Re: Fwd: [PATCH] [-mm] ACPI: export ACPI events via netlink

[Zhang Rui <rui.zhang@intel.com>]

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Hi, Jamal,

Now the genl utility can find the acpi event genetlink family.
And a simple user space demo is finished for handling acpi event.
I really appreciate your help. :)

I think the patch which exposes ACPI events via netlink is ok.
But I still have some problems on
how to listen to specified genetlink family in user space?

I can get the dynamic id for "acpi_event" genl family.
But I don't know how to use this to receive messages from
specified genl family.
It seems that "#genl ctrl monitor" has something to do with this,
IMO, rtnl_open_byproto(&rth, nl_mgrp(GENL_ID_CTRL), NETLINK_GENERIC) is
used to receive messages from the nlctrl(controller) only, but
unfortunately it never works for me. :(

Any suggestions? What interfaces should I use? Or where can I find some
example code?

Attachment is the simple user space demo I made.
It receives all the broadcasted genetlink messages and only parses the
ones sent by "acpi_event" genl family.


Thanks,
Rui

On Sun, 2007-05-27 at 09:34 -0400, jamal wrote: 
> On 5/27/07, Zhang Rui <rui.zhang@intel.com> wrote:
> >
> > I need to write a user application to test my patch.
> > Netlink messages can be sent/received using the standard socket API.
> 
> sure.
> 
> > But how to receive Genetlink messages from specified genetlink family?
> > There is no socket ACPI with such a parameter, right?
> 
> Each module has a unique identifier that it receives dynamically on
>  insertion at the kernel.
> 
> > Do I have to receive all the genetlink messages first?
> 
>  No, just the ones for your dynamic id. Try what i described first for
>  kernel side on the earlier email. I will repeat it here for clarity.
> Then look at genl code and if you have questions i can
>  help.
> Note: You need to discover your dynamic id (the iproute2/genl code has a stub
> example code)
>  As i told you in the earlier email, in your development:
>  - start first by just writting your kernel side.
>  - Then use the genl utility - which is part of iproute2 to see if the
>  kernel side is "discoverable".
> 
>  E.g if i wanted to "discover" currently loaded modules on my laptop, i
>  would do this:
> 
>  ---------------
>  hadi@lilsol:~$ genl ctrl ls
> 
>  Name: nlctrl
>          ID: 0x10  Version: 0x2  header size: 0  max attribs: 6
>          commands supported:
>                  #1:  ID-0x3  flags-0xe
> 
> 
>  Name: nl80211
>          ID: 0x11  Version: 0x1  header size: 0  max attribs: 22
>          commands supported:
>                  #1:  ID-0x1  flags-0xa
>                  #2:  ID-0x6  flags-0xa
>                  #3:  ID-0x8  flags-0xa
>                  #4:  ID-0x3  flags-0xb
>                  #5:  ID-0x4  flags-0xb
>                  #6:  ID-0x5  flags-0xb
>                  #7:  ID-0xa  flags-0xb
>                  #8:  ID-0xb  flags-0xa
>                  #9:  ID-0xf  flags-0xb
>                  #10:  ID-0x10  flags-0xa
>                  #11:  ID-0x12  flags-0xb
>                  #12:  ID-0x13  flags-0xa
>                  #13:  ID-0x15  flags-0xa
>                  #14:  ID-0x19  flags-0xb
>                  #15:  ID-0x17  flags-0xb
>                  #16:  ID-0x18  flags-0xb
>                  #17:  ID-0x1a  flags-0xb
>                  #18:  ID-0x1b  flags-0xa
>                  #19:  ID-0xd  flags-0xb
> 
> 
>  Name: TASKSTATS
>          ID: 0x12  Version: 0x1  header size: 0  max attribs: 4
>          commands supported:
>                  #1:  ID-0x1  flags-0xa
>  ---------------------------
> 
>  As you can see, i can see from user space the name of the kernel end
>  point, its numeric id, what version it is running (so i can make sure
>  user space is compatible), what extra header it may have, what the
>  maximum number of attributes it can take. The last thing that gets
>  listed is the commands, and flags for those commands.
> 
>  Lets load tipc kernel module and repeat...
> 
>  -----------
> 
>  hadi@lilsol:~$ sudo modprobe tipc
>  Name: nlctrl
>          ID: 0x10  Version: 0x2  header size: 0  max attribs: 6
>          commands supported:
>                  #1:  ID-0x3  flags-0xe
> 
>  ....
>  [same as before]
>  ....
> 
>  Name: TIPC
>          ID: 0x13  Version: 0x1  header size: 8  max attribs: 0
>          commands supported:
>                  #1:  ID-0x1  flags-0x2
> 
>  ===============
> 
> > It would be great if there are any examples on user space communication.
> 
> 
> 
> Bug Thomas - he has written some simple example. I also have some but i
>  changed laptops and i have to go and dig it up for you.
>  I do have plans for making this easier for people - but havent had time.
>  If there is persistence - or someone out there wants to be a hero email
>  me privately and i will explain it.
> 
> > Or should I use libnl library instead?
> 
> Why am i answering all these questions if you are fine with using libnl?
> Last time you said you couldnt use a library, no?
> 
> cheers,
> jamal
> 
> 
> > Thanks,
> > Rui.
> >

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