Re: [dpdk-dev] [PATCH] net/e1000: do not error out if rx_drop_en is set

[Luca Boccassi <bluca@debian.org>]

On Mon, 2018-10-08 at 08:43 +0000, Zhao1, Wei wrote:
> Hi,  Luca Boccassi
> 
> > -----Original Message-----
> > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Luca Boccassi
> > Sent: Saturday, July 28, 2018 1:26 AM
> > To: dev@dpdk.org
> > Cc: Lu, Wenzhuo <wenzhuo.lu@intel.com>; Luca Boccassi
> > <bluca@debian.org>; stable@dpdk.org
> > Subject: [dpdk-dev] [PATCH] net/e1000: do not error out if
> > rx_drop_en is set
> > 
> > rx_drop_en is an optimization that does nothing on single-queue
> > devices like
> > e1000. Do not force applications that do not care to select per-
> > devices
> 
> And aslo, eth_em_rx_queue_setup support set up of multiple queues for
> EM device.
> 
> > optimizations flags by returning an error, just log it and carry
> > on.
> 
> rx_drop_en is a flag to enable receive packets drop when insufficient
> receive descriptors exist to write the packet into system memory.
> if we delete this parameter check protection, it may be misleading
> some applications for this point, why does not give some requirement 
> for proper usage of this? I do not suggest for this change.
> You can also refer to function eth_igb_rx_queue_setup(), igb device
> support rx_drop_en set, so we do not have a such parameter check.

Hi,

As mentioned, because given it does nothing it's not worth aborting the
program with an error. Logging a notice level message and carrying on
is sufficient.
We should try not make it harder than necessary for application
developers.

> > 
> > Fixes: 805803445a02 ("e1000: support EM devices (also known as
> > e1000/e1000e)")
> > Cc: stable@dpdk.org
> > 
> > Signed-off-by: Luca Boccassi <bluca@debian.org>
> > ---
> >  drivers/net/e1000/em_rxtx.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> > 
> > diff --git a/drivers/net/e1000/em_rxtx.c
> > b/drivers/net/e1000/em_rxtx.c
> > index a6b3e92a6..81dc41efb 100644
> > --- a/drivers/net/e1000/em_rxtx.c
> > +++ b/drivers/net/e1000/em_rxtx.c
> > @@ -1416,12 +1416,13 @@ eth_em_rx_queue_setup(struct rte_eth_dev
> > *dev,
> >  	}
> > 
> >  	/*
> > -	 * EM devices don't support drop_en functionality
> > +	 * EM devices don't support drop_en functionality.
> > +	 * It's an optimization that does nothing on single-queue
> > devices,
> > +	 * so just log the issue and carry on.
> >  	 */
> >  	if (rx_conf->rx_drop_en) {
> > -		PMD_INIT_LOG(ERR, "drop_en functionality not
> > supported
> > by "
> > +		PMD_INIT_LOG(NOTICE, "drop_en functionality not
> > supported by "
> >  			     "device");
> > -		return -EINVAL;
> >  	}
> > 
> >  	/* Free memory prior to re-allocation if needed. */
> > --
> > 2.18.0
> 
> 

-- 
Kind regards,
Luca Boccassi