how to make xenbus do .probe?

how to make xenbus do .probe?

[Jian Wang]

Hi,
Can anyone please tell me how to get  ".probe" function in "struct
xenbus_driver" called?
I want to do one simple test of  event channel communication between
peer modules of
domU and dom0.
I wrote one backend and one frontend driver (I tried registered as
misc/blk/input device) where I put in all my xenbus routines, but
cannot get .probe called after  insmod my module, I have put
one week's time to try to find the answer,  failed.

Thanks a lot!
-Jian

Re: how to make xenbus do .probe?

[Jian Wang]

I know it is a naive question. But can anyone please give me one hand on this?

I tried the example of
"http://wiki.xensource.com/xenwiki/XenIntro#head-d210a9b066af7165219af8f0652a12137245a123"
 does not work.

Thanks a lot!
-Jian

On 2/28/07, Jian Wang <jeans.wang@gmail.com> wrote:
> Hi,
> Can anyone please tell me how to get  ".probe" function in "struct
> xenbus_driver" called?
> I want to do one simple test of  event channel communication between
> peer modules of
> domU and dom0.
> I wrote one backend and one frontend driver (I tried registered as
> misc/blk/input device) where I put in all my xenbus routines, but
> cannot get .probe called after  insmod my module, I have put
> one week's time to try to find the answer,  failed.
>
> Thanks a lot!
> -Jian
>

Re: how to make xenbus do .probe?

[Jian Wang]

In the Xenintro, before  "triggering of probe() in a backend driver"
example,  it says:

"Note: this example worked in the past, but with the release of xen
3.0 it stopped to work. We are working on fixing it."

Anyone knows whom could  I get help from? This example is really important for
beginners like me to start with.
-Jian


On 3/5/07, Jian Wang <jeans.wang@gmail.com> wrote:
> I know it is a naive question. But can anyone please give me one hand on this?
>
> I tried the example of
> "http://wiki.xensource.com/xenwiki/XenIntro#head-d210a9b066af7165219af8f0652a12137245a123"
>  does not work.
>
> Thanks a lot!
> -Jian
>
> On 2/28/07, Jian Wang <jeans.wang@gmail.com> wrote:
> > Hi,
> > Can anyone please tell me how to get  ".probe" function in "struct
> > xenbus_driver" called?
> > I want to do one simple test of  event channel communication between
> > peer modules of
> > domU and dom0.
> > I wrote one backend and one frontend driver (I tried registered as
> > misc/blk/input device) where I put in all my xenbus routines, but
> > cannot get .probe called after  insmod my module, I have put
> > one week's time to try to find the answer,  failed.
> >
> > Thanks a lot!
> > -Jian
> >
>

Re: how to make xenbus do .probe?

[Ryan Riley]

Yeah, the wiki page you refer to in a later message is incorrect, but I 
think that the major thing wrong with it is the xenstore-write commands. 
(At the moment I don't have time to check whether the skeleton driver 
code is correct, and I can't remember if I had to tweak it when I went 
through what you're going through.)

Here's 4 xenstore-write commands that should get a probe out of the device:

xenstore-write /local/domain/5/device/mydevice/0/state 1

xenstore-write /local/domain/0/backend/mydevice/5/0/frontend-id 5

xenstore-write /local/domain/0/backend/mydevice/5/0/frontend 
/local/domain/5/device/mydevice/0

xenstore-write /local/domain/0/backend/mydevice/5/0/state 1

Quick note: That will only work once per boot, because once the driver
is probed with frontend-id 5 the xenbus code seems to be smart enough to
not do it again.  If you need to make another probe happen during the
same boot, just increment the 5 all around.  I hope this helps.

Thanks
Ryan

Jian Wang <jeans.wang@gmail.com> wrote:
>    Hi,
>    Can anyone please tell me how to get  ".probe" function in "struct
>    xenbus_driver" called?
>    I want to do one simple test of  event channel communication between
>    peer modules of
>    domU and dom0.
>    I wrote one backend and one frontend driver (I tried registered as
>    misc/blk/input device) where I put in all my xenbus routines, but
>    cannot get .probe called after  insmod my module, I have put
>    one week's time to try to find the answer,  failed.
>
>    Thanks a lot!
>    -Jian
>
>     

Re: how to make xenbus do .probe?

[Ryan Riley]

[-- Attachment #1: Type: text/plain, Size: 2628 bytes --]

Attached you'll find a simple bash script illustrating how to get both 
the backend and frontend of the skeleton driver to fire.

Here's how to use it:
-Startup a Xen guest that contains your frontend driver, and be sure 
dom0 contains the backend driver.
-Figure out the frontend-id for the guest.  (I only have one guest so, 
the frontend-id is the number on the first line of `xenstore-ls 
/local/domain/0/backend/vbd`).  Let's pretend that number is 3.
-Run the script as so:  ./probetest.sh mydevice 3

That should fire both probes.

The only tricky things about the script are writing the states in the 
right order and changing the permissions of one of the xenstore keys.

Thanks
Ryan

Jian Wang wrote:
> It really works for backend!!
> Thanks a lot.
> But seems frontend .probe still not got called.
> Could you tell me how to adjust the parameter to make the frontend do 
> probe?
> -Jian
>
>
> On 3/6/07, Ryan Riley <rileyrd@purdue.edu> wrote:
>> Yeah, the wiki page you refer to in a later message is incorrect, but I
>> think that the major thing wrong with it is the xenstore-write commands.
>> (At the moment I don't have time to check whether the skeleton driver
>> code is correct, and I can't remember if I had to tweak it when I went
>> through what you're going through.)
>>
>> Here's 4 xenstore-write commands that should get a probe out of the 
>> device:
>>
>> xenstore-write /local/domain/5/device/mydevice/0/state 1
>>
>> xenstore-write /local/domain/0/backend/mydevice/5/0/frontend-id 5
>>
>> xenstore-write /local/domain/0/backend/mydevice/5/0/frontend
>> /local/domain/5/device/mydevice/0
>>
>> xenstore-write /local/domain/0/backend/mydevice/5/0/state 1
>>
>> Quick note: That will only work once per boot, because once the driver
>> is probed with frontend-id 5 the xenbus code seems to be smart enough to
>> not do it again.  If you need to make another probe happen during the
>> same boot, just increment the 5 all around.  I hope this helps.
>>
>> Thanks
>> Ryan
>>
>> Jian Wang <jeans.wang@gmail.com> wrote:
>> >    Hi,
>> >    Can anyone please tell me how to get  ".probe" function in "struct
>> >    xenbus_driver" called?
>> >    I want to do one simple test of  event channel communication 
>> between
>> >    peer modules of
>> >    domU and dom0.
>> >    I wrote one backend and one frontend driver (I tried registered as
>> >    misc/blk/input device) where I put in all my xenbus routines, but
>> >    cannot get .probe called after  insmod my module, I have put
>> >    one week's time to try to find the answer,  failed.
>> >
>> >    Thanks a lot!
>> >    -Jian
>> >
>> >
>>
>>
>>


[-- Attachment #2: probetest.sh --]
[-- Type: text/plain, Size: 995 bytes --]

#!/bin/bash

if [ $# != 2 ]
then
	echo "Usage: $0 <device name> <frontend-id>"
else
	# Write backend information into the location the frontend will look 
	# for it.
	xenstore-write /local/domain/${2}/device/${1}/0/backend-id 0
	xenstore-write /local/domain/${2}/device/${1}/0/backend \
		       /local/domain/0/backend/${1}/${2}/0

	# Write frontend information into the location the backend will look 
	# for it.
	xenstore-write /local/domain/0/backend/${1}/${2}/0/frontend-id ${2}
	xenstore-write /local/domain/0/backend/${1}/${2}/0/frontend \
		       /local/domain/${2}/device/${1}/0

	# Set the permissions on the backend so that the frontend can 
	# actually read it.
	xenstore-chmod /local/domain/0/backend/${1}/${2}/0 r

	# Write the states.  Note that the backend state must be written 
	# last because it requires a valid frontend state to already be 
	# written.
	xenstore-write /local/domain/${2}/device/${1}/0/state 1
	xenstore-write /local/domain/0/backend/${1}/${2}/0/state 1
fi

[-- Attachment #3: Type: text/plain, Size: 138 bytes --]

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