Re: [Qemu-devel] [PATCH V2 4/9] Add tpm_tis driver to build process

[Stefan Berger <stefanb@linux.vnet.ibm.com>]

On 04/05/2011 02:55 PM, Blue Swirl wrote:
> On Tue, Apr 5, 2011 at 9:33 PM, Stefan Berger
> <stefanb@linux.vnet.ibm.com>  wrote:
>> On 04/05/2011 01:45 PM, Blue Swirl wrote:
>>> On Tue, Apr 5, 2011 at 5:08 AM, Stefan Berger
>>> <stefanb@linux.vnet.ibm.com>    wrote:
>>>> On 04/03/2011 05:20 AM, Blue Swirl wrote:
>>>>> On Fri, Apr 1, 2011 at 10:57 PM, Stefan Berger
>>>>> <stefanb@linux.vnet.ibm.com>      wrote:
>>>>>> On 04/01/2011 02:14 PM, Blue Swirl wrote:
>>>>>>
>>>>>> At this point there is no compile test needed since all code is
>>>>>> 'there'.
>>>>>> It's merely adding the front-end,i.e., the TPM TIS emulation to be
>>>>>> compiled.
>>>>> If the basic device (without the tpms-devel library) can be built on
>>>>> any OS, the flag should go to default-configs/*86*-softmmu.mak.
>>>>>
>>>> It can be built on any OS, but it is of no use since the backend
>>>> (libtpms)
>>>> is only available on Linux and we don't support it on another OS. Unless
>>>> someone else wants to port it to other OSes, I'd say that the test for
>>>> Linux
>>>> is useful.
>>>> I'd actually also only compile the TIS if libtpms could be found, and
>>>> terminate with an error message otherwise. I would add this restriction
>>>> only
>>>> in the last patch, so that in patch 4 at least for now the TIS can be
>>>> built.
>>>> Does that sound reasonable?
>>> It should be possible to emulate the device (to some degree) without
>>> relying on backend. See for example the recently committed smart card
>>> device.
>>>
>> In case of a TPM, the specs are huge and translate into multiple 10k lines
>> of code. If there was to be a dummy backend, all it could send back would be
>> error messages...
> Then how about emulating the library instead so that all calls return failure?
That device would be of no use for a user and only serve the purpose of 
test-compiling it if it was for detecting bit rot.
> If a device is built only in special circumstances, it will be more
> prone to bit rot. We have a few such devices though, so it's not so
> big deal.
>
I'll be following the project and there is interest to keep this device 
working.

    Stefan