linux-kernel - Re: [PATCH net-next 5/9] page_pool: don't use driver-set flags field directly

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Message-ID: <03124fbf-1b47-99e1-d9a5-a9251890f6e7@huawei.com>
Date:   Wed, 2 Aug 2023 19:36:17 +0800
From:   Yunsheng Lin <linyunsheng@...wei.com>
To:     Alexander Lobakin <aleksander.lobakin@...el.com>
CC:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Larysa Zaremba <larysa.zaremba@...el.com>,
        Alexander Duyck <alexanderduyck@...com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Simon Horman <simon.horman@...igine.com>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 5/9] page_pool: don't use driver-set flags field
 directly

On 2023/8/1 21:36, Alexander Lobakin wrote:

>>
>> 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.
> 
> It's just because we copy the whole &page_pool_params passed by the
> driver. It doesn't look good to me to define a new structure and copy
> the values field-by-field just to avoid duplicating 3 bits :s
> 
>>
>> 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?
> 
> Not sure I follow :z ::dma_dir is also passed by the driver, so we can't
> drop it from the params struct.

My bad, I missed that dma_dir is in the params struct.