Re: [dpdk-dev] [RFC PATCH v1] build: add platform meson option

[Bruce Richardson <bruce.richardson@intel.com>]

On Thu, Nov 26, 2020 at 04:47:29PM +0100, Juraj Linkeš wrote:
> The current meson option 'machine' should only specify the ISA, which is
> not sufficient for Arm, where setting ISA implies other setting as well.
> Add a new meson option, 'platform', which differentiates the type of the
> build (native/generic) and sets machine accordingly, unless the user
> chooses to override it.
> 
> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> ---
>  config/arm/meson.build |  2 +-
>  config/meson.build     | 14 +++++++++++++-
>  meson_options.txt      |  6 ++++--
>  3 files changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/config/arm/meson.build b/config/arm/meson.build
> index 42b4e43c7..ac680956f 100644
> --- a/config/arm/meson.build
> +++ b/config/arm/meson.build
> @@ -6,7 +6,7 @@
>  march_opt = '-march=@0@'.format(machine)
>  
>  arm_force_native_march = false
> -arm_force_default_march = (machine == 'default')
> +arm_force_default_march = (platform == 'generic')
>  
>  flags_common_default = [
>  	# Accelarate rte_memcpy. Be sure to run unit test (memcpy_perf_autotest)
> diff --git a/config/meson.build b/config/meson.build
> index c02802c18..41d32e63e 100644
> --- a/config/meson.build
> +++ b/config/meson.build
> @@ -63,6 +63,8 @@ if not is_windows
>  			pmd_subdir_opt)
>  endif
>  
> +platform = get_option('platform')
> +
>  # set the machine type and cflags for it
>  if meson.is_cross_build()
>  	machine = host_machine.cpu()
> @@ -70,13 +72,23 @@ else
>  	machine = get_option('machine')
>  endif
>  
> +if platform == 'native'
> +	if machine == 'auto'
> +		machine = 'native'
> +	endif
> +elif platform == 'generic'
> +	if machine == 'auto'
> +		machine = 'default'
> +	endif
> +endif
> +
> +if machine == 'default'
>  # machine type 'default' is special, it defaults to the per arch agreed common
>  # minimal baseline needed for DPDK.
>  # That might not be the most optimized, but the most portable version while
>  # still being able to support the CPU features required for DPDK.
>  # This can be bumped up by the DPDK project, but it can never be an
>  # invariant like 'native'
> -if machine == 'default'
>  	if host_machine.cpu_family().startswith('x86')
>  		# matches the old pre-meson build systems default
>  		machine = 'corei7'
> diff --git a/meson_options.txt b/meson_options.txt
> index e384e6dbb..1a5e47fd3 100644
> --- a/meson_options.txt
> +++ b/meson_options.txt
> @@ -20,14 +20,16 @@ option('kernel_dir', type: 'string', value: '',
>  	description: 'Path to the kernel for building kernel modules. Headers must be in $kernel_dir/build. Modules will be installed in $DEST_DIR/$kernel_dir/extra/dpdk.')
>  option('lib_musdk_dir', type: 'string', value: '',
>  	description: 'path to the MUSDK library installation directory')
> -option('machine', type: 'string', value: 'native',
> -	description: 'set the target machine type')
> +option('machine', type: 'string', value: 'auto',
> +	description: 'set the target machine type/ISA')
>  option('max_ethports', type: 'integer', value: 32,
>  	description: 'maximum number of Ethernet devices')
>  option('max_lcores', type: 'integer', value: 128,
>  	description: 'maximum number of cores/threads supported by EAL')
>  option('max_numa_nodes', type: 'integer', value: 4,
>  	description: 'maximum number of NUMA nodes supported by EAL')
> +option('platform', type: 'string', value: 'generic',
> +	description: 'Platform to build for, either "native" or "generic".')

As well as this short description option, I think we need more
comprehensive coverage of this option in the docs. Presumably for ARM
systems this will have other options for various SOC's rather than just
generic/native?

/Bruce