Re: [dpdk-dev] [PATCH v2 2/4] ethdev: add siblings iterators

[Thomas Monjalon <thomas@monjalon.net>]

19/03/2019 16:47, Ferruh Yigit:
> On 2/20/2019 10:10 PM, Thomas Monjalon wrote:
> > If multiple ports share the same hardware device (rte_device),
> > they are siblings and can be found thanks to the new functions
> > and loop macros.
> > One iterator takes a port id as reference,
> > while the other one directly refers to the parent device.
> > 
> > The ownership is not checked because siblings may have
> > different owners.
> > 
> > Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> > ---
> >  lib/librte_ethdev/rte_ethdev.c           | 20 +++++++++++
> >  lib/librte_ethdev/rte_ethdev.h           | 46 ++++++++++++++++++++++++
> >  lib/librte_ethdev/rte_ethdev_version.map |  2 ++
> >  3 files changed, 68 insertions(+)
> > 
> > diff --git a/lib/librte_ethdev/rte_ethdev.c b/lib/librte_ethdev/rte_ethdev.c
> > index b3b2fb1dba..42154787f8 100644
> > --- a/lib/librte_ethdev/rte_ethdev.c
> > +++ b/lib/librte_ethdev/rte_ethdev.c
> > @@ -340,6 +340,26 @@ rte_eth_find_next(uint16_t port_id)
> >  	return port_id;
> >  }
> >  
> > +uint16_t __rte_experimental
> 
> Do we need _rte_experimental on function definitions? I guess only in .h file,
> function declaration is enough.

Yes we need them both in .h and .c files.

> > +rte_eth_find_next_of(uint16_t port_id, const struct rte_device *parent)
> 
> Out of curiosity, what '_of' refers to?

It means "next port of parent".
Is there a better word than "of"?

> > +{
> > +	while (port_id < RTE_MAX_ETHPORTS &&
> > +			rte_eth_devices[port_id].state == RTE_ETH_DEV_UNUSED &&
> > +			rte_eth_devices[port_id].device != parent)
> > +		port_id++;
> 
> Is this logic correct, or am I missing something.
> When port status is ATTACHED, check will return false and exit from loop without
> checking if the 'device' is same.

Oops, I think you are right.

> +1 to Gaetan's suggestion to use 'rte_eth_find_next()', which moves status
> concern to that function.

OK, will change.

> > +
> > +	if (port_id >= RTE_MAX_ETHPORTS)
> > +		return RTE_MAX_ETHPORTS;
> > +
> > +	return port_id;
> > +}
> > +
> > +uint16_t __rte_experimental
> > +rte_eth_find_next_sibling(uint16_t port_id, uint16_t ref)
> 
> I think better to say 'ref_port_id' to clarify what we expect here is a port_id

OK

> > +{
> > +	return rte_eth_find_next_of(port_id, rte_eth_devices[ref].device);
> 
> This is a public API, shouldn't we check if 'ref' if valid port_id value, before
> accessing the '.device' field?

I'm not a fan of extra checks, but yes we may add one.

> > --- a/lib/librte_ethdev/rte_ethdev.h
> > +++ b/lib/librte_ethdev/rte_ethdev.h
> > +/**
> > + * Iterates over ethdev ports of a specified device.
> > + *
> > + * @param port_id_start
> > + *   The id of the next possible valid port.
> > + * @param parent
> > + *   The generic device behind the ports to iterate.
> > + * @return
> > + *   Next port id of the device, RTE_MAX_ETHPORTS if there is none.
> 
> Can return 'port_id_start', right? Should it be documented as it is done in
> below 'next_sibling' one?

Yes, OK.

> > + */
> > +__rte_experimental
> > +uint16_t rte_eth_find_next_of(uint16_t port_id_start,
> > +		const struct rte_device *parent);
> > +
> > +/**
> > + * Macro to iterate over all ethdev ports sharing the same rte_device
> > + * as the specified port.
> 
> 'specified port'? No port specified, a device pointer is specified.

Right, looks like a wrong a copy/paste.

> > + * Note: the specified port is part of the loop iterations.
> > + */
> 
> Does it make sense to clarify what 'p' is and what 'parent' is as we do in
> function doxygen comments? Since these are macros, harder to grasp the types, I
> think better to describe more in macro documentation.

Absolutely, yes. I thought I did it.

> > +#define RTE_ETH_FOREACH_DEV_OF(p, parent) \
> > +	for (p = rte_eth_find_next_of(0, parent); \
> > +		p < RTE_MAX_ETHPORTS; \
> > +		p = rte_eth_find_next_of(p + 1, parent))
> > +
> > +/**
> > + * Iterates over sibling ethdev ports (i.e. sharing the same rte_device).
> > + *
> > + * @param port_id_start
> > + *   The id of the next possible valid sibling port.
> > + * @param ref
> > + *   The id of a reference port to compare rte_device with.
> > + * @return
> > + *   Next sibling port id (or ref itself), RTE_MAX_ETHPORTS if there is none.
> > + */
> > +__rte_experimental
> > +uint16_t rte_eth_find_next_sibling(uint16_t port_id_start, uint16_t ref);
> > +
> > +/**
> > + * Macro to iterate over all ethdev ports sharing the same rte_device
> > + * as the specified port.
> > + * Note: the specified port is part of the loop iterations.
> > + */
> > +#define RTE_ETH_FOREACH_DEV_SIBLING(p, ref) \
> > +	for (p = rte_eth_find_next_sibling(0, ref); \
> > +		p < RTE_MAX_ETHPORTS; \
> > +		p = rte_eth_find_next_sibling(p + 1, ref))

Thanks for the complete review Ferruh.