RE: [PATCH v2 1/2] ethdev: remove unnecessary type conversion

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Tuesday, 27 May 2025 17.07
> 
> On Mon, 12 May 2025 20:37:19 +0530
> <skori@marvell.com> wrote:
> 
> >  /**@{@name Rx hardware descriptor states
> > diff --git a/lib/ethdev/rte_ethdev_core.h
> b/lib/ethdev/rte_ethdev_core.h
> > index e55fb42996..4ffae4921a 100644
> > --- a/lib/ethdev/rte_ethdev_core.h
> > +++ b/lib/ethdev/rte_ethdev_core.h
> > @@ -45,7 +45,7 @@ typedef uint16_t (*eth_tx_prep_t)(void *txq,
> >
> >
> >  /** @internal Get number of used descriptors on a receive queue. */
> > -typedef uint32_t (*eth_rx_queue_count_t)(void *rxq);
> > +typedef int (*eth_rx_queue_count_t)(void *rxq);
> >
> >  /** @internal Check the status of a Rx descriptor */
> >  typedef int (*eth_rx_descriptor_status_t)(void *rxq, uint16_t
> offset);
> 
> 
> This gets reported as ABI breakage. The change will have to wait until
> next LTS (25.11)

The return type was weird (wrong) to begin with.
When used, it gets cast to int:
https://elixir.bootlin.com/dpdk/v25.03/source/lib/ethdev/rte_ethdev.h#L6404

You are right that it formally changes the ABI, and we should go through the LTS motions.
But, for this change, I'd favor an exception.

PS: As a consequence of this change, a patch to update the return type of the callback in all the ethdev drivers should be provided.

> 
> 
>   [C] 'rte_eth_fp_ops rte_eth_fp_ops[32]' was changed at
> rte_ethdev.c:47:1:
>     type of variable changed:
>       array element type 'struct rte_eth_fp_ops' changed:
>         type size hasn't changed
>         1 data member change:
>           type of 'eth_rx_queue_count_t rx_queue_count' changed:
>             underlying type 'uint32_t (*)(void*)' changed:
>               in pointed to type 'function type uint32_t (void*)':
>                 return type changed:
>                   entity changed from 'typedef uint32_t' to 'int'
>                   type size hasn't changed
>       type size hasn't changed