Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Subject: Re: [PATCH net-next 5/9] page_pool: don't use driver-set flags field
 directly
To:     Alexander Lobakin <aleksander.lobakin@intel.com>
CC:     "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>,
        Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
        Larysa Zaremba <larysa.zaremba@intel.com>,
        Alexander Duyck <alexanderduyck@fb.com>,
        Jesper Dangaard Brouer <hawk@kernel.org>,
        Ilias Apalodimas <ilias.apalodimas@linaro.org>,
        Simon Horman <simon.horman@corigine.com>,
        <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>
References: <20230727144336.1646454-1-aleksander.lobakin@intel.com>
 <20230727144336.1646454-6-aleksander.lobakin@intel.com>
 <a0be882e-558a-9b1d-7514-0aad0080e08c@huawei.com>
 <6f8147ec-b8ad-3905-5279-16817ed6f5ae@intel.com>
From:   Yunsheng Lin <linyunsheng@huawei.com>
Message-ID: <a7782cf1-e04a-e274-6a87-4952008bcc0c@huawei.com>
Date:   Sat, 29 Jul 2023 19:40:32 +0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101
 Thunderbird/52.2.0
MIME-Version: 1.0
In-Reply-To: <6f8147ec-b8ad-3905-5279-16817ed6f5ae@intel.com>
Content-Type: text/plain; charset="utf-8"
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 2023/7/28 22:03, Alexander Lobakin wrote:
> From: Yunsheng Lin <linyunsheng@huawei.com>
> Date: Fri, 28 Jul 2023 20:36:50 +0800
> 
>> On 2023/7/27 22:43, Alexander Lobakin wrote:
>>
>>>  
>>>  struct page_pool {
>>>  	struct page_pool_params p;
>>> -	long pad;
>>> +
>>> +	bool dma_map:1;				/* Perform DMA mapping */
>>> +	enum {
>>> +		PP_DMA_SYNC_ACT_DISABLED = 0,	/* Driver didn't ask to sync */
>>> +		PP_DMA_SYNC_ACT_DO,		/* Perform DMA sync ops */
>>> +	} dma_sync_act:1;
>>> +	bool page_frag:1;			/* Allow page fragments */
>>>  
>>
>> Isn't it more common or better to just remove the flags field in
>> 'struct page_pool_params' and pass the flags by parameter like
>> below, so that patch 4 is not needed?
>>
>> struct page_pool *page_pool_create(const struct page_pool_params *params,
>> 				   unsigned int	flags);
> 
> You would need a separate patch to convert all the page_pool_create()
> users then either way.
> And it doesn't look really natural to me to pass both driver-set params
> and driver-set flags as separate function arguments. Someone may then
> think "why aren't flags just put in the params itself". The fact that
> Page Pool copies the whole params in the page_pool struct after
> allocating it is internals, page_pool_create() prototype however isn't.
> Thoughts?

It just seems odd to me that dma_map and page_frag is duplicated as we
seems to have the same info in the page_pool->p.flags.

What about:
In [PATCH net-next 4/9] page_pool: shrink &page_pool_params a tiny bit,
'flags' is bit-field'ed with 'dma_dir', what about changing 'dma_dir'
to be bit-field'ed with 'dma_sync_act', so that page_pool->p.flags stays
the same as before, and 'dma_map' & 'page_frag' do not seems be really
needed as we have the same info in page_pool->p.flags?


> 
> Thanks,
> Olek
> 
> .
>