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From: Martin Gregorie on 18 Dec 2008 09:08
On Thu, 18 Dec 2008 13:12:27 +0000, Theo Markettos wrote:

>
> Indeed. Depending on how old your distro is, it'll either be hotplug
> (quite old now) or udev. You'll have to look up the docs for each.
>
Thanks, guys. F8 and F9 are udev.

> On my work machine I have udev, with the following in a file in
> /etc/udev/rules.d/
>
> KERNEL=="ttyS0", NAME="%k", MODE="0667", OPTIONS="last_rule",
> OWNER="1941" (where '1941' is the numeric UID for my account)
>
> If you swap that for KERNEL=="ttyUSB[0-2]" that might do the trick. You
> might need to restart udev or reboot for this to take effect.
>
I found the following line in 50-udev-default.rules:

KERNEL=="tty[A-Z]*|pppox*|ircomm*|noz*", GROUP="uucp"

which looks to be the controlling rule for both ttyS[0-3] and ttyyUSB[0-9]
so I guess first cut says I should simply add

, MODE="0666"

to it. However, the file has a line warning that it shouldn't be modified
because it gets automatically overwritten and there's nothing in the
manpages to say how the rules should be modified. Can I simply put a
file, say

51-udev-local-override.rules

to the rules.d directory with my modified rule in it?


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martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
From: Geoffrey Clements on 18 Dec 2008 10:46
Martin Gregorie wrote:


[snip]

> I found the following line in 50-udev-default.rules:
>
> KERNEL=="tty[A-Z]*|pppox*|ircomm*|noz*", GROUP="uucp"
>
> which looks to be the controlling rule for both ttyS[0-3] and ttyyUSB[0-9]
> so I guess first cut says I should simply add
>
> , MODE="0666"
>
> to it. However, the file has a line warning that it shouldn't be modified
> because it gets automatically overwritten and there's nothing in the
> manpages to say how the rules should be modified. Can I simply put a
> file, say
>
> 51-udev-local-override.rules
>
> to the rules.d directory with my modified rule in it?
>
>

That should do it, just was out for any preceding rules which match this
device and specify a "last_rule" option.

You can use "udevadm test" to see what will happen.

--
Geoff Registered Linux user 196308
Replace bitbucket with geoff to mail me.
From: Martin Gregorie on 18 Dec 2008 14:31
On Thu, 18 Dec 2008 15:46:16 +0000, Geoffrey Clements wrote:

> That should do it, just was out for any preceding rules which match this
> device and specify a "last_rule" option.
>
> You can use "udevadm test" to see what will happen.

Thanks for the advice. Permissions are now being set just as I want them.

The rule ended up as:

KERNEL=="tty[A-Z]*", GROUP="uucp", MODE="0666", OPTIONS="last_rule"

in a separate file. I changed the match pattern so the rule only affects
serial ports and USB-serial adapters. At that point it fixed the USB-
serial adapter but not the ttyS* ports (and I still can't see why there's
a difference). After adding the "last_rule" option it fixes the
permissions on all the serial ports.

BTW, I think there's a misfeature in the udev pattern matcher:
"tty[A-Z]*" matches 'tty', 'ttyS0' and 'ttyUSB0' but not 'tty0'.
IOW its acting as though [A-Z]* means 'match at least one of the letters
A to Z or the end of the string' rather than the implied (and
conventional) 'zero or more characters'.

Can anybody give me the address of a person or group who should be told
about it?


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martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
From: Mike Civil on 18 Dec 2008 16:15
In article <gie8en$4tl$1(a)localhost.localdomain>,
Martin Gregorie <martin(a)see.sig.for.address.invalid> wrote:
>BTW, I think there's a misfeature in the udev pattern matcher:
>"tty[A-Z]*" matches 'tty', 'ttyS0' and 'ttyUSB0' but not 'tty0'.
>IOW its acting as though [A-Z]* means 'match at least one of the letters
>A to Z or the end of the string' rather than the implied (and
>conventional) 'zero or more characters'.

The udev docs do state that shell-style pattern patching is used, so it
seems to be working as documented :)

Mike
From: Martin Gregorie on 18 Dec 2008 17:31
On Thu, 18 Dec 2008 21:15:41 +0000, Mike Civil wrote:

> In article <gie8en$4tl$1(a)localhost.localdomain>, Martin Gregorie
> <martin(a)see.sig.for.address.invalid> wrote:
>>BTW, I think there's a misfeature in the udev pattern matcher:
>>"tty[A-Z]*" matches 'tty', 'ttyS0' and 'ttyUSB0' but not 'tty0'. IOW its
>>acting as though [A-Z]* means 'match at least one of the letters A to Z
>>or the end of the string' rather than the implied (and conventional)
>>'zero or more characters'.
>
> The udev docs do state that shell-style pattern patching is used, so it
> seems to be working as documented :)
>
OK, agreed.

I missed the rule giving a+rw permissions to /dev/tty in 50-udev-
default.rules because its not in the set labelled "# serial" and then
didn't look at the group assigned to that device. My mistake.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |
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