RE: [EXTERNAL] [PATCH v2 1/2] crypto: fix build issues on unsetting crypto callbacks macro

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

> From: Akhil Goyal [mailto:gakhil@marvell.com]
> Sent: Thursday, 30 May 2024 13.47
> 
> > > > #if may not be needed in application.
> > > > Test should be skipped if API is not available/supported.
> > > >
> > It's needed otherwise application developer has to check the implementation
> for
> > supported/not supported or else
> > run the application to get to know whether api is supported or not.
> >
> 
> Application is always required to check the return value
> or else it will miss the other errors that the API can return.
> 
> > > > > diff --git a/lib/cryptodev/rte_cryptodev.c
> > > > > b/lib/cryptodev/rte_cryptodev.c index 886eb7a..2e0890f 100644
> > > > > --- a/lib/cryptodev/rte_cryptodev.c
> > > > > +++ b/lib/cryptodev/rte_cryptodev.c
> > > > > @@ -628,6 +628,7 @@
> > > rte_cryptodev_asym_xform_capability_check_hash(
> > > > >  	return ret;
> > > > >  }
> > > > >
> > > > > +#if RTE_CRYPTO_CALLBACKS
> > > > >  /* spinlock for crypto device enq callbacks */  static
> > > > > rte_spinlock_t rte_cryptodev_callback_lock =
> > > > RTE_SPINLOCK_INITIALIZER;
> > > > >
> > > > > @@ -744,6 +745,7 @@ cryptodev_cb_init(struct rte_cryptodev *dev)
> > > > >  	cryptodev_cb_cleanup(dev);
> > > > >  	return -ENOMEM;
> > > > >  }
> > > > > +#endif /* RTE_CRYPTO_CALLBACKS */
> > > >
> > > >
> > > > > @@ -1485,6 +1491,7 @@ rte_cryptodev_queue_pair_setup(uint8_t
> > > dev_id,
> > > > > uint16_t queue_pair_id,
> > > > >  			socket_id);
> > > > >  }
> > > > >
> > > > > +#if RTE_CRYPTO_CALLBACKS
> > > > >  struct rte_cryptodev_cb *
> > > > >  rte_cryptodev_add_enq_callback(uint8_t dev_id,
> > > > >  			       uint16_t qp_id,
> > > > > @@ -1763,6 +1770,7 @@ rte_cryptodev_remove_deq_callback(uint8_t
> > > dev_id,
> > > > >  	rte_spinlock_unlock(&rte_cryptodev_callback_lock);
> > > > >  	return ret;
> > > > >  }
> > > > > +#endif /* RTE_CRYPTO_CALLBACKS */
> > > >
> > > > There is an issue here.
> > > > The APIs are visible in .h file and are available for application to
> use.
> > > > But the API implementation is compiled out.
> > > > Rather, you should add a return ENOTSUP from the beginning of the APIs
> > > > if RTE_CRYPTO_CALLBACKS  is enabled.
> > > > With this approach application will not need to put #if in its code.
> > API declarations wrapped under the macro changes in next patch.
> 
> No, that is not the correct way. Application should check the return value.
> And we cannot force it to add ifdefs.

Agree; the function must always be present in DPDK, but fail if built without callbacks.

The ethdev function to add a callback does this [1]:

const struct rte_eth_rxtx_callback *
rte_eth_add_rx_callback(uint16_t port_id, uint16_t queue_id,
		rte_rx_callback_fn fn, void *user_param)
{
#ifndef RTE_ETHDEV_RXTX_CALLBACKS
	rte_errno = ENOTSUP;
	return NULL;
#endif
	struct rte_eth_dev *dev;
	[...]


[1]: https://elixir.bootlin.com/dpdk/v24.03/source/lib/ethdev/rte_ethdev.c#L5729