[gentoo-user] serial in /sys

[gentoo-user] serial in /sys

[Jorge Almeida]

Anyone knows how to dig into /sys to find the serial number of a device (say,
a USB pen)? I few days ago I found by trial and error something like
$ cat /sys/devices/pci0000:00/0000:00:06.1/usb2/2-4/2-4:1.0/host13/target13:0:0/13:0:0:0/block/sdc/../../../../../serial
which gave me E68911000519
Now I can't find nothing of the sort. (Yes, I know the path changes
each time the
device is plugged in, but even so)
Any information that would put some order into this mess would be great.

TIA

Joreg Almeida

Re: [gentoo-user] serial in /sys

[Marco Bonfiglio]

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2012/11/29 Jorge Almeida <jjalmeida@gmail.com>

> Anyone knows how to dig into /sys to find the serial number of a device
> (say,
> a USB pen)? I few days ago I found by trial and error something like
> $ cat
> /sys/devices/pci0000:00/0000:00:06.1/usb2/2-4/2-4:1.0/host13/target13:0:0/13:0:0:0/block/sdc/../../../../../serial
> which gave me E68911000519
> Now I can't find nothing of the sort. (Yes, I know the path changes
> each time the
> device is plugged in, but even so)
> Any information that would put some order into this mess would be great.
>
> TIA
>
> Joreg Almeida
>
>
If by "serial" you mean UUID I personally use "ls -l /dev/disk/by-uuid/"

Marco Bonfiglio

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Re: [gentoo-user] serial in /sys

[Jorge Almeida]

On Thu, Nov 29, 2012 at 6:35 PM, Marco Bonfiglio
<marco.bonfiglio@gmail.com> wrote:
>
>
> 2012/11/29 Jorge Almeida <jjalmeida@gmail.com>
>>
>> Anyone knows how to dig into /sys to find the serial number of a device
>> (say,
>> a USB pen)? I few days ago I found by trial and error something like
>> $ cat
>> /sys/devices/pci0000:00/0000:00:06.1/usb2/2-4/2-4:1.0/host13/target13:0:0/13:0:0:0/block/sdc/../../../../../serial
>> which gave me E68911000519
>> Now I can't find nothing of the sort. (Yes, I know the path changes
>> each time the
>> device is plugged in, but even so)
>> Any information that would put some order into this mess would be great.
>>
>> TIA
>>
>> Joreg Almeida
>>
>
> If by "serial" you mean UUID I personally use "ls -l /dev/disk/by-uuid/"
>
It is not the same thing, but anyway I have in /dev/disk/by-id/ a symlink
 usb-silicon_-power_E68911000519-0:0 -> ../../sdd

This is indeed the device I meant, and the serial number is the "E68911000519"
substring. But this symlink exists because udev created it. I need to somehow
dig it out of /sys, not out of /dev. IOW, how did udev retrieved the
information to create the symlink? The values of ../by-uuid/ would probably be
equally good, but I don't know how to find them any more than I know how to
find the serials...

Thanks

J.A.

Re: [gentoo-user] serial in /sys

[Bruce Hill]

On Thu, Nov 29, 2012 at 05:57:46PM +0000, Jorge Almeida wrote:
> Anyone knows how to dig into /sys to find the serial number of a device (say,
> a USB pen)? I few days ago I found by trial and error something like
> $ cat /sys/devices/pci0000:00/0000:00:06.1/usb2/2-4/2-4:1.0/host13/target13:0:0/13:0:0:0/block/sdc/../../../../../serial
> which gave me E68911000519
> Now I can't find nothing of the sort. (Yes, I know the path changes
> each time the
> device is plugged in, but even so)
> Any information that would put some order into this mess would be great.
> 
> TIA
> 
> Joreg Almeida

Why not look in dmesg output:

[871998.865035] usb 2-5: new high speed USB device number 4 using ehci_hcd
[871998.986925] usb 2-5: New USB device found, idVendor=13fe, idProduct=3600
[871998.986928] usb 2-5: New USB device strings: Mfr=1, Product=2,
SerialNumber=3
[871998.986930] usb 2-5: Product: patriot memory
[871998.986931] usb 2-5: Manufacturer:         
[871998.986932] usb 2-5: SerialNumber: 07B20F01654F84B8
[871998.987237] usb-storage 2-5:1.0: Quirks match for vid 13fe pid 3600: 4000
[871998.987257] scsi15 : usb-storage 2-5:1.0
[872000.021585] scsi 15:0:0:0: Direct-Access              patriot memory
PMAP PQ: 0 ANSI: 0 CCS
[872000.021983] sd 15:0:0:0: Attached scsi generic sg4 type 0
[872001.831285] sd 15:0:0:0: [sdd] 7811072 512-byte logical blocks: (3.99
GB/3.72 GiB)
[872001.831776] sd 15:0:0:0: [sdd] Write Protect is off
[872001.831779] sd 15:0:0:0: [sdd] Mode Sense: 23 00 00 00
[872001.832263] sd 15:0:0:0: [sdd] No Caching mode page present
[872001.832265] sd 15:0:0:0: [sdd] Assuming drive cache: write through
[872001.836389] sd 15:0:0:0: [sdd] No Caching mode page present
[872001.836392] sd 15:0:0:0: [sdd] Assuming drive cache: write through
[872001.870531]  sdd: sdd1
[872001.873413] sd 15:0:0:0: [sdd] No Caching mode page present
[872001.873415] sd 15:0:0:0: [sdd] Assuming drive cache: write through
[872001.873417] sd 15:0:0:0: [sdd] Attached SCSI removable disk
-- 
Happy Penguin Computers               >')
126 Fenco Drive                       ( \
Tupelo, MS 38801                       ^^
support@happypenguincomputers.com
662-269-2706 662-205-6424
http://happypenguincomputers.com/

Don't top-post: http://en.wikipedia.org/wiki/Top_post#Top-posting

Re: [gentoo-user] serial in /sys

[Jorge Almeida]

On Thu, Nov 29, 2012 at 7:20 PM, Bruce Hill
<daddy@happypenguincomputers.com> wrote:
> On Thu, Nov 29, 2012 at 05:57:46PM +0000, Jorge Almeida wrote:
>> Anyone knows how to dig into /sys to find the serial number of a device (say,
>> a USB pen)? I few days ago I found by trial and error something like
>> $ cat /sys/devices/pci0000:00/0000:00:06.1/usb2/2-4/2-4:1.0/host13/target13:0:0/13:0:0:0/block/sdc/../../../../../serial
>> which gave me E68911000519
>> Now I can't find nothing of the sort. (Yes, I know the path changes
>> each time the
>> device is plugged in, but even so)
>> Any information that would put some order into this mess would be great.
>>
>> TIA
>>
>> Joreg Almeida
>
> Why not look in dmesg output:

It is a matter of programming, not looking. I need a program that creates the
symlink when the device is plugged in. Think mdev (more precisely, a
complement to mdev that would take care of a few particular devices, to allow
using fstab to mount them in chosen mountpoints, and then leave the
rest to mdev).

Thanks

J.A.

Re: [gentoo-user] serial in /sys

[Bruce Hill]

On Thu, Nov 29, 2012 at 07:31:10PM +0000, Jorge Almeida wrote:
> 
> It is a matter of programming, not looking. I need a program that creates the
> symlink when the device is plugged in. Think mdev (more precisely, a
> complement to mdev that would take care of a few particular devices, to allow
> using fstab to mount them in chosen mountpoints, and then leave the
> rest to mdev).

Have you considered sys-apps/uam ?
-- 
Happy Penguin Computers               >')
126 Fenco Drive                       ( \
Tupelo, MS 38801                       ^^
support@happypenguincomputers.com
662-269-2706 662-205-6424
http://happypenguincomputers.com/

Don't top-post: http://en.wikipedia.org/wiki/Top_post#Top-posting

Re: [gentoo-user] serial in /sys

[Jorge Almeida]

On Thu, Nov 29, 2012 at 8:20 PM, Bruce Hill
<daddy@happypenguincomputers.com> wrote:
> On Thu, Nov 29, 2012 at 07:31:10PM +0000, Jorge Almeida wrote:
>>
>> It is a matter of programming, not looking. I need a program that creates the
>> symlink when the device is plugged in. Think mdev (more precisely, a
>> complement to mdev that would take care of a few particular devices, to allow
>> using fstab to mount them in chosen mountpoints, and then leave the
>> rest to mdev).
>
> Have you considered sys-apps/uam ?
> --
Didn't know about it. But it doesn't look promising. It requires udev (which
by itself would do what I want) and it's oriented towards automounting, which
I don't need nor want.

Thanks,

J.A.

Re: [gentoo-user] serial in /sys

[Kevin Chadwick]

> The values of ../by-uuid/ would probably be
> equally good, but I don't know how to find them any more than I know how to
> find the serials...

I use my own automounter scripts and udev with nice static mountpoints
from when udisks threw lots away for a while in favour of multiseat. A
recurring theme it seems!!! 

Incidentally I think I'm having issues accesing a dvd from a chroot due
to udisks and possibly due to not following the 'everythings a file'
mantra as thoggen falls back to /dev/dvd just fine and k9copy works only
in folder mode.

Does blkid -U work for you?

-- 
_______________________________________________________________________

'Write programs that do one thing and do it well. Write programs to work
together. Write programs to handle text streams, because that is a
universal interface'

(Doug McIlroy)
_______________________________________________________________________

Re: [gentoo-user] serial in /sys

[Walter Dnes]

On Thu, Nov 29, 2012 at 07:31:10PM +0000, Jorge Almeida wrote

> It is a matter of programming, not looking. I need a program that
> creates the symlink when the device is plugged in. Think mdev
> (more precisely, a complement to mdev that would take care of a few
> particular devices, to allow using fstab to mount them in chosen
> mountpoints, and then leave the rest to mdev).

  I have a couple of scripts that automount USB devices under mdev.  See
https://wiki.gentoo.org/wiki/Mdev for the general setup, and
https://wiki.gentoo.org/wiki/Mdev/Automount_USB and
https://wiki.gentoo.org/wiki/Mdev/Automount_USB/automount

  Once set up, "it just works".  If you want to go spelunking through
/sys for connected USB devices, here are a few hints.  I currently
have connected to my machine...
* a Dell keyboard
* a Logitech trackball mouse
* an external USB hard drive
* 2 USB keys

  The output below shows that not every USB device has a serial number,
and the "Patriot Memory" key has a serial number but no manufacturer...

[d531][waltdnes][~] find /sys/devices/pci0* -name serial | xargs cat
0000:00:1a.0
0000:00:1a.1
0000:00:1a.2
0000:00:1a.7
0000:00:1d.0
0000:00:1d.1
0000:00:1d.2
0000:00:1d.7
00000000000000070493
078215B00E5C
574341565530313435313431

[d531][waltdnes][~] find /sys/devices/pci0* -name manufacturer | xargs cat
Linux 3.3.8-gentoo uhci_hcd
Linux 3.3.8-gentoo uhci_hcd
Dell
Linux 3.3.8-gentoo uhci_hcd
Logitech
Linux 3.3.8-gentoo ehci_hcd
Linux 3.3.8-gentoo uhci_hcd
Linux 3.3.8-gentoo uhci_hcd
Linux 3.3.8-gentoo uhci_hcd
Linux 3.3.8-gentoo ehci_hcd
SanDisk Corporation
        
Western Digital

[d531][waltdnes][~] find /sys/devices/pci0* -name product | xargs cat
UHCI Host Controller
UHCI Host Controller
Dell USB Keyboard
2003
UHCI Host Controller
Trackball
c404
EHCI Host Controller
UHCI Host Controller
UHCI Host Controller
UHCI Host Controller
EHCI Host Controller
Cruzer Titanium
Patriot Memory  
My Book 1110


-- 
Walter Dnes <waltdnes@waltdnes.org>
We are apparently better off trying to avoid udev like the plague.
Linus Torvalds; 2012/10/03 https://lkml.org/lkml/2012/10/3/349

Re: [gentoo-user] serial in /sys

[Jorge Almeida]

On Thu, Nov 29, 2012 at 10:35 PM, Walter Dnes <waltdnes@waltdnes.org> wrote:
> On Thu, Nov 29, 2012 at 07:31:10PM +0000, Jorge Almeida wrote
>
>
>   I have a couple of scripts that automount USB devices under mdev.  See
> https://wiki.gentoo.org/wiki/Mdev for the general setup, and
> https://wiki.gentoo.org/wiki/Mdev/Automount_USB and
> https://wiki.gentoo.org/wiki/Mdev/Automount_USB/automount
>

I don't care for automounting, I just want customized symlinks. Using fstab is
not a second choice, it is how I want it.

>
>   The output below shows that not every USB device has a serial number,
> and the "Patriot Memory" key has a serial number but no manufacturer...
>
> [d531][waltdnes][~] find /sys/devices/pci0* -name serial | xargs cat
>

OK. I found that my pens have serial numbers. I setup /proc/sys/kernel/hotplug
with a script that prints the environment. When a pen is inserted, this is
what is set:

ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:04.1/usb1/1-4/1-4:1.0/host12/target12:0:0/12:0:0:0/block/sdd
SUBSYSTEM=block
MAJOR=8
MINOR=48
DEVNAME=sdd
DEVTYPE=disk
SEQNUM=1750

Following your suggestion:
# find /sys/devices/pci0* -name serial
/sys/devices/pci0000:00/0000:00:04.0/usb5/serial
/sys/devices/pci0000:00/0000:00:04.1/usb1/1-4/serial
/sys/devices/pci0000:00/0000:00:04.1/usb1/serial
/sys/devices/pci0000:00/0000:00:06.0/usb6/serial
/sys/devices/pci0000:00/0000:00:06.1/usb3/3-4/serial
/sys/devices/pci0000:00/0000:00:06.1/usb3/serial
/sys/devices/pci0000:00/0000:00:0c.0/0000:02:00.0/0000:03:01.0/0000:04:00.0/usb2/serial
/sys/devices/pci0000:00/0000:00:0c.0/0000:02:00.0/0000:03:01.0/0000:04:00.0/usb4/serial

# cat /sys/devices/pci0000:00/0000:00:04.1/usb1/1-4/serial
AA04012700011287

So, the serial number is here. To retrieve it out of $DEVPATH, I can do (in
this case, at least!):
# cat /sys/devices/pci0000:00/0000:00:04.1/usb1/1-4/1-4:1.0/host12/target12:0:0/12:0:0:0/block/sdd/../../../../../../serial
AA04012700011287

I'm assuming that this scenario is consistent for usb pen drives. I'll think
of external hard disks next...

BTW, the idea behind this is:
-- have s6-devd listen to the netlink interface
(http://www.skarnet.org/software/s6-linux-utils/s6-devd.html)

-- when a device is inserted, s6-devd launches a program that tries to obtain
the serial number, uses it as key to seek a string some_name in a constant
database, and creates the symlink /dev/some_name --> $DEVNAME. On failure,
exec mdev with the environment passed by the kernel.

I'm supposing that the environment on netlink is the same as with the hotplug
mechanism. Would this be true?

I would be interested in hearing any comments...

Thanks

Joreg Almeida

>
> --
> Walter Dnes <waltdnes@waltdnes.org>
> We are apparently better off trying to avoid udev like the plague.

Precisely.

> Linus Torvalds; 2012/10/03 https://lkml.org/lkml/2012/10/3/349
>

Re: [gentoo-user] serial in /sys

[James Cloos]

If you are looking for the serial number of a usb device, I find them at:

  /sys/bus/usb/devices/usb*/*/serial

NB that not all have them.

-JimC
-- 
James Cloos <cloos@jhcloos.com>         OpenPGP: 1024D/ED7DAEA6

Re: [gentoo-user] serial in /sys

[Walter Dnes]

On Fri, Nov 30, 2012 at 12:28:01AM +0000, Jorge Almeida wrote

> When a pen is inserted, this is what is set:
> 
> ACTION=add
> DEVPATH=/devices/pci0000:00/0000:00:04.1/usb1/1-4/1-4:1.0/host12/target12:0:0/12:0:0:0/block/sdd
> SUBSYSTEM=block
> MAJOR=8
> MINOR=48
> DEVNAME=sdd
> DEVTYPE=disk
> SEQNUM=1750

  [...deletia...]
 
> I'm supposing that the environment on netlink is the same as with the hotplug
> mechanism. Would this be true?

  This is almost exactly what I remember from when I was
writing/testing/debugging my automount scripts.  The one difference I
remember is that when mdev handled it, there was no "DEVNAME" variable,
but rather it was "MDEV".  But otherwise identical.  Two important notes...

1) For a USB mass storage device (pen or external hard drive) with N
partitions, the hotplug handler will get N+1 events when inserting and
also when removing.  E.g. if your pen drive has 3 partitions, you'll get
4 events...
* one for /dev/sdd
* one for /dev/sdd1
* one for /dev/sdd2
* one for /dev/sdd3

2) There is one exception to the above rule.  Sometimes, Windows will
format an entire pen as one large partition, without a partition table.
This requires an ugly hack in my script.  If DEVTYPE is "disk", it
checks for the string "FAT" in the first 512 bytes of the device
(bleagh).  Here's an excerpt from my script at
https://wiki.gentoo.org/wiki/Mdev/Automount_USB/automount

######################################################################
if [ "X${ACTION}" == "Xadd" ] ; then
#
# Flag for mounting if it's a regular partition
   if [ "X${DEVTYPE}" == "Xpartition" ] ; then
      partition=1 ;
#
# Further checks if DEVTYPE is disk; looking for weird setup where the
# entire USB key is formatted as one partition, without the standard
# partition table.
   elif [ "X${DEVTYPE}" == "Xdisk" ] ; then
#
# If it's "disk", check for string "FAT" in first 512 bytes of device.
# Flag as a partition if the string is found.
      if dd if=${MDEV} bs=512 count=1 2>/dev/null | grep "FAT" 1>/dev/null ; then
         partition=1
      fi
   fi
fi
######################################################################

  The important line is...
if dd if=${MDEV} bs=512 count=1 2>/dev/null | grep "FAT" 1>/dev/null ;


  Would you be OK if the devices were always mounted in /media ?  The
reason I ask is that my scripts use pmount, which can take an optional
label argument.  E.g. if MDEV is "sdd1"

pmount --umask 007 --noatime /dev/${MDEV}
would create /media/sdd1

pmount --umask 007 --noatime /dev/${MDEV} my_pendrive_1
would create /media/my_pendrive_1

  I always wanted to add that functionality to the scripts, but never
got around to it.

> BTW, the idea behind this is:
> -- have s6-devd listen to the netlink interface
> (http://www.skarnet.org/software/s6-linux-utils/s6-devd.html)
> 
> -- when a device is inserted, s6-devd launches a program that tries to
> obtain the serial number, uses it as key to seek a string some_name
> in a constant database, and creates the symlink /dev/some_name -->
> $DEVNAME. On failure, exec mdev with the environment passed by
> the kernel.

  The way I'm thinking of doing it is to...
* launch my script (with minor changes)
* on an "add" action invoke your program to look for a match
* if a match is found, use the optional label, otherwise use the default
  name in variable MDEV

  Actually, if I was writing it, I would add a few lines to my script
for the "add" ACTION
* label=${MDEV}
* look for a "serial" file in the PCI path of the newly-inserted device
* if found; then
     grep through a textfile to match the contents of the "serial" file
     if matched; then
        label=custom_name
        if [ ${#MDEV} -gt 3 ]; then
           label="${label}_${MDEV:3}"
        fi
     fi
  fi
  pmount --umask 007 --noatime /dev/${MDEV} ${label}

-- 
Walter Dnes <waltdnes@waltdnes.org>
We are apparently better off trying to avoid udev like the plague.
Linus Torvalds; 2012/10/03 https://lkml.org/lkml/2012/10/3/349

Re: [gentoo-user] serial in /sys

[Jorge Almeida]

On Fri, Nov 30, 2012 at 3:09 AM, Walter Dnes <waltdnes@waltdnes.org> wrote:
> On Fri, Nov 30, 2012 at 12:28:01AM +0000, Jorge Almeida wrote
>
>> When a pen is inserted, this is what is set:
>>
>> DEVNAME=sdd
>
>   This is almost exactly what I remember from when I was
> writing/testing/debugging my automount scripts.  The one difference I
> remember is that when mdev handled it, there was no "DEVNAME" variable,
> but rather it was "MDEV".  But otherwise identical.  Two important notes...

Strange. The variable name is set by the kernel. Maybe you were using a
patched kernel?

>
> 1) For a USB mass storage device (pen or external hard drive) with N
> partitions, the hotplug handler will get N+1 events when inserting and
> also when removing.  E.g. if your pen drive has 3 partitions, you'll get
> 4 events...

Right. The helper program is launched 4 times and will create (or remove,
depending on $ACTION) 4 symlinks.
>
>   Would you be OK if the devices were always mounted in /media ?  The
> reason I ask is that my scripts use pmount, which can take an optional
> label argument.  E.g. if MDEV is "sdd1"
>

pmount looks a good idea for a many-users workstation. For a 1-user computer,
there's no loss of functionality with sticking with fstab.

>
>   Actually, if I was writing it, I would add a few lines to my script
> for the "add" ACTION

Sure, I just didn't mention it.

> * label=${MDEV}
> * look for a "serial" file in the PCI path of the newly-inserted device
> * if found; then
>      grep through a textfile to match the contents of the "serial" file

I thought of keeping data-- (key,value) = (serial_number,
custom_name_of_device)-- in a cdb database. I think it is faster than reading
a text file, and no parsing needed. It is also scalable (although this is
probably irrelevant on a custom-workstation scale...). My (untested) program is
about 11k, statically compiled.

By the way, I don't suppose there is a mailing list to talk about these
matters (mdev/ udev-alternative/ udev-fork related)? This is really
distro-agnostic stuff...

Thanks

Jorge Almeida

Re: [gentoo-user] serial in /sys

[Neil Bothwick]

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On Thu, 29 Nov 2012 19:07:11 +0000, Jorge Almeida wrote:

> This is indeed the device I meant, and the serial number is the
> "E68911000519" substring. But this symlink exists because udev created
> it. I need to somehow dig it out of /sys, not out of /dev. IOW, how did
> udev retrieved the information to create the symlink?

This is all done in /usr/lib/udev/rules.d/60-persistent-storage.rules

ENV{SERIAL} seems to be the key, but udev rules use variables rather than
accessing /sys directly.

I really like udev as it makes just about anything you want to do easy,
it's a shame to watch it getting lost.


-- 
Neil Bothwick

Does someone know the cheats for WindowsXP?

[-- Attachment #2: signature.asc --]
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Re: [gentoo-user] serial in /sys

[Jorge Almeida]

On Fri, Nov 30, 2012 at 10:00 AM, Neil Bothwick <neil@digimed.co.uk> wrote:
> On Thu, 29 Nov 2012 19:07:11 +0000, Jorge Almeida wrote:
>
>> This is indeed the device I meant, and the serial number is the
>> "E68911000519" substring. But this symlink exists because udev created
>> it. I need to somehow dig it out of /sys, not out of /dev. IOW, how did
>> udev retrieved the information to create the symlink?
>
> This is all done in /usr/lib/udev/rules.d/60-persistent-storage.rules
>
> ENV{SERIAL} seems to be the key, but udev rules use variables rather than
> accessing /sys directly.

The point is what sets the variables. I don't think the kernel sets SERIAL, at
least it doesn't export it via the hotplug mechanism. Maybe it does it via
netlink, but where oh where is the documentation for that? Short of reading
the source, which is beyond my skills...

>
> I really like udev as it makes just about anything you want to do easy,
> it's a shame to watch it getting lost.
>
udev is a good idea, but it was plagued from the very beginning with the
syndrome "we know this arcane stuff, you don't need to understand as long as
your distro's devs can make it JustWork". Most users don't care, but some do,
as this is linux.

Cheers

Jorge Almeida

Re: [gentoo-user] serial in /sys

[Volker Armin Hemmann]

Am Donnerstag, 29. November 2012, 17:57:46 schrieb Jorge Almeida:
> Anyone knows how to dig into /sys to find the serial number of a device
> (say, a USB pen)? I few days ago I found by trial and error something like
> $ cat
> /sys/devices/pci0000:00/0000:00:06.1/usb2/2-4/2-4:1.0/host13/target13:0:0/1
> 3:0:0:0/block/sdc/../../../../../serial which gave me E68911000519
> Now I can't find nothing of the sort. (Yes, I know the path changes
> each time the
> device is plugged in, but even so)
> Any information that would put some order into this mess would be great.

why not just use lsusb -v for usb devices?

-- 
#163933

Re: [gentoo-user] serial in /sys

[Walter Dnes]

On Fri, Nov 30, 2012 at 09:58:10AM +0000, Jorge Almeida wrote
> On Fri, Nov 30, 2012 at 3:09 AM, Walter Dnes <waltdnes@waltdnes.org> wrote:
> 
> > 1) For a USB mass storage device (pen or external hard drive) with N
> > partitions, the hotplug handler will get N+1 events when inserting and
> > also when removing.  E.g. if your pen drive has 3 partitions, you'll get
> > 4 events...
> 
> Right. The helper program is launched 4 times and will create (or remove,
> depending on $ACTION) 4 symlinks.

  In my case, it would be 3 mounts.  There's no point in mounting the
underlying /dev/sdd, unless it happens to be the weird Windows format
where the entire device is a FAT partition, with no partition table.

> I thought of keeping data-- (key,value) = (serial_number,
> custom_name_of_device)-- in a cdb database. I think it is faster than
> reading a text file, and no parsing needed. It is also scalable
> (although this is probably irrelevant on a custom-workstation
> scale...). My (untested) program is about 11k, statically compiled.

  Come to think of it, I'd want to make it more general.  I'd have my
script read through a textfile ("flat-file database") with 3 columns.

1) Attribute; one of "manufacturer", "product", or "serial"; are there
   any others?

2) Value to match, i.e. manufacturer string, product name, or serial #.

3) The custom name I want my device to have

> By the way, I don't suppose there is a mailing list to talk about these
> matters (mdev/ udev-alternative/ udev-fork related)? This is really
> distro-agnostic stuff...

  For mdev-related questions, the best place I know of is the busybox
mailing list http://lists.busybox.net/mailman/listinfo/busybox  mdev is
part of busybox.

-- 
Walter Dnes <waltdnes@waltdnes.org>

Re: [gentoo-user] serial in /sys

[Joshua Murphy]

On Fri, Nov 30, 2012 at 10:47 PM, Walter Dnes <waltdnes@waltdnes.org> wrote:
> On Fri, Nov 30, 2012 at 09:58:10AM +0000, Jorge Almeida wrote
>> By the way, I don't suppose there is a mailing list to talk about these
>> matters (mdev/ udev-alternative/ udev-fork related)? This is really
>> distro-agnostic stuff...
>
>   For mdev-related questions, the best place I know of is the busybox
> mailing list http://lists.busybox.net/mailman/listinfo/busybox  mdev is
> part of busybox.
>
> --
> Walter Dnes <waltdnes@waltdnes.org>


And, while auto-mounting might be a bit beyond the 'official' scope of
it, I've seen a fair bit of recent chatter on the LFS mailing lists on
the general topic of device management, alongside a bit of grumbling
about the kitchen sink approach being taken with systemd/udev/etc.
Might be worth glancing through their archives to see if anything on
this particular question crops up, and if nothing else, it shouldn't
hurt much if you toss the question towards the lfs-chat list.

-- 
Poison [BLX]
Joshua M. Murphy

Re: [gentoo-user] serial in /sys

[Jorge Almeida]

On Sat, Dec 1, 2012 at 3:47 AM, Walter Dnes <waltdnes@waltdnes.org> wrote:
> On Fri, Nov 30, 2012 at 09:58:10AM +0000, Jorge Almeida wrote
>> On Fri, Nov 30, 2012 at 3:09 AM, Walter Dnes <waltdnes@waltdnes.org> wrote:
>>
>
>> I thought of keeping data-- (key,value) = (serial_number,
>> custom_name_of_device)-- in a cdb database. I think it is faster than
>> reading a text file, and no parsing needed. It is also scalable
>> (although this is probably irrelevant on a custom-workstation
>> scale...). My (untested) program is about 11k, statically compiled.
>
>   Come to think of it, I'd want to make it more general.  I'd have my
> script read through a textfile ("flat-file database") with 3 columns.
>
> 1) Attribute; one of "manufacturer", "product", or "serial"; are there
>    any others?
>

I checked that netlink and hotplug export exactly the same variables (well, at
least for the devices I tried), but SERIAL is not one of them, one has to dig
/sys. But the location of the "serial" file seems to be consistent, so problem
solved.

> 2) Value to match, i.e. manufacturer string, product name, or serial #.
>
> 3) The custom name I want my device to have
>

The problem with that approach is that the code is much less simple, and the
program less lean. I don't know what that implies regarding efficiency, but
inserting a usb pen with only one partition gives rise to 12 (!) events, and
thus the program (and hence mdev) is run 12 times, 10 of which are probably
completely useless (but there's no helping that).

You could have 3 cdb files, one for each type of key ("manufacturer",...) and
have the program seek them sequentially. It would still be very fast
(faster?), and less error prone. (I know cdb is not the most widely known type
of database, but it really is the appropriate one for this kind of usage--read
many times, write once in a blue moon--and it is very easy to deal with. I'm
using tinycdb (http://www.corpit.ru/mjt/tinycdb.html) because it provides a
library interface.)

>> By the way, I don't suppose there is a mailing list to talk about these
>> matters (mdev/ udev-alternative/ udev-fork related)? This is really
>> distro-agnostic stuff...
>
>   For mdev-related questions, the best place I know of is the busybox
> mailing list http://lists.busybox.net/mailman/listinfo/busybox  mdev is
> part of busybox.
>
OK, I just feel that mdev-related questions are really somewhat related, for
example, with the recent intentions of forking udev (which I hope will be
successful). For example, the evdev xorg driver requires udev! Is there a
really good reason for this, or is it another way to make udev mandatory? (A
bit of paranoia...) I don't know what list would be appropriate to raise this
question in.

Jorge Almeida

Re: [gentoo-user] serial in /sys

[Jorge Almeida]

On Sat, Dec 1, 2012 at 4:55 AM, Joshua Murphy <poisonbl@gmail.com> wrote:
> On Fri, Nov 30, 2012 at 10:47 PM, Walter Dnes <waltdnes@waltdnes.org> wrote:
>> On Fri, Nov 30, 2012 at 09:58:10AM +0000, Jorge Almeida wrote
>>> By the way, I don't suppose there is a mailing list to talk about these
>>> matters (mdev/ udev-alternative/ udev-fork related)? This is really
>>> distro-agnostic stuff...
>>
>>   For mdev-related questions, the best place I know of is the busybox
>> mailing list http://lists.busybox.net/mailman/listinfo/busybox  mdev is
>> part of busybox.
>
> And, while auto-mounting might be a bit beyond the 'official' scope of
> it, I've seen a fair bit of recent chatter on the LFS mailing lists on
> the general topic of device management, alongside a bit of grumbling
> about the kitchen sink approach being taken with systemd/udev/etc.
> Might be worth glancing through their archives to see if anything on
> this particular question crops up, and if nothing else, it shouldn't
> hurt much if you toss the question towards the lfs-chat list.
>
I'm subscribed to the lfs lists (I'm not sure about lfs-chat, though) for
years. I'll have a look.

Thanks

Jorge Almeida