[dpdk-dev] Question: typedef of eventdev_info_get_t bug?

[Van Haaren, Harry]

> -----Original Message-----
> From: Fredrik A Lindgren <Fredrik.a.Lindgren at tietoevry.com>
> Sent: Monday, February 1, 2021 10:02 AM
> To: Van Haaren, Harry <harry.van.haaren at intel.com>; dev at dpdk.org
> Subject: RE: Question: typedef of eventdev_info_get_t bug?
> 
> Hi Harry,
> 
> You are correct, multiple structs with dev_infos_get defined in them caused me to
> jump to wrong implementation.

No problem.

> Still a bit "wrong" that comment for eventdev_info_get_t for event setup states
> returns 0 on success.

Agreed, a patch would be welcome to remove the "@return" bit of the docs.
I can send it if you say you're not planning to, its a small/easy patch.

> Using older version of
> https://github.com/Xilinx/dma_ip_drivers/tree/master/QDMA/DPDK targeting dpdk-
> 19.11 for a corporate internal project as such can't give much details.
> That version had a issue with no return statements in the infos_get function which
> was causing me issues.

Sounds like you've root-caused and know of a solution.

> Br,
> Fredrik

Regards, -Harry

> -----Original Message-----
> From: Van Haaren, Harry <harry.van.haaren at intel.com>
> Sent: den 1 februari 2021 10:44
> To: Fredrik A Lindgren <Fredrik.a.Lindgren at tieto.com>; dev at dpdk.org
> Subject: RE: Question: typedef of eventdev_info_get_t bug?
> 
> > -----Original Message-----
> > From: dev <dev-bounces at dpdk.org> On Behalf Of Fredrik A Lindgren
> > Sent: Monday, February 1, 2021 9:22 AM
> > To: dev at dpdk.org
> > Subject: [dpdk-dev] Question: typedef of eventdev_info_get_t bug?
> >
> > While debugging a driver I was looking at the code and realized that
> > eventdev_info_get_t typedef is defined with void return value but
> > documentation for it says it should return 0
> 
> Hi Fredrik,
> 
> Be aware that your snippets of code below is mixing Event-dev and Eth-dev.
> This is likely the cause of confusion.
> 
> 
> > lib/librte_eventdev/eventdev_pmd.h:
> >
> > ...
> > * @return
> > *   Returns 0 on success
> > */
> > typedef void (*eventdev_info_get_t)(struct rte_eventdev *dev,
> >                                                           struct
> > rte_event_dev_info *dev_info); ...
> > struct rte_eventdev_ops {
> >                              eventdev_info_get_t dev_infos_get;              /**< Get device info.
> */
> > ...
> >
> > While return value from it is used in lib/librte_ethdev/rte_ethdev.c:
> >
> > int
> > rte_eth_dev_info_get(uint16_t port_id, struct rte_eth_dev_info
> > *dev_info) ...
> >    diag = (*dev->dev_ops->dev_infos_get)(dev, dev_info);
> >    if (diag != 0) {
> > ...
> 
> At the Eventdev layer, info_get() can return int (particularly 0 on success, or -ERROR
> values).
> At the Eventdev PMD layer, info_get() has a return void (the PMD cannot indicate
> failure on providing its info)
> 
> Hence, the info_get() typedef (for the PMD) is void, but the Eventdev layer itself
> checks some dev_id values etc, and can return -EINVAL or -ENOTSUP in case the
> PMD doesn't support info_get().
> 
> 
> > Driver I'm debugging doesn't have any return statement in it's
> > dev_infos_get function which seems to cause it to have "result" of
> > last operation done in that function as return value.
> > Though this behavior may be compiler specific but it should probably
> > be clarified and updated (change prototype of stop using return value) to avoid
> issue with it.
> 
> Perhaps provide some more detail on Eventdev/Ethdev that you're debugging a
> driver on, provide some links to specific parts of the code? It seems like (from
> Eventdev anyway) its meant to work this way.
> 
> > Br,
> > Fredrik
> 
> Regards, -Harry