[ofa-general] Re: IB/core: Add creation flags to QPs

[Or Gerlitz]

Jack Morgenstein wrote:
> No, it isn't.  If the customer has an old libibverbs running against a new
> kernel (which uses your bitmap suggestion of bits 0..7), all his apps will fail
> to run (the qp_type passed by the old libibverbs to the new kernel will be
> misinterpreted).
Ok, Jack, I see your point now, sorry for being slow to catch up, so 
with this in mind:
> This means that we are using the 3 LSBs in an enumerated fashion (integers 0..7), so
> we can't use a bitmap here.  This leads us to a mixed field anyway --
> 3 bits for existing QP types (integers 0..6), and 29 bits of bit-map.
Yes, so way we can go the somehow not very elegant way, that is have the 
uverbs code examine the u32 value and if the only non zero bits are 
among the 3 LS ones, uses the values from the old enum and if any of the 
remaining 29 bits are set consider their values under the bit field 
scheme, etc.
>
> Why not just keep things separate, and use the enumeration as is for the existing types,
> and keep the bitmap as a separate "flags" field -- this is much cleaner.
and this means breaking the ABI, correct. If such a breakage is going to 
happen anyway for the merge of XRC into the mainline kernel and the 
official libibverbs as maintained by Roland, I guess this is fine. I see 
now  that the device capabilities enum is managed in bit field fashion 
so at least there the kernel can advertise easily the block-loopback 
support as you did for XRC (below) why have you left 6 unused bits

Or

> enum ibv_device_cap_flags {
>         IBV_DEVICE_RESIZE_MAX_WR        = 1,
>         IBV_DEVICE_BAD_PKEY_CNTR        = 1 <<  1,
>         IBV_DEVICE_BAD_QKEY_CNTR        = 1 <<  2,
>         IBV_DEVICE_RAW_MULTI            = 1 <<  3,
>         IBV_DEVICE_AUTO_PATH_MIG        = 1 <<  4,
>         IBV_DEVICE_CHANGE_PHY_PORT      = 1 <<  5,
>         IBV_DEVICE_UD_AV_PORT_ENFORCE   = 1 <<  6,
>         IBV_DEVICE_CURR_QP_STATE_MOD    = 1 <<  7,
>         IBV_DEVICE_SHUTDOWN_PORT        = 1 <<  8,
>         IBV_DEVICE_INIT_TYPE            = 1 <<  9,
>         IBV_DEVICE_PORT_ACTIVE_EVENT    = 1 << 10,
>         IBV_DEVICE_SYS_IMAGE_GUID       = 1 << 11,
>         IBV_DEVICE_RC_RNR_NAK_GEN       = 1 << 12,
>         IBV_DEVICE_SRQ_RESIZE           = 1 << 13,
>         IBV_DEVICE_N_NOTIFY_CQ          = 1 << 14,
>         IBV_DEVICE_XRC                  = 1 << 20
> };
>