Re: Wishlist + bugs for udev-058

[Kay Sievers <kay.sievers@vrfy.org>]

On Tue, May 31, 2005 at 08:54:44PM +0200, Bodo Eggert wrote:
> 
> I tried to make udev create the following device nodes for my usb 
> stick(s):
> 
> /udev/usb/stick%E/disk
> /udev/usb/stick%E/part%n
> /udev/usb/stick%E/sg
> /udev/usb/stick%E/default -> part1, if -e part1
> /udev/usb/stick%E/default -> disk , otherwise
> 
> where %E is the same number for each node pointing to a given device, 
> starting with 0 (or 1, if you're a pascal programmer:).
> 
> The best I could do was usb/%k/* without "default", and I had to use some 
> very ugly tricks.

SCSI-devices are not numerically enumerated, so this will not work.
Well, device node enumeration in general is a very bad idea on systems
where devices can come and go at any time. Just forget the enumeration
and switch to a naming-scheme, that uses persistent/unique attributes.

> For those interested, I ended with:
> 
> BUS="usb", DRIVER="usb-storage", KERNEL="sg*", PROGRAM="/bin/sh -c 
>  '/usr/bin/readlink /sys/%p/device/block|/usr/bin/sed -e s,.\*/,,'" 
>  NAME="usb/%c/sg", GROUP="root", OWNER="root", Mode="600"
> BUS="usb", DRIVER="usb-storage", PROGRAM="/bin/bash -c 'a=%P;echo 
>  ${a%%/disk};[ $a ]'", NAME="%c/part%n", GROUP="users", OWNER="root", 
>  Mode="660"
> BUS="usb", DRIVER="usb-storage", NAME="usb/%k/disk", GROUP="users", 
>  OWNER="root", Mode\x0660
> 
> These are the missing features and the bugs I encountered while I tried:
> 
> Wish: Make sg devices be a child of their corresponding devices

That's a kernel thing. Try to convince the scsi-guys. :)

> Wish: Support really fprintf-like syntax
> 
> Bug: PROGRAM="/bin/sh -c '/usr/bin/readlink \
>  /sys/%p/device/block|/usr/bin/sed -e \
>  s,.\*/,,'" will be run with an empty extra parameter

Use a script for stuff like that.

> Wish: Comparing using !
Doesn't it work?

> Wish: Comparing and string replacement using extended regex 
>       (compiletime-optional)

Again, use a script if you need this. Udev supports only simple pattern
matching like fnmatch().

> Wish: Direct access to the "parent device" variable.

What does 'variable' mean? The name of the node?

> Wish: Query the existence and the number of partitions.

Look at sysfs for yourself. It's beyond the scope of udev.

> Wish: User variables. I'd like to use e.g. V{name}="foo", V{name}="foo" 
> and NAME="%v{name}"

Care to give a good real-world example why this is needed.

> Wish: Remove empty directories on unlinking device nodes

Doesn't it work?

> Bug?: SYSFS{removable}="1" is found for /block/sdd, but not for 
> /block/sdd/sdd1. Is that intentional?

How does the failing rule look like? You can match only against sysfs
files in one and the same directory. SYSFS{../removable} may work as a
bad trick. :)

> Bug: udev stops to honor rules containing NAME="foo" after it has found
> the first one. This behaviour is undocumentated.

Fixed with the next version.

> Misfeature: udevtest will not give debugging output unless udev will do 
> the same, and there is no way to get the debugging output without 
> reconfiguring syslog or changing the source code. If debugging is enabled, 
> the config parsing will be too chatty to be useful.

Compile with debug, disable debug in the config and try:
  UDEV_LOG=7 ./udevinfo ...

> Bug: Dependencies on logging.h are missing in the Makefile.

Fixed with the next version.

> Misfeature: Fancy make output on non-ttys, will mess up IDEs like jstar 
> and emacs.

pass V=1

Kay


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