\"$ID_PATH\"" /etc/udev/rules.d/* &>/dev/null ; then 
+	# Prevent concurrent processes from modifying the file at the same time.
+	lock_rules_file
+
+	# Check if the rules file is writeable.
+	choose_rules_file
+
+	link_num=$(find_next_available 'cdrom[0-9]*')
+	[ "$link_num" = "" ] && link_num=0
+
+	match="ENV{ID_CDROM}==\"?*\", ENV{ID_PATH}==\"$ID_PATH\""
+
+	comment="$ID_MODEL ($ID_PATH)"
+
+		write_rule "$match" "cdrom$link_num" "$comment"
+		[ "x$(find_next_available 'cdrom')" = "x" ] && \
+			write_rule "$match" "cdrom"
+
+		if [ "$ID_CDROM_DVD" ]; then
+			write_rule "$match" "dvd$link_num"
+			[ "x$(find_next_available 'dvd')" = "x" ] && \
+				write_rule "$match" "dvd"
+			if [ "$ID_CDROM_DVD_R" -o "$ID_CDROM_DVD_RW" -o "$ID_CDROM_DVD_RAM" ]; then
+				write_rule "$match" "dvdrw$link_num"
+				[ "x$(find_next_available 'dvdwriter')" = "x" ] && \
+					write_rule "$match" "dvdwriter"
+				[ "x$(find_next_available 'writer')" = "x" ] && \
+					write_rule "$match" "writer"
+			fi
+		fi
+
+		if [ "$ID_CDROM_CD_R" ]; then
+			write_rule "$match" "cdr$link_num"
+			[ "x$(find_next_available 'cdwriter')" = "x" ] && \
+				write_rule "$match" "cdwriter"
+			[ "x$(find_next_available 'cdr')" = "x" ] && \
+				write_rule "$match" "cdr"
+			if [ "$ID_CDROM_CD_RW" ]; then
+				write_rule "$match" "cdrw$link_num"
+				[ "x$(find_next_available 'cdrw')" = "x" ] && \
+					write_rule "$match" "cdrw"
+				[ "x$(find_next_available 'writer')" = "x" ] && \
+					write_rule "$match" "writer"
+			fi
+			[ "x$(find_next_available 'writer')" = "x" ] && \
+				write_rule "$match" "writer"
+		fi
 
-link_num=$(find_next_available 'cdrom[0-9]*')
 
-match="ENV{ID_CDROM}==\"?*\", ENV{ID_PATH}==\"$ID_PATH\""
+	unlock_rules_file
 
-comment="$ID_MODEL ($ID_PATH)"
-
-	write_rule "$match" "cdrom$link_num" "$comment"
-[ "$ID_CDROM_CD_R" -o "$ID_CDROM_CD_RW" ] && \
-	write_rule "$match" "cdrw$link_num"
-[ "$ID_CDROM_DVD" ] && \
-	write_rule "$match" "dvd$link_num"
-[ "$ID_CDROM_DVD_R" -o "$ID_CDROM_DVD_RW" -o "$ID_CDROM_DVD_RAM" ] && \
-	write_rule "$match" "dvdrw$link_num"
-
-unlock_rules_file
-
-echo $SYMLINKS
+	echo $SYMLINKS
+fi
 
 exit 0
 

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Re: Some changes in write-cd-rules script

[md]

On Oct 26, Piter PUNK <piterpk@terra.com.br> wrote:

> 	I got the following problems:
Your first problem is that you do not understand the locking rules used
by the script.

> +if ! egrep "^ENV{ID_CDROM}=\"\?\*\", ENV{ID_PATH}=\"$ID_PATH\"" /etc/udev/rules.d/* &>/dev/null ; then 
> +	# Prevent concurrent processes from modifying the file at the same time.
> +	lock_rules_file

This creates a race.
Also, checking all files in the directory is broken because some may not
be rules files.

I think that there are other problems, but I have not examined carefully
the script.

-- 
ciao,
Marco

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Re: Some changes in write-cd-rules script

[Piter PUNK]

md wrote:
> Your first problem is that you do not understand the locking rules used
> by the script.
> 
>> +if ! egrep "^ENV{ID_CDROM}=\"\?\*\", ENV{ID_PATH}=\"$ID_PATH\"" /etc/udev/rules.d/* &>/dev/null ; then 
>> +	# Prevent concurrent processes from modifying the file at the same time.
>> +	lock_rules_file
> 
> This creates a race.

You are correct. The test needs to be after the lock_rules_file.
In our script (cdrom-symlinks.sh) it is after the locking.

> Also, checking all files in the directory is broken because some may not
> be rules files.

I don't know that. I was thinking udev looks in all files under
/etc/udev/rules.d. Now i test renaming some files to DONTRUN, README,
etc.. and it really doesn't read this files. Changing the grep to
*.rules will solve it.

> I think that there are other problems, but I have not examined carefully
> the script.

Good, i will be happy with your feedback.

							Piter PUNK
-- 
     |        E-Mail: piterpk@terra.com.br        (personal)
    .|.               roberto.batista@ntux.com.br (professional)
    /V\
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   ^`~'^         ----> Slackware Linux - The Best One! <----
  #105432

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