Ubuntu
udev package

Add udev rule to allow users to use Freescale VPU on ARM MX51 SoC based devices

Bug #340796 reported by Jerone Young
10
Affects Status Importance Assigned to Milestone
udev (Ubuntu)
Invalid
Wishlist
Scott James Remnant (Canonical)

Bug Description

For ARM based Fresscale MX51 SoCs. There is a VPU (video processing unit) that is exposed via the mxc driver. The device node by default only gives root access to this device. Adding a file:

/etc/udev/rules.d/40-fsl-permissions.rules:
# Miscellaneous devices
KERNEL=="mxc_vpu", MODE="0666"
SUBSYSTEM=="video", MODE="0666"

This will allow all users to be able to run software that can take advantage of the vpu.

Tags: armel imx51
Revision history for this message
Jerone Young (jerone) wrote :

Oh to comment that the patches for this chip are in our 2.6.28 tree and will soon be making there way upstream. So you may want to hold off submitting this udev rule upstream, and only keeping it in Ubuntu for now.

Revision history for this message
Scott James Remnant (Canonical) (canonical-scott) wrote :

We don't ship any rules not provided by Upstream I'm afraid.

If they aren't kernel upstream, they won't get applied

Revision history for this message
Scott James Remnant (Canonical) (canonical-scott) wrote :

Note that at least one of those rules is utterly and dangerously wrong.

Revision history for this message
Scott James Remnant (Canonical) (canonical-scott) wrote :

Please supply more details about this chip, the device driver, and the device nodes is actually creates.

Changed in udev:
assignee: nobody → scott
importance: Undecided → Wishlist
status: New → Incomplete
Revision history for this message
Adam Buchbinder (adam-buchbinder) wrote :

>Note that at least one of those rules is utterly and dangerously wrong.

Scott, can you provide a bit more information? It seems like there's something informative about writing udev rules that I'm missing.

Revision history for this message
Scott James Remnant (Canonical) (canonical-scott) wrote : Re: [Bug 340796] Re: Add udev rule to allow users to use Freescale VPU on ARM MX51 SoC based devices

On Mon, 2009-03-16 at 15:19 +0000, Adam Buchbinder wrote:

> >Note that at least one of those rules is utterly and dangerously wrong.
>
> Scott, can you provide a bit more information? It seems like there's
> something informative about writing udev rules that I'm missing.
>
The following rule:

 SUBSYSTEM=="video", MODE="0666"

matches all devices from the "video" subsystem, and grants full
read/write permissions to every single user and group for them.

That is most definitely *not* an acceptable default.

Also the "mxc_vpu" rule you give grants read/write to everyone - if
multiple users are logged in, or anyone logs in from ssh, they too can
also use this device.

In some cases, this is entirely ok - but it needs careful justification.

Scott
--
Scott James Remnant
<email address hidden>

Revision history for this message
Scott James Remnant (Canonical) (canonical-scott) wrote :

Please supply the requested information

Changed in udev (Ubuntu):
status: Incomplete → Invalid
Loïc Minier (lool)
tags: added: armel imx51
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