Re: [PATCH 2/6] net/tap: add speed capabilities

[Pascal Mazon <pascal.mazon@6wind.com>]

On Fri, 3 Mar 2017 15:27:12 +0000
"Wiles, Keith" <keith.wiles@intel.com> wrote:

> 
> > On Mar 3, 2017, at 3:46 AM, Pascal Mazon <pascal.mazon@6wind.com>
> > wrote:
> > 
> > Tap PMD is flexible, it supports any speed.
> > 
> > Signed-off-by: Pascal Mazon <pascal.mazon@6wind.com>
> > ---
> > doc/guides/nics/features/tap.ini |  1 +
> > drivers/net/tap/rte_eth_tap.c    | 35
> > +++++++++++++++++++++++++++++++++++ 2 files changed, 36
> > insertions(+)
> > 
> > diff --git a/doc/guides/nics/features/tap.ini
> > b/doc/guides/nics/features/tap.ini index d9b47a003654..dad5a0561087
> > 100644 --- a/doc/guides/nics/features/tap.ini
> > +++ b/doc/guides/nics/features/tap.ini
> > @@ -9,6 +9,7 @@ Jumbo frame          = Y
> > Promiscuous mode     = Y
> > Allmulticast mode    = Y
> > Basic stats          = Y
> > +Speed capabilities   = Y
> > Unicast MAC filter   = Y
> > Other kdrv           = Y
> > ARMv7                = Y
> > diff --git a/drivers/net/tap/rte_eth_tap.c
> > b/drivers/net/tap/rte_eth_tap.c index 994c8be701c8..6670dfbb35ce
> > 100644 --- a/drivers/net/tap/rte_eth_tap.c
> > +++ b/drivers/net/tap/rte_eth_tap.c
> > @@ -351,6 +351,40 @@ tap_dev_configure(struct rte_eth_dev *dev
> > __rte_unused) return 0;
> > }
> > 
> > +static uint32_t
> > +tap_dev_speed_capa(void)
> > +{
> > +	uint32_t speed = pmd_link.link_speed;
> > +	uint32_t capa = 0;
> > +
> > +	if (speed >= ETH_SPEED_NUM_10M)
> > +		capa |= ETH_LINK_SPEED_10M;
> > +	if (speed >= ETH_SPEED_NUM_100M)
> > +		capa |= ETH_LINK_SPEED_100M;
> > +	if (speed >= ETH_SPEED_NUM_1G)
> > +		capa |= ETH_LINK_SPEED_1G;
> > +	if (speed >= ETH_SPEED_NUM_5G)
> > +		capa |= ETH_LINK_SPEED_2_5G;
> > +	if (speed >= ETH_SPEED_NUM_5G)
> > +		capa |= ETH_LINK_SPEED_5G;
> > +	if (speed >= ETH_SPEED_NUM_10G)
> > +		capa |= ETH_LINK_SPEED_10G;
> > +	if (speed >= ETH_SPEED_NUM_20G)
> > +		capa |= ETH_LINK_SPEED_20G;
> > +	if (speed >= ETH_SPEED_NUM_25G)
> > +		capa |= ETH_LINK_SPEED_25G;
> > +	if (speed >= ETH_SPEED_NUM_40G)
> > +		capa |= ETH_LINK_SPEED_40G;
> > +	if (speed >= ETH_SPEED_NUM_50G)
> > +		capa |= ETH_LINK_SPEED_50G;
> > +	if (speed >= ETH_SPEED_NUM_56G)
> > +		capa |= ETH_LINK_SPEED_56G;
> > +	if (speed >= ETH_SPEED_NUM_100G)
> > +		capa |= ETH_LINK_SPEED_100G;
> 
> In the real world the NIC may only support 50G an not say 10M, so in
> that case this code would be wrong as it would set all of the speeds
> up to 50G. I do not think the code should be changed, but I add a
> comment to tell the developer the issue here. I do not want someone
> copying the code and thinking is i correct for a real device.
> 

That's true for actual hardware. But tap is completely virtual, so
actually it could support any speed (it is limited by userland-kernel
communication speed).

What speed would you rather have the tap PMD report as capable of?

Best regards,
Pascal

> > +
> > +	return capa;
> > +}
> > +
> > static void
> > tap_dev_info(struct rte_eth_dev *dev, struct rte_eth_dev_info
> > *dev_info) {
> > @@ -363,6 +397,7 @@ tap_dev_info(struct rte_eth_dev *dev, struct
> > rte_eth_dev_info *dev_info) dev_info->max_tx_queues =
> > internals->nb_queues; dev_info->min_rx_bufsize = 0;
> > 	dev_info->pci_dev = NULL;
> > +	dev_info->speed_capa = tap_dev_speed_capa();
> > }
> > 
> > static void
> > -- 
> > 2.8.0.rc0
> > 
> 
> Regards,
> Keith
>