[PATCH 8/8] ethdev: telemetry convert capability related variable to hex

[Bruce Richardson]

On Thu, Dec 08, 2022 at 11:55:16AM +0100, Morten Brørup wrote:
> +To: Bruce and Stephen might also have opinions on this.
> 
> > From: Huisong Li [mailto:lihuisong at huawei.com]
> > Sent: Thursday, 8 December 2022 09.06
> > 
> > The 'dev_flags', 'rx_offloads', 'tx_offloads' and 'rss_hf' are suitable
> > for hexadecimal display.
> > 
> > Like:
> >  -->old display by input /ethdev/info,0
> >       "dev_flags": 3,
> >       "rx_offloads": 524288,
> >       "tx_offloads": 65536,
> >       "ethdev_rss_hf": 9100
> > 
> >  --> now display
> >      "dev_flags": "0x3",
> >      "rx_offloads": "0x80000",
> >      "tx_offloads": "0x10000",
> >      "ethdev_rss_hf": "0x238c"
> 
> This is certainly good for human consumption, but perhaps not for machine consumption (where a number type is more appropriate than a string type).
> 
> Unfortunately, the JSON format [RFC7159] does not allow hexadecimal numbers, so hexadecimal values (if supported) have to be passed as strings.
> 
> [RFC7159]: https://www.rfc-editor.org/rfc/rfc7159
> 
> This leaves us with the key question:
> 
> Do we want to provide integer values like these as hexadecimal encoded strings?
> 
> If we do, then the telemetry library should provide the functions to do it, rather than doing it here (and everywhere else, where relevant).
> 

My initial thought was "no, we shouldn't do that, and just treat numbers as
numbers", and let the end-user display software worry about formatting it
correctly. However, I have since changed my mind, in that:

* Although these are numbers, they are not used for computation, or
  comparison
* Having them as strings makes them more useful for "dumb-client"
  connections, like that of the telemetry script in DPDK
* If display software is aware of the significance of these values and does
  want to do additional parsing of the flags, e.g. to map them to named
  flags, converting a string back to a number is not a difficult task.
* These values are not changing between polls, so any convertion/processing
  of the flags to be done before display only needs to be done once (except
  in very rare circumstances of a port reconfiguration)

So overall, I would tend to agree with your proposal, in that it would be
good for telemetry lib to provide this functionality.

Regards,
/Bruce