Re: [dpdk-dev] [PATCH v4 1/8] common/sfc_efx/base: add base virtio support for vDPA

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 3/16/2021 12:14 PM, Andrew Rybchenko wrote:
> On 3/16/21 2:58 PM, Ferruh Yigit wrote:
>> On 3/16/2021 11:47 AM, Andrew Rybchenko wrote:
>>> On 3/16/21 2:30 PM, Ferruh Yigit wrote:
>>>> On 3/16/2021 8:58 AM, Andrew Rybchenko wrote:
>>>>> From: Vijay Srivastava <vijays@solarflare.com>
>>>>>
>>>>> In the vDPA mode, only data path is offloaded in the hardware and
>>>>> control path still goes through the hypervisor and it configures
>>>>> virtqueues via vDPA driver so new virtqueue APIs are required.
>>>>>
>>>>> Implement virtio init/fini and virtqueue create/destroy APIs.
>>>>>
>>>>> Signed-off-by: Vijay Srivastava <vijays@solarflare.com>
>>>>> Signed-off-by: Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>
>>>>
>>>> <...>
>>>>
>>>>> diff --git a/drivers/common/sfc_efx/efsys.h
>>>>> b/drivers/common/sfc_efx/efsys.h
>>>>> index 663601412e..d133d61b3d 100644
>>>>> --- a/drivers/common/sfc_efx/efsys.h
>>>>> +++ b/drivers/common/sfc_efx/efsys.h
>>>>> @@ -187,6 +187,8 @@ prefetch_read_once(const volatile void *addr)
>>>>>       #define EFSYS_OPT_MAE 1
>>>>>     +#define EFSYS_OPT_VIRTIO 0
>>>>> +
>>>>
>>>> Hi Andrew,
>>>>
>>>> How this 'efsys.h' works, is it compile time configuration file for the
>>>> driver?
>>>
>>> Yes, it is a compile time configuration of the base driver.
>>>
>>>> Is is expected that users change this file?
>>>
>>> Client drivers (e.g. net/sfc or vdpa/sfc) change the base
>>> driver configuration when it needs corresponding functionality
>>> from the base driver. Of course, it is not ideal to add code
>>> which is not actually compiled right now, but we always try
>>> to ensure that build finally works fine and no extra patches
>>> will be required to fix the build when corresponding option
>>> is enabled.
>>>
>>> In theory we can send longer patch series which includes
>>> the vdpa/sfc driver, but it will be longer patch series which
>>> is harder to chew.
>>>
>>
>> It is OK to send preparation sets first, that wasn't my point.
> 
> I see.
> 
>> My concern is having compile time configuration within driver, my
>> question is if end user of the driver need to tweak these config
>> options, if so should it be more generic way instead of a PMD specific
>> way...
> 
> No, it is not a user configuration. It is configuration done by
> client (net/sfc, vdpa/sfc) drivers which use the common driver.
> 

OK, thanks for clarification.