[dpdk-dev] [PATCH v11 1/1] net/af_xdp: introduce AF XDP PMD driver

[Ferruh Yigit]

On 4/5/2019 4:23 PM, Bruce Richardson wrote:
> On Fri, Apr 05, 2019 at 11:05:25PM +0800, Ye Xiaolong wrote:
>> Hi, Ferruh
>>
>> On 04/05, Ferruh Yigit wrote:
>>> On 4/4/2019 9:51 AM, Xiaolong Ye wrote:
>>>> Add a new PMD driver for AF_XDP which is a proposed faster version of
>>>> AF_PACKET interface in Linux. More info about AF_XDP, please refer to [1]
>>>> [2].
>>>>
>>>> This is the vanilla version PMD which just uses a raw buffer registered as
>>>> the umem.
>>>>
>>>> [1] https://fosdem.org/2018/schedule/event/af_xdp/
>>>> [2] https://lwn.net/Articles/745934/
>>>>
>>>> Signed-off-by: Xiaolong Ye <xiaolong.ye at intel.com>
>>>
>>> <...>
>>>
>>>> diff --git a/drivers/net/af_xdp/meson.build b/drivers/net/af_xdp/meson.build
>>>> new file mode 100644
>>>> index 000000000..840c93728
>>>> --- /dev/null
>>>> +++ b/drivers/net/af_xdp/meson.build
>>>> @@ -0,0 +1,19 @@
>>>> +# SPDX-License-Identifier: BSD-3-Clause
>>>> +# Copyright(c) 2019 Intel Corporation
>>>> +
>>>> +if host_machine.system() == 'linux'
>>>> +	bpf_dep = dependency('libbpf', required: false)
>>>> +	if bpf_dep.found()
>>>> +		build = true
>>>> +	else
>>>> +		bpf_dep = cc.find_library('bpf', required: false)
>>>> +		if bpf_dep.found() and cc.has_header('bpf/xsk.h', dependencies: bpf_dep) and cc.has_header('linux/if_xdp.h')
>>>> +			build = true
>>>> +			pkgconfig_extra_libs += '-lbpf'
>>>> +		else
>>>> +			build = false
>>>> +		endif
>>>> +	endif
>>>> +	ext_deps += bpf_dep
>>>> +endif
>>>> +sources = files('rte_eth_af_xdp.c')
>>>
>>> if system is not 'linux', by default build will be 'true', right, so will it try
>>> to build the driver in that case?
>>> What about setting "build = false" before the linux check, so won't need to set
>>> it false again in the if block, only set it true if dependencies found?
>>
>> This is a good catch, we do need to initialize build = false first, otherwise
>> meson/ninja would just try to build af_xdp pmd if system is not linux, which is
>> undesired. Do I need to send a separate patch for this so you can squash it into
>> af_xdp pmd patch?
>>
>>> And can 'ext_deps' go out of if block?
>>
>> If we move `ext_deps += bpf_dep` out of if block and build system is not linux, there
>> would be error "ERROR: Unknown variable "bpf_dep".", so we need either initialize
>> bpf_dep (to value like NULL?) first or keep `ext_deps += bpf_dep` inside the if 
>> block, I'd prefer keep it as it is, what's you opinion?
> 
> Actually, a suggestion - rather than limiting the build to linux, why not
> just limit the build to the presence of libbpf, and not bother checking the
> OS?

If this won't cause a problem for other OS in case they have the library, I have
no objection.