Question on how to get custom kernel module to work with udev

Question on how to get custom kernel module to work with udev

[Terry Barnaby]

Hi,

I have a custom kernel device driver module for a PCI hardware device that I would like
to integrate with UDEV to get UDEV to generate the /dev nodes.

I am using Fedora Core 3.
I have not been able to make this work so far, so any ideas ?

When the device is loaded /sbin/hotplug is called with the environment:

export SUBSYSTEM=drivers
export DEVPATH=/bus/pci/drivers/admxrc2
export PATH=/sbin:/bin:/usr/sbin:/usr/bin
export ACTION­d
export PWD=/
export SHLVL=1
export HOME=/
export SEQNUMx5
export _=/bin/env

I have added a file /etc/udev/rules.d/40-admxrc.rules with the contents:

KERNEL="admxrc2", NAME="admxrcii%k"
SYSFS{vendor}="0x4144", NAME="admxrciii%k"

The two line are alternate versions for testing.

I have tried setting the udev config parameter "udev_log" to "yes" and
do get logs when other drivers are loaded. However when I do a
"rmmod admxrc2; modprobe admxrc2" no log information is printed.

1. Is there a way to get more debug information out of udev ?
2. Is there some special thing I need to do in the device module ?
3. Is there something wround with the configuration ?

Cheers

Terry


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Re: Question on how to get custom kernel module to work with udev

[Terry Barnaby]

Terry Barnaby wrote:
> Hi,
> 
> I have a custom kernel device driver module for a PCI hardware device 
> that I would like
> to integrate with UDEV to get UDEV to generate the /dev nodes.
> 
> I am using Fedora Core 3.
> I have not been able to make this work so far, so any ideas ?
> 
> When the device is loaded /sbin/hotplug is called with the environment:
> 
> export SUBSYSTEM=drivers
> export DEVPATH=/bus/pci/drivers/admxrc2
> export PATH=/sbin:/bin:/usr/sbin:/usr/bin
> export ACTION­d
> export PWD=/
> export SHLVL=1
> export HOME=/
> export SEQNUMx5
> export _=/bin/env
> 
> I have added a file /etc/udev/rules.d/40-admxrc.rules with the contents:
> 
> KERNEL="admxrc2", NAME="admxrcii%k"
> SYSFS{vendor}="0x4144", NAME="admxrciii%k"
> 
> The two line are alternate versions for testing.
> 
> I have tried setting the udev config parameter "udev_log" to "yes" and
> do get logs when other drivers are loaded. However when I do a
> "rmmod admxrc2; modprobe admxrc2" no log information is printed.
> 
> 1. Is there a way to get more debug information out of udev ?
> 2. Is there some special thing I need to do in the device module ?
> 3. Is there something wround with the configuration ?
> 
> Cheers
> 
> Terry
> 
> 
> -------------------------------------------------------
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Some more information on this:

I have enabled debugiing in the udev sources and now see an error displayed
in the /var/log/messages file:

Jun  3 14:31:07 beam1 udev[15275]: main: looking at '/bus/pci/drivers/admxrc2'
Jun  3 14:31:07 beam1 udev[15275]: main: not a block or class device

This seems to sugest that I need to do something specific in the device
driver module to get udev to work ???

Terry



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Re: Question on how to get custom kernel module to work with udev

[Kay Sievers]

On Fri, Jun 03, 2005 at 02:24:44PM +0100, Terry Barnaby wrote:
> Hi,
> 
> I have a custom kernel device driver module for a PCI hardware device that 
> I would like
> to integrate with UDEV to get UDEV to generate the /dev nodes.

Is the source of the driver available?

Kay


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Re: Question on how to get custom kernel module to work with udev

[Terry Barnaby]

Kay Sievers wrote:
> On Fri, Jun 03, 2005 at 02:24:44PM +0100, Terry Barnaby wrote:
> 
>>Hi,
>>
>>I have a custom kernel device driver module for a PCI hardware device that 
>>I would like
>>to integrate with UDEV to get UDEV to generate the /dev nodes.
> 
> 
> Is the source of the driver available?
> 
> Kay
> 
> 
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Hi Kay,

Thanks for the response.
Yes, the source code is available, and I have expierience in
writing Linux device drivers, but I have not been able to
find any information on what a device driver needs to do
to get udev to work.
Does it need to override the default set up of sysfs ?

Terry


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Re: Question on how to get custom kernel module to work with udev

[Greg KH]

On Sat, Jun 04, 2005 at 07:00:12AM +0100, Terry Barnaby wrote:
> Yes, the source code is available, and I have expierience in
> writing Linux device drivers, but I have not been able to
> find any information on what a device driver needs to do
> to get udev to work.
> Does it need to override the default set up of sysfs ?

No, you need to provide the major/minor of your device through sysfs.
Examples of how to do this are in the Linux Device Drivers book, third
edition, Chapter 14.  It's online for free if you don't want to buy it
at:
	http://lwn.net/Kernel/LDD3/

If you have further questions after reading that, let us know.

thanks,

greg k-h


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Re: Question on how to get custom kernel module to work with udev

[Greg KH]

On Fri, Jun 03, 2005 at 11:30:26PM -0700, Greg KH wrote:
> On Sat, Jun 04, 2005 at 07:00:12AM +0100, Terry Barnaby wrote:
> > Yes, the source code is available, and I have expierience in
> > writing Linux device drivers, but I have not been able to
> > find any information on what a device driver needs to do
> > to get udev to work.
> > Does it need to override the default set up of sysfs ?
> 
> No, you need to provide the major/minor of your device through sysfs.
> Examples of how to do this are in the Linux Device Drivers book, third
> edition, Chapter 14.

Page 404 is what you want to look at, to be specific.

thanks,

greg k-h


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Re: Question on how to get custom kernel module to work with udev

[Terry Barnaby]

Hi Greg,

Thanks very much for this, this looks exactly the
information I need.

Maybe a link to this information for device driver
writers would be useful on the main udev.html page ?

Cheers

Terry


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Re: Question on how to get custom kernel module to work with udev

[Greg KH]

On Sat, Jun 04, 2005 at 08:06:33AM +0100, Terry Barnaby wrote:
> 
> Maybe a link to this information for device driver
> writers would be useful on the main udev.html page ?

What, don't all device driver writers already have a copy of this book?
:)

Yeah, it's also been described in the archives of this list and lkml a
few times too, but sure if you have a suggested change to the .html
file, I'll consider it.

thanks,

greg k-h


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Re: Question on how to get custom kernel module to work with udev

[Terry Barnaby]

Greg KH wrote:
> On Sat, Jun 04, 2005 at 08:06:33AM +0100, Terry Barnaby wrote:
> 
>>Maybe a link to this information for device driver
>>writers would be useful on the main udev.html page ?
> 
> 
> What, don't all device driver writers already have a copy of this book?
> :)
> 
> Yeah, it's also been described in the archives of this list and lkml a
> few times too, but sure if you have a suggested change to the .html
> file, I'll consider it.
> 
> thanks,
> 
> greg k-h
> 
> 
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All my device driver info and that I could find on the net was
out of date.
A suggested change to the udev.html file is:
In the "Documentation Section" a link to "http://lwn.net/Kernel/LDD3/"
with text: "Udev information for kernel device driver writers is in
the Linux Device Drivers, Third Edition book".

Terry



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