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Wed, 25 Mar 2020 06:49:31 -0700 (PDT) Date: Wed, 25 Mar 2020 15:49:21 +0200 From: Pekka Paalanen To: Neil Armstrong Subject: Re: [PATCH v4 7/8] drm/fourcc: amlogic: Add modifier definitions for the Scatter layout Message-ID: <20200325154921.2a87930c@eldfell.localdomain> In-Reply-To: References: <20200325085025.30631-1-narmstrong@baylibre.com> <20200325085025.30631-8-narmstrong@baylibre.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200325_064937_007078_D60DBCEF X-CRM114-Status: GOOD ( 16.51 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "mjourdan@baylibre.com" , Simon Ser , "linux-kernel@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , Kevin Hilman , "linux-amlogic@lists.infradead.org" , "linux-arm-kernel@lists.infradead.org" Content-Type: multipart/mixed; boundary="===============8501006469541730692==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============8501006469541730692== Content-Type: multipart/signed; micalg=pgp-sha256; boundary="Sig_/e3_VDQSNvzbMkOgJtm//89P"; protocol="application/pgp-signature" --Sig_/e3_VDQSNvzbMkOgJtm//89P Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Wed, 25 Mar 2020 11:24:15 +0100 Neil Armstrong wrote: > Hi, >=20 > On 25/03/2020 10:04, Simon Ser wrote: > > On Wednesday, March 25, 2020 9:50 AM, Neil Armstrong wrote: > > =20 > >> Amlogic uses a proprietary lossless image compression protocol and for= mat > >> for their hardware video codec accelerators, either video decoders or > >> video input encoders. > >> > >> This introduces the Scatter Memory layout, means the header contains I= OMMU > >> references to the compressed frames content to optimize memory access > >> and layout. > >> > >> In this mode, only the header memory address is needed, thus the conte= nt > >> memory organization is tied to the current producer execution and cann= ot > >> be saved/dumped neither transferrable between Amlogic SoCs supporting = this > >> modifier. =20 > >=20 > > I don't think this is suitable for modifiers. User-space relies on > > being able to copy a buffer from one machine to another over the > > network. It would be pretty annoying for user-space to have a blacklist > > of modifiers that don't work this way. > >=20 > > Example of such user-space: > > https://gitlab.freedesktop.org/mstoeckl/waypipe/ > > =20 >=20 > I really understand your point, but this is one of the use-cases we need = solve. > This is why I split the fourcc patch and added an explicit comment. >=20 > Please point me a way to display such buffer, the HW exists, works like t= hat and > it's a fact and can't change. >=20 > It will be the same for secure zero-copy buffers we can't map from usersp= ace, but > only the HW decoder can read/write and HW display can read. The comparison to secure buffers is a good one. Are buffers with the DRM_FORMAT_MOD_AMLOGIC_FBC_LAYOUT_SCATTER modifier meaningfully mmappable to CPU always / sometimes / never / varies-and-cannot-know? Maybe this type should be handled similar to secure buffers, with the exception that they are not actually secured but only mostly inaccessible. Then again, I haven't looked at any of the secure buffer proposals. Thanks, pq --Sig_/e3_VDQSNvzbMkOgJtm//89P Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEJQjwWQChkWOYOIONI1/ltBGqqqcFAl57YWEACgkQI1/ltBGq qqdFJQ//cD3K85nsCGKhXDmSyQzaQzhmiNbd/rn5U392CpaELlvtHKVFtGggN5zp l5MIb/EjYgZUHG220KklqCiZAzk+RLTmZnQPZmXPAnKobeeJLIGwHhKFBTozKG8t 9NLG8Gp1brFA7xVz63SSmZTUWFw4LP+HnMRIPPEGEpx6J4J3MJ8ikC+Utcvcs8yZ 1Be4E8s6cLRxcJPt4Q8PwhTNXtwdPxBL8aGhYB93Ptu30fGACCmUKCCtNyEo7PN+ qK2+eyZh3kB6Ktujsi+QqWgxtzIWtRH67ezkp3TlrqfFDQ8kH5guzfFfjb6coXW9 evJLwTgHoU/WZaOve3WVajKqfJdCbzzKFqBjaIeeA8RTWyWwHeBDpFA/G859H1OQ zd03sTrUz+uOl/k9ZpyG7dvReAijUA450FQe+c59lDWwWV94tRwbrFbjI3yh7R5q pl1bpuCFj5BVA74GEc8VzSNuqmqnqDltkiVAJ2BDi2heB5+2Pt+xZQlXz4rY4Ynl y9VLeSXlDxS7eJwsYjN9i3ra182eddULpxbdbdxPF7OVhpG2Wdhr7BFzdiNakBCM V7P7YUwFTOoNhiotZEKVpAnCQ7tIQgDxWRD/va+m6EmMhnjh0jDzb7nKz2a9y1FN UTiMucJoHEe0bxz94KaioKsNKAZQf7cNK1aUPkPF5qH+ORGgdVc= =oJGl -----END PGP SIGNATURE----- --Sig_/e3_VDQSNvzbMkOgJtm//89P-- --===============8501006469541730692== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============8501006469541730692==--