[Buildroot] mdev

[Buildroot] mdev

[Marcel]

Hi,

I'm trying to create a couple of device nodes in /dev and somehow doing this 
manually seems not preferred so I'm trying to do this via mdev. 

My first question is whether I'm on the right track by using mdev?

I tried mdev but I can't make it work. Probably this is because I have 
something wrong in either the startup code , the mdev.conf file or whatever. 
Second I wonder how mdev works because I think it needs MAKEDEV or something 
else) which I may be missing and can't find in my buildroot. mknod is on my 
system though.
mdev -s starts and returns after a second or so, I see no errors and no other 
feedback.

I am looking for an example that works with spidev. My guess is that the entry 
in mdev.conf should be something like :

spidev 0:153 0660

Would my kernel need hotplug enabled ? (I guess it does).

I'm using a 2.6.33 kernel with a sam9g45 Atmel processor if that matters.

Best regards,
Marcel

[Buildroot] mdev

[Peter Korsgaard]

>>>>> "Marcel" == Marcel  <korgull@home.nl> writes:

 Marcel> Hi,

 Marcel> I'm trying to create a couple of device nodes in /dev and
 Marcel> somehow doing this manually seems not preferred so I'm trying
 Marcel> to do this via mdev.

 Marcel> My first question is whether I'm on the right track by using mdev?

Yes, that's certainly an OK approach. For an even easier setup have a
look at devtmpfs in the kernel.

 Marcel> I tried mdev but I can't make it work. Probably this is because
 Marcel> I have something wrong in either the startup code , the
 Marcel> mdev.conf file or whatever.  Second I wonder how mdev works
 Marcel> because I think it needs MAKEDEV or something else) which I may
 Marcel> be missing and can't find in my buildroot. mknod is on my
 Marcel> system though.  mdev -s starts and returns after a second or
 Marcel> so, I see no errors and no other feedback.

Ok, good. To generate device nodes at runtime you then need tell the
kernel to use mdev as the hotplug agent. See
target/generic/target_busybox_skeleton/etc/inittab for an example of a
working setup.

 Marcel> I am looking for an example that works with spidev. My guess is
 Marcel> that the entry in mdev.conf should be something like :

 Marcel> spidev 0:153 0660

In general you only need entries in mdev.conf if you need special
handling (non-standard permissions or scripts executed).

 Marcel> Would my kernel need hotplug enabled ? (I guess it does).

Yes.

-- 
Bye, Peter Korsgaard

[Buildroot] mdev

[Marcel]

Hi Peter,

Thanks for your reply.  I checked out devtmpfs and will try that. It looks 
promising.

For some reason assigning a fixed major to my devices stopped working. I still 
used this with the 2.6.28 kernel but now with the 2.6.33 it just won't work.
Perhaps I missed something to why this doesn't work.

Best regards,
Marcel


> >>>>> "Marcel" == Marcel  <korgull@home.nl> writes:
>  Marcel> Hi,
> 
>  Marcel> I'm trying to create a couple of device nodes in /dev and
>  Marcel> somehow doing this manually seems not preferred so I'm trying
>  Marcel> to do this via mdev.
> 
>  Marcel> My first question is whether I'm on the right track by using mdev?
> 
> Yes, that's certainly an OK approach. For an even easier setup have a
> look at devtmpfs in the kernel.
> 
>  Marcel> I tried mdev but I can't make it work. Probably this is because
>  Marcel> I have something wrong in either the startup code , the
>  Marcel> mdev.conf file or whatever.  Second I wonder how mdev works
>  Marcel> because I think it needs MAKEDEV or something else) which I may
>  Marcel> be missing and can't find in my buildroot. mknod is on my
>  Marcel> system though.  mdev -s starts and returns after a second or
>  Marcel> so, I see no errors and no other feedback.
> 
> Ok, good. To generate device nodes at runtime you then need tell the
> kernel to use mdev as the hotplug agent. See
> target/generic/target_busybox_skeleton/etc/inittab for an example of a
> working setup.
> 
>  Marcel> I am looking for an example that works with spidev. My guess is
>  Marcel> that the entry in mdev.conf should be something like :
> 
>  Marcel> spidev 0:153 0660
> 
> In general you only need entries in mdev.conf if you need special
> handling (non-standard permissions or scripts executed).
> 
>  Marcel> Would my kernel need hotplug enabled ? (I guess it does).
> 
> Yes.