Re: [dpdk-dev] [PATCH v5 3/8] ethdev: reserve capability flags for PMD-specific API

[Tiwei Bie <tiwei.bie@intel.com>]

On Wed, Jan 04, 2017 at 10:21:08PM +0800, Ananyev, Konstantin wrote:
> Hi Twei,
> 
> > -----Original Message-----
> > From: Bie, Tiwei
> > Sent: Wednesday, January 4, 2017 7:22 AM
> > To: dev@dpdk.org
> > Cc: adrien.mazarguil@6wind.com; Lu, Wenzhuo <wenzhuo.lu@intel.com>; Mcnamara, John <john.mcnamara@intel.com>;
> > olivier.matz@6wind.com; thomas.monjalon@6wind.com; Ananyev, Konstantin <konstantin.ananyev@intel.com>; Zhang, Helin
> > <helin.zhang@intel.com>; Dai, Wei <wei.dai@intel.com>; Wang, Xiao W <xiao.w.wang@intel.com>
> > Subject: [PATCH v5 3/8] ethdev: reserve capability flags for PMD-specific API
> > 
> > Reserve a Tx capability flag and a Rx capability flag, that can be
> > used by PMD to define its own capability flags when implementing the
> > PMD-specific API.
> > 
> > Suggested-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
> > Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
> > Acked-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
> > ---
> >  lib/librte_ether/rte_ethdev.h | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/lib/librte_ether/rte_ethdev.h b/lib/librte_ether/rte_ethdev.h
> > index d465825..8800b39 100644
> > --- a/lib/librte_ether/rte_ethdev.h
> > +++ b/lib/librte_ether/rte_ethdev.h
> > @@ -857,6 +857,7 @@ struct rte_eth_conf {
> >  #define DEV_RX_OFFLOAD_TCP_LRO     0x00000010
> >  #define DEV_RX_OFFLOAD_QINQ_STRIP  0x00000020
> >  #define DEV_RX_OFFLOAD_OUTER_IPV4_CKSUM 0x00000040
> > +#define DEV_RX_OFFLOAD_RESERVED_0  0x00000080 /**< Used for PMD-specific API. */
> > 
> >  /**
> >   * TX offload capabilities of a device.
> > @@ -874,6 +875,7 @@ struct rte_eth_conf {
> >  #define DEV_TX_OFFLOAD_GRE_TNL_TSO      0x00000400    /**< Used for tunneling packet. */
> >  #define DEV_TX_OFFLOAD_IPIP_TNL_TSO     0x00000800    /**< Used for tunneling packet. */
> >  #define DEV_TX_OFFLOAD_GENEVE_TNL_TSO   0x00001000    /**< Used for tunneling packet. */
> > +#define DEV_TX_OFFLOAD_RESERVED_0  0x00002000 /**< Used for PMD-specific API. */
> > 
> >  /**
> >   * Ethernet device information
> > --
> > 2.7.4
> 
> I am not sure how that supposed to work and how user should know that DEV_RX_OFFLOAD_RESERVED_0  
> is actually a MACSEC for ixgbe?

Users are not supposed to use DEV_RX_OFFLOAD_RESERVED_0, instead, they
should use the capabilities and the likes defined in rte_pmd_ixgbe.h
where the PMD-specifics APIs are declared:

/**
 * If these flags are advertised by the PMD, the NIC supports the MACsec
 * offload. The incoming MACsec traffics can be offloaded transparently
 * after the MACsec offload is configured correctly by the application.
 * And the application can set the PKT_TX_IXGBE_MACSEC flag in mbufs to
 * enable the MACsec offload for the packets to be transmitted.
 */
#define DEV_RX_OFFLOAD_IXGBE_MACSEC_STRIP	DEV_RX_OFFLOAD_RESERVED_0
#define DEV_TX_OFFLOAD_IXGBE_MACSEC_INSERT	DEV_TX_OFFLOAD_RESERVED_0

/**
 * This event will occur when the PN counter in a MACsec connection
 * reach the exhaustion threshold.
 */
#define RTE_ETH_EVENT_IXGBE_MACSEC		RTE_ETH_EVENT_RESERVED_0

/**
 * Offload the MACsec. This flag must be set by the application in mbuf
 * to enable this offload feature for a packet to be transmitted.
 */
#define PKT_TX_IXGBE_MACSEC			PKT_TX_RESERVED_0

PMD-specific APIs can only be used on the corresponding driver/device,
so different PMD can share the same reserved bit to represent different
things when implementing their own PMD-specific APIs.

> Another question what to do if you would like to create a bonded device over two devices with different NIC types?
> As I understand you can end up in situation when  DEV_RX_OFFLOAD_RESERVED_0  would mean different capabilities.
> Why not to have this MACSEC capability and ol_flag value as generic ones, as you have them in previous versions of your patch?

Those flags are only used in PMD-specific APIs. I don't think we could
use the PMD-specific APIs provided by a certain PMD on a bonded device.

Thanks & regards,
Tiwei Bie