[dpdk-dev] [PATCH 4/4] pmd_hw_support.py: Add tool to query binaries for hw support information

[Panu Matilainen]

On 05/16/2016 11:41 PM, Neil Horman wrote:
> This tool searches for the primer sting PMD_DRIVER_INFO= in any ELF binary,
> and, if found parses the remainder of the string as a json encoded string,
> outputting the results in either a human readable or raw, script parseable
> format
>
> Signed-off-by: Neil Horman <nhorman at tuxdriver.com>
> CC: Bruce Richardson <bruce.richardson at intel.com>
> CC: Thomas Monjalon <thomas.monjalon at 6wind.com>
> CC: Stephen Hemminger <stephen at networkplumber.org>
> CC: Panu Matilainen <pmatilai at redhat.com>
> ---
>  tools/pmd_hw_support.py | 174 ++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 174 insertions(+)
>  create mode 100755 tools/pmd_hw_support.py
>
> diff --git a/tools/pmd_hw_support.py b/tools/pmd_hw_support.py
> new file mode 100755
> index 0000000..0669aca
> --- /dev/null
> +++ b/tools/pmd_hw_support.py
> @@ -0,0 +1,174 @@
> +#!/usr/bin/python3

I think this should use /usr/bin/python to be consistent with the other 
python scripts, and like the others work with python 2 and 3. I only 
tested it with python2 after changing this and it seemed to work fine so 
the compatibility side should be fine as-is.

On the whole, AFAICT the patch series does what it promises, and works 
for both static and shared linkage. Using JSON formatted strings in an 
ELF section is a sound working technical solution for the storage of the 
data. But the difference between the two cases makes me wonder about 
this all...

For static library build, you'd query the application executable, eg 
testpmd, to get the data out. For a shared library build, that method 
gives absolutely nothing because the data is scattered around in 
individual libraries which might be just about wherever, and you need to 
somehow discover the location + correct library files to be able to 
query that. For the shared case, perhaps the script could be taught to 
walk files in CONFIG_RTE_EAL_PMD_PATH to give in-the-ballpark 
correct/identical results when querying the executable as with static 
builds. If identical operation between static and shared versions is a 
requirement (without running the app in question) then query through the 
executable itself is practically the only option. Unless some kind of 
(auto-generated) external config file system ala kernel depmod / 
modules.dep etc is brought into the picture.

For shared library configurations, having the data in the individual 
pmds is valuable as one could for example have rpm autogenerate provides 
from the data to ease/automate installation (in case of split packaging 
and/or 3rd party drivers). And no doubt other interesting possibilities. 
With static builds that kind of thing is not possible.

Calling up on the list of requirements from 
http://dpdk.org/ml/archives/dev/2016-May/038324.html, I see a pile of 
technical requirements but perhaps we should stop for a moment to think 
about the use-cases first?

To name some from the top of my head:
- user wants to know whether the hardware on the system is supported
- user wants to know which package(s) need to be installed to support 
the system hardware
- user wants to list all supported hardware before going shopping
- [what else?]

...and then think how these things would look like from the user 
perspective, in the light of the two quite dramatically differing cases 
of static vs shared linkage.

P.S. Sorry for being late to this party, I'm having some health issues 
so my level of participation is a bit on-and-off at the moment.

	- Panu -