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

-----Original Message-----
From: Fredrik A Lindgren <redacted>
Sent: Monday, February 1, 2021 10:02 AM
To: Van Haaren, Harry <redacted>; dev@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 <redacted>
Sent: den 1 februari 2021 10:44
To: Fredrik A Lindgren <redacted>; dev@dpdk.org
Subject: RE: Question: typedef of eventdev_info_get_t bug?

quoted

-----Original Message-----
From: dev <redacted> On Behalf Of Fredrik A Lindgren
Sent: Monday, February 1, 2021 9:22 AM
To: dev@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.

quoted

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.

*/

quoted

...

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().

quoted

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.

quoted

Br,
Fredrik

Regards, -Harry