[dpdk-dev] [RFC PATCH] config: remap flags used for Arm platforms

[Ruifeng Wang]

> -----Original Message-----
> From: Bruce Richardson <bruce.richardson at intel.com>
> Sent: Friday, August 14, 2020 6:01 PM
> To: Ruifeng Wang <Ruifeng.Wang at arm.com>
> Cc: hemant.agrawal at nxp.com; jerinj at marvell.com;
> viktorin at rehivetech.com; dev at dpdk.org; Honnappa Nagarahalli
> <Honnappa.Nagarahalli at arm.com>; Phil Yang <Phil.Yang at arm.com>; nd
> <nd at arm.com>
> Subject: Re: [dpdk-dev] [RFC PATCH] config: remap flags used for Arm
> platforms
> 
> On Fri, Aug 14, 2020 at 09:05:23AM +0000, Ruifeng Wang wrote:
> >
> > > -----Original Message-----
> > > From: Bruce Richardson <bruce.richardson at intel.com>
> > > Sent: Friday, August 14, 2020 4:13 PM
> > > To: Ruifeng Wang <Ruifeng.Wang at arm.com>
> > > Cc: hemant.agrawal at nxp.com; jerinj at marvell.com;
> > > viktorin at rehivetech.com; dev at dpdk.org; Honnappa Nagarahalli
> > > <Honnappa.Nagarahalli at arm.com>; Phil Yang <Phil.Yang at arm.com>; nd
> > > <nd at arm.com>
> > > Subject: Re: [dpdk-dev] [RFC PATCH] config: remap flags used for Arm
> > > platforms
> > >
> > > On Fri, Aug 14, 2020 at 02:03:20PM +0800, Ruifeng Wang wrote:
> > > > Flags are used to distinguish different platform architectures.
> > > > These flags can be used to pick different code paths for different
> > > > architectures at compile time.
> > > > For Arm platforms, there are 3 flags in use: RTE_ARCH_ARM,
> > > > RTE_ARCH_ARMv7 and RTE_ARCH_ARM64.
> > > > RTE_ARCH_ARM64 is used to flag 64-bit aarch64 platforms, while
> > > > RTE_ARCH_ARM & RTE_ARCH_ARMv7 are used to flag 32-bit platforms.
> > > > RTE_ARCH_ARMv7 is for ARMv7 platforms as its name suggested.
> > > >
> > > > The issue is that flag name RTE_ARCH_ARM is unclear and could
> > > > cause confusion. No info about platform word length is included in the
> name.
> > > > To make the flag names more clear, a naming scheme is proposed.
> > > >
> > > >       RTE_ARCH_ARM
> > > >           |
> > > >           +----RTE_ARCH_ARM32
> > > >           |        |
> > > >           |        +----RTE_ARCH_ARMv7
> > > >           |        |
> > > >           |        +----RTE_ARCH_ARMv8_AARCH32
> > > >           |
> > > >           +----RTE_ARCH_ARM64
> > > >
> > > > RTE_ARCH_ARM32 will be used for 32-bit Arm platforms.
> > > > It includes RTE_ARCH_ARMv7 and RTE_ARCH_ARMv8_AARCH32.
> > > > RTE_ARCH_ARMv7 is for ARMv7 platforms.
> > > > RTE_ARCH_ARMv8_AARCH32 is for aarch32 state on aarch64 platforms.
> > > > RTE_ARCH_ARM64 is for 64-bit Arm platforms.
> > > > RTE_ARCH_ARM will be used for all Arm platforms, including
> > > > RTE_ARCH_ARM32 and RTE_ARCH_ARM64.
> > > >
> > > > To fit into the new naming scheme, current usage of RTE_ARCH_ARM
> > > > in project code is mapped to RTE_ARCH_ARM32.
> > > >
> > > > Suggested-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>
> > > > Signed-off-by: Ruifeng Wang <ruifeng.wang at arm.com>
> > > > Reviewed-by: Phil Yang <phil.yang at arm.com>
> > > > ---
> > > Just to note that for all architectures there is the RTE_ARCH_64
> > > define which is set if the system is 64-bit. That could be used
> > > instead if you didn't want to have to specially define ARM32 and ARM64
> macros.
> > >
> > Yes. Thanks for the note.
> > RTE_ARCH_ARM64 is used in architecture specific cases. For example,
> > when a processing path is not implemented by some of 64-bit architectures,
> RTE_ARCH_64 is not sufficient.
> >
> Yes, but is RTE_ARCH_ARM64 not identical to RTE_ARCH_ARM &&
> RTE_ARCH_64?

My thought is:
1. RTE_ARCH_ARM64 is a direct macro, so with better readability.
2. RTE_ARCH_ARM64 is already used widely in the project.
So I think it is better not to replace the occurrences with combination of other macros.