[gentoo-user] How to set udev rule?

[gentoo-user] How to set udev rule?

[Song Zhiwei]

Hi all,

I complied a driver esdcan_usb331.so. I'd like use udev to create
character devices /dev/can0 and /dev/can1 with major 50 and minor 0/1
for the driver. How to write the udev rule for it?

The dmesg is:
esd CAN driver: CAN_USB331
esd CAN driver: baudrate not set
esd CAN driver: mode = 0x00000000, major = 50, verbose = 0x00000001
esd CAN driver: version 3.8.3 06:03:32 Aug 24 2009: successfully loaded
usbcore: registered new interface driver CAN_USB331

Re: [gentoo-user] How to set udev rule?

[KH]

Song Zhiwei schrieb:
> Hi all,
> 
> I complied a driver esdcan_usb331.so. I'd like use udev to create
> character devices /dev/can0 and /dev/can1 with major 50 and minor 0/1
> for the driver. How to write the udev rule for it?
> 
> The dmesg is:
> esd CAN driver: CAN_USB331
> esd CAN driver: baudrate not set
> esd CAN driver: mode = 0x00000000, major = 50, verbose = 0x00000001
> esd CAN driver: version 3.8.3 06:03:32 Aug 24 2009: successfully loaded
> usbcore: registered new interface driver CAN_USB331
> 

Hi,

there are two good guides for this:

http://www.gentoo.org/doc/en/udev-guide.xml
http://www.reactivated.net/writing_udev_rules.html

Regards kh

Re: [gentoo-user] How to set udev rule?

[Song Zhiwei]

Actually, I have read the guilds and tried, but it didnot work. So I asked here.

Two devices related with "can usb" were found when I used the udevadm:

#udevadm info -a -p /sys/devices/pci0000\:00/0000\:00\:0f.4/usb2/2-
2/2-2\:1.0
  looking at device '/devices/pci0000:00/0000:00:0f.4/usb2/2-2/2-2:1.0':
    KERNEL=="2-2:1.0"
    SUBSYSTEM=="usb"
    DRIVER=="CAN_USB331"
    ATTR{bInterfaceNumber}=="00"
    ATTR{bAlternateSetting}==" 0"
    ATTR{bNumEndpoints}=="04"
    ATTR{bInterfaceClass}=="00"
    ATTR{bInterfaceSubClass}=="00"
    ATTR{bInterfaceProtocol}=="00"
    ATTR{modalias}=="usb:v0AB4p0001d0002dc00dsc00dp00ic00isc00ip00"

  looking at parent device '/devices/pci0000:00/0000:00:0f.4/usb2/2-2':
    KERNELS=="2-2"
    SUBSYSTEMS=="usb"
    DRIVERS=="usb"
    ATTRS{configuration}==""
    ATTRS{bNumInterfaces}==" 1"
    ATTRS{bConfigurationValue}=="1"
    ATTRS{bmAttributes}=="80"
    ATTRS{bMaxPower}=="500mA"
    ATTRS{urbnum}=="20"
    ATTRS{idVendor}=="0ab4"
    ATTRS{idProduct}=="0001"
    ATTRS{bcdDevice}=="0002"
    ATTRS{bDeviceClass}=="00"
    ATTRS{bDeviceSubClass}=="00"
    ATTRS{bDeviceProtocol}=="00"
    ATTRS{bNumConfigurations}=="1"
    ATTRS{bMaxPacketSize0}=="16"
    ATTRS{speed}=="12"
    ATTRS{busnum}=="2"
    ATTRS{devnum}=="2"
    ATTRS{version}==" 1.00"
    ATTRS{maxchild}=="0"
    ATTRS{quirks}=="0x0"
    ATTRS{authorized}=="1"
    ATTRS{manufacturer}=="esd-gmbh"
    ATTRS{product}=="CAN-USB 543"
    ATTRS{serial}=="GD001494"

The module was loaded by an alias in /etc/modules.d/esdcan:
alias char-major-50 esdcan-usb331
But I cannot find the major:minor informations in the udev info above.

I tried the rules:
SUBSYSTEM=="usb", DRIVER=="CAN_USB331", ATTR{serial}=="GD001494", NAME="can0"
SUBSYSTEM=="usb", DRIVER=="CAN_USB331", NAME="can0"
DRIVER=="CAN_USB331", NAME="can0"
and
SUBSYSTEM=="usb", ATTR{serial}=="GD001494", NAME="can%n"
But any one of them does not work.

Anyone can help me?


2009/8/27 KH <gentoo-user@konstantinhansen.de>:
> Song Zhiwei schrieb:
>> Hi all,
>>
>> I complied a driver esdcan_usb331.so. I'd like use udev to create
>> character devices /dev/can0 and /dev/can1 with major 50 and minor 0/1
>> for the driver. How to write the udev rule for it?
>>
>> The dmesg is:
>> esd CAN driver: CAN_USB331
>> esd CAN driver: baudrate not set
>> esd CAN driver: mode = 0x00000000, major = 50, verbose = 0x00000001
>> esd CAN driver: version 3.8.3 06:03:32 Aug 24 2009: successfully loaded
>> usbcore: registered new interface driver CAN_USB331
>>
>
> Hi,
>
> there are two good guides for this:
>
> http://www.gentoo.org/doc/en/udev-guide.xml
> http://www.reactivated.net/writing_udev_rules.html
>
> Regards kh
>
>

Re: [gentoo-user] How to set udev rule?

[David Relson]

Don't know if the following will help, but it's a rule that I
successfully use to mount a USB memory stick:

 BUS=="usb", SYSFS{manufacturer}=="STECH", SYMLINK+="STECH", run+="/bin/mount -a"

Re: [gentoo-user] How to set udev rule?

[Alex Schuster]

David Relson writes:

> Don't know if the following will help, but it's a rule that I
> successfully use to mount a USB memory stick:
>
>  BUS=="usb", SYSFS{manufacturer}=="STECH", SYMLINK+="STECH",
> run+="/bin/mount -a"

I have to change the bus from usb to scsi, then it works. But what about 
unmounting? Is is possible to have it unmounted after I pull the memory 
stick?

	Wonko

Re: [gentoo-user] How to set udev rule?

[Dirk Heinrichs]

[-- Attachment #1: Type: Text/Plain, Size: 345 bytes --]

Am Sonntag 30 August 2009 19:29:39 schrieb Alex Schuster:

> I have to change the bus from usb to scsi, then it works. But what about
> unmounting? Is is possible to have it unmounted after I pull the memory
> stick?

How do want to umount something that's not there anymore? You have to umount 
_before_ you pull it.

Bye...

	Dirk

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 190 bytes --]

Re: [gentoo-user] How to set udev rule?

[Jesús Guerrero]

On Sun, August 30, 2009 21:38, Dirk Heinrichs wrote:
> Am Sonntag 30 August 2009 19:29:39 schrieb Alex Schuster:
>
>
>> I have to change the bus from usb to scsi, then it works. But what
>> about unmounting? Is is possible to have it unmounted after I pull the
>> memory stick?
>
> How do want to umount something that's not there anymore? You have to
> umount _before_ you pull it.

You can force the umount using -l (no, it's not documented in the man
page). You can use this to umount a volume *after* it has been physically
removed. And some people use this crap on udev rules to remove the
volume when they unplug the pendrive. Then they wonder why the heck
the file is not where it should be. I guess they never heard of cached
writes.

The correct thing to do is of course to umount it before,
and then unplug it or whatever.

If you truly want to umount after, you should at least do a sync before
removing the device. In any case, if you don't follow the logical
order of the things don't complain if then you find that the files that
should be there are not there when you need them.

If you truly love risk, just use umount -l, but you have to promise not
to cry if the fs breaks or your files are not writen when you sudenly
unplug the device.

-- 
Jesús Guerrero

Re: [gentoo-user] How to set udev rule?

[Dale]

Jesús Guerrero wrote:
> On Sun, August 30, 2009 21:38, Dirk Heinrichs wrote:
>   
>> Am Sonntag 30 August 2009 19:29:39 schrieb Alex Schuster:
>>
>>
>>     
>>> I have to change the bus from usb to scsi, then it works. But what
>>> about unmounting? Is is possible to have it unmounted after I pull the
>>> memory stick?
>>>       
>> How do want to umount something that's not there anymore? You have to
>> umount _before_ you pull it.
>>     
>
> You can force the umount using -l (no, it's not documented in the man
> page). You can use this to umount a volume *after* it has been physically
> removed. And some people use this crap on udev rules to remove the
> volume when they unplug the pendrive. Then they wonder why the heck
> the file is not where it should be. I guess they never heard of cached
> writes.
>
> The correct thing to do is of course to umount it before,
> and then unplug it or whatever.
>
> If you truly want to umount after, you should at least do a sync before
> removing the device. In any case, if you don't follow the logical
> order of the things don't complain if then you find that the files that
> should be there are not there when you need them.
>
> If you truly love risk, just use umount -l, but you have to promise not
> to cry if the fs breaks or your files are not writen when you sudenly
> unplug the device.
>
>   

Basically, if he is going to do this the way he is thinking of doing it,
use cp NOT mv.  o_O  If he uses mv and then unpkugs it without
unmounting or syncing, the file is gone for good.  At least with cp you
still have the original file.

Just thinking this through a little here.

Dale

:-)  :-) 

Re: [gentoo-user] How to set udev rule?

[Alex Schuster]

Jesús Guerrero writes:

> On Sun, August 30, 2009 21:38, Dirk Heinrichs wrote:
> > Am Sonntag 30 August 2009 19:29:39 schrieb Alex Schuster:
> >> I have to change the bus from usb to scsi, then it works. But what
> >> about unmounting? Is is possible to have it unmounted after I pull the
> >> memory stick?
> >
> > How do want to umount something that's not there anymore? You have to
> > umount _before_ you pull it.
>
> You can force the umount using -l (no, it's not documented in the man
> page). You can use this to umount a volume *after* it has been physically
> removed.

The -l is not necessary here, a simple umount is enough.

> And some people use this crap on udev rules to remove the
> volume when they unplug the pendrive. 

Yes, this very rule would be nice to have :)

> Then they wonder why the heck
> the file is not where it should be. I guess they never heard of cached
> writes.
>
> The correct thing to do is of course to umount it before,
> and then unplug it or whatever.

I do so, it makes me feel better, but I wonder whether it is _really_ 
necessary. I see Windows users do this all the time, without any problem 
yet. Of course, the wait a little after writing to it, but a few seconds 
after the blinking stops seem to be enough. And people are lazy, I know my 
Linux users _will_ just plug the stick. Using the KDE4 automounter, the 
device will be unmounted automatically in this case, but I am looking for a 
solution without KDE4, and as few user interaction as possible. The udev 
mouting rule is nice, but it leaves a lot of mounts when plugging in and out 
repeatedly.

When the system is mostly idle, I guess the writing to the stick would not 
be delayed for a long time, so this should be quite safe. At least if the 
data is not that important. And if there are no writes, I see no problem at 
all.

There also is the sync option to mount, it should not be used on media with 
limited number of write cycles, but I also guess that for my purposes this 
would not matter.

	Wonko

Re: [gentoo-user] How to set udev rule?

[Jesús Guerrero]

On Sun, August 30, 2009 23:26, Alex Schuster wrote:
> Jesús Guerrero writes:
>
>
>> Then they wonder why the heck
>> the file is not where it should be. I guess they never heard of cached
>> writes.
>>
>> The correct thing to do is of course to umount it before,
>> and then unplug it or whatever.
>
> I do so, it makes me feel better, but I wonder whether it is _really_
> necessary.

It is. Nothing can guarantee that the data has been dumped to the disk
unless you umount it first. You can reduce the chances of losing
information by waiting before removing it. But if the system is loaded
the writes can be deferred to a later time, when the system is idle.
This can be partially mitigated by using the "sync" mount option, as
you say below. :)

Of course then the performance will drop, and the i/o scheduler will
not have a chance to work as usual either because i/o ops will not be
queued, which is the bad part of the deal.


> I see Windows users do this all the time, without any problem
> yet. Of course, the wait a little after writing to it, but a few seconds
> after the blinking stops seem to be enough.

Lucky guys. That, or when the file is not on the drive they come back
and copy it again without you noticing it. This happens lots of times.
I've seen it and I'll continue to see it as long as users don't
understand what's going under the hood. That's what the safe removal
feature in Windows is about, it's not there just to decorate your
try, it exists for a reason.

> And people are lazy,

Yes, I am as well. But when integrity matters you really want to umount
or at least sync before unplugging. I am a lazy guy, lazy like hell, but
I always fasten my seat belt when I am going to drive. ;)

> The
> udev mouting rule is nice, but it leaves a lot of mounts when plugging in
> and out repeatedly.

Mmmm, I am not sure I follow you. If you use a rule as described above
you can remove the mount and even the mount point when the device is
detached. Is not that what you mean?

> When the system is mostly idle, I guess the writing to the stick would
> not be delayed for a long time, so this should be quite safe. At least if
> the data is not that important. And if there are no writes, I see no
> problem at all.

If you don't have a problem with the chance to lose files that's ok. I
just thought I'd point it out just in case, because the chance is there.
A write operation can be deferred for a number of reasons. That's why
"sync" (both as a command and as a mount option) was invented in first
place.

> There also is the sync option to mount, it should not be used on media
> with limited number of write cycles, but I also guess that for my purposes
> this would not matter.

Nowadays this shouldn't matter too much. The life cycle of ssd devices
has been greatly expanded, and they also do some kind of balancing so
all the blocks get the same usage. Even journal fs's shouldn't be much
of a problem with any recent flash device.

-- 
Jesús Guerrero

Re: [gentoo-user] How to set udev rule?

[Stroller]

On 31 Aug 2009, at 06:38, Jesús Guerrero wrote:
> ...
>> I see Windows users do this all the time, without any problem
>> yet. Of course, the wait a little after writing to it, but a few  
>> seconds
>> after the blinking stops seem to be enough.
>
> Lucky guys. That, or when the file is not on the drive they come back
> and copy it again without you noticing it. This happens lots of times.
> I've seen it and I'll continue to see it as long as users don't
> understand what's going under the hood. That's what the safe removal
> feature in Windows is about, it's not there just to decorate your
> try, it exists for a reason.

Indeed.

Macs complain if you pull a USB drive without safely removing it  
first, and this warns users against doing it again in the future.

The problem with XP is that the "safely remove" icon is so small that  
typical users don't ever notice it, and consequently don't know any  
better. They're used to hot-plugging USB mice, keyboards & printers  
into & from their laptops, so they don't see why a USB drive should be  
any different. XP doesn't complain about a USB drive unsafely removed;  
Vista's "safely remove" is slightly more obvious (available from a  
right-click menu) but I don't know if any other improvements (IMO a  
warning is important) have been made in Vista or Windows 7.

Windows does have an option which implies immediate syncs to USB  
drives, and I'd guess that if this is selected the copy or save file  
dialogues should remain on the screen until the whole file has been  
written, thus discouraging the user from unplugging the drive mid- 
write. I'm sceptical, however.

Stroller.

Re: [gentoo-user] How to set udev rule?

[Dirk Heinrichs]

[-- Attachment #1: Type: Text/Plain, Size: 2354 bytes --]

Am Sonntag 30 August 2009 23:26:52 schrieb Alex Schuster:
> Jesús Guerrero writes:
> > On Sun, August 30, 2009 21:38, Dirk Heinrichs wrote:
> > > Am Sonntag 30 August 2009 19:29:39 schrieb Alex Schuster:
> > >> I have to change the bus from usb to scsi, then it works. But what
> > >> about unmounting? Is is possible to have it unmounted after I pull the
> > >> memory stick?
> > >
> > > How do want to umount something that's not there anymore? You have to
> > > umount _before_ you pull it.
> >
> > You can force the umount using -l (no, it's not documented in the man
> > page). You can use this to umount a volume *after* it has been physically
> > removed.
>
> The -l is not necessary here, a simple umount is enough.
>
> > And some people use this crap on udev rules to remove the
> > volume when they unplug the pendrive.
>
> Yes, this very rule would be nice to have :)

No, it would not. It can (and most likely will) lead to data loss.

> I do so, it makes me feel better, but I wonder whether it is _really_
> necessary.

Yes, it is. You never know when your data is written to physical storage 
unless you explicitely synced or umounted it while the device was still 
connected.

> I see Windows users do this all the time, without any problem
> yet. Of course, the wait a little after writing to it, but a few seconds
> after the blinking stops seem to be enough.

Usually it is, but you never know. Windows users don't have that broad choice 
of filesystems. They have NTFS and that's it, so they may know they're save. 
Linux filesystems may handle this differently, depending on which one you've 
chosen.

> And people are lazy, I know my
> Linux users _will_ just plug the stick. Using the KDE4 automounter, the
> device will be unmounted automatically in this case,

You mount filesystems, not devices. If you plug the device which holds the 
filesystem you've mounted, the fs can't be umounted anymore. There's nothing 
KDE automounter (aka HAL/DBUS) can do about it.

> but I am looking for a
> solution without KDE4, and as few user interaction as possible. The udev
> mouting rule is nice, but it leaves a lot of mounts when plugging in and
> out repeatedly.

Use the kernel automounter (autofs). It also umounts automatically (after a 
configurable time).

Bye...

	Dirk

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 190 bytes --]

Re: [gentoo-user] How to set udev rule?

[Mick]

[-- Attachment #1: Type: text/plain, Size: 884 bytes --]

On Monday 31 August 2009, Dirk Heinrichs wrote:
> > I see Windows users do this all the time, without any problem
> > yet. Of course, the wait a little after writing to it, but a few seconds
> > after the blinking stops seem to be enough.
>
> Usually it is, but you never know. Windows users don't have that broad
> choice of filesystems. They have NTFS and that's it, so they may know
> they're save. Linux filesystems may handle this differently, depending on
> which one you've chosen.

Nope, NTFS can't cure user stupidity.  Only a couple of days ago a friend at 
work was reprimanded for not clicking on "safely remove", or whatever it's 
called in WinXP, after I used photorec to recover 350 photographs that she 
managed to 'lose' from her USB stick.

I bet she won't remove another USB drive without unmounting first in a 
haste ...  ;-)
-- 
Regards,
Mick

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 198 bytes --]