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From: Shakeel Butt <shakeelb@google.com>
Date: Fri, 15 Dec 2023 08:47:46 -0800
Message-ID: <CALvZod7-WsxLj8gdhu=FMfdunEDgBV+DwfOB2316NfXvf_K41g@mail.gmail.com>
Subject: Re: [RFC PATCH net-next v1 4/4] net: page_pool: use netmem_t instead
 of struct page in API
To: Yunsheng Lin <linyunsheng@huawei.com>
Cc: Mina Almasry <almasrymina@google.com>, linux-kernel@vger.kernel.org, 
	netdev@vger.kernel.org, bpf@vger.kernel.org, 
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, 
	Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org, 
	"H. Peter Anvin" <hpa@zytor.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, 
	"Rafael J. Wysocki" <rafael@kernel.org>, Sumit Semwal <sumit.semwal@linaro.org>, 
	=?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>, 
	Michael Chan <michael.chan@broadcom.com>, "David S. Miller" <davem@davemloft.net>, 
	Eric Dumazet <edumazet@google.com>, Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>, 
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	Sean Wang <sean.wang@mediatek.com>, Mark Lee <Mark-MC.Lee@mediatek.com>, 
	Lorenzo Bianconi <lorenzo@kernel.org>, Matthias Brugger <matthias.bgg@gmail.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>, 
	Saeed Mahameed <saeedm@nvidia.com>, Leon Romanovsky <leon@kernel.org>, 
	Horatiu Vultur <horatiu.vultur@microchip.com>, UNGLinuxDriver@microchip.com, 
	"K. Y. Srinivasan" <kys@microsoft.com>, Haiyang Zhang <haiyangz@microsoft.com>, Wei Liu <wei.liu@kernel.org>, 
	Dexuan Cui <decui@microsoft.com>, Jassi Brar <jaswinder.singh@linaro.org>, 
	Ilias Apalodimas <ilias.apalodimas@linaro.org>, 
	Alexandre Torgue <alexandre.torgue@foss.st.com>, Jose Abreu <joabreu@synopsys.com>, 
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	Ravi Gunasekaran <r-gunasekaran@ti.com>, Roger Quadros <rogerq@kernel.org>, 
	Jiawen Wu <jiawenwu@trustnetic.com>, Mengyuan Lou <mengyuanlou@net-swift.com>, 
	Ronak Doshi <doshir@vmware.com>, VMware PV-Drivers Reviewers <pv-drivers@vmware.com>, 
	Ryder Lee <ryder.lee@mediatek.com>, Shayne Chen <shayne.chen@mediatek.com>, 
	Kalle Valo <kvalo@kernel.org>, Juergen Gross <jgross@suse.com>, 
	Stefano Stabellini <sstabellini@kernel.org>, 
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	=?UTF-8?B?TWlja2HDq2wgU2FsYcO8bg==?= <mic@digikod.net>, 
	Nathan Chancellor <nathan@kernel.org>, Nick Desaulniers <ndesaulniers@google.com>, 
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On Fri, Dec 15, 2023 at 3:04=E2=80=AFAM Yunsheng Lin <linyunsheng@huawei.co=
m> wrote:
>
> On 2023/12/15 10:11, Shakeel Butt wrote:
> > On Thu, Dec 14, 2023 at 08:27:55AM -0800, Mina Almasry wrote:
> >> On Thu, Dec 14, 2023 at 4:05=E2=80=AFAM Yunsheng Lin <linyunsheng@huaw=
ei.com> wrote:
> >>>
> > [...]
> >>> I perfer the second one personally, as devmem means that it is not
> >>> readable from cpu.
> >>
> >> From my POV it has to be the first one. We want to abstract the memory
> >> type from the drivers as much as possible, not introduce N new memory
> >> types and ask the driver to implement new code for each of them
> >> separately.
>
> That was my initial thinking too:
> https://www.spinics.net/lists/netdev/msg949376.html
>
> But after discussion, it may make more sense to have two sets of API from=
 the
> driver's piont of view if we want a complete safe type protection, so tha=
t
> compiler can check everything statically and devmem driver API have a cle=
ar
> semantic:
> 1. devmem is not allowed to be called into mm subsystem.
> 2. it will not provide a API like page_address().
>

I think all of us are on the same page that there will be two sets of
APIs here but Mina's point was let's aim to not make that N set of
APIs.