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Fri, 10 Jul 2026 23:28:11 +0200 (CEST) Message-ID: <8eed484696b34d828d7df92557c30ae5a6343e80.camel@collabora.com> Subject: Re: [RFC PATCH 1/6] media: mc: Implement shared media graph From: Nicolas Dufresne To: Michael Riesch , Paul Elder , Kieran Bingham , laurent.pinchart@ideasonboard.com Cc: xuhf@rock-chips.com, stefan.klug@ideasonboard.com, dan.scally@ideasonboard.com, jacopo.mondi@ideasonboard.com, linux-media@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org, hverkuil+cisco@kernel.org, ribalda@chromium.org, sakari.ailus@linux.intel.com Date: Fri, 10 Jul 2026 17:28:10 -0400 In-Reply-To: References: <20260619052637.1110672-1-paul.elder@ideasonboard.com> <20260619052637.1110672-2-paul.elder@ideasonboard.com> <178229758404.3075020.12553514371020830845@ping.linuxembedded.co.uk> <178237578321.292172.5229006087283359591@neptunite.rasen.tech> Autocrypt: addr=nicolas.dufresne@collabora.com; prefer-encrypt=mutual; keydata=mDMEaCN2ixYJKwYBBAHaRw8BAQdAM0EHepTful3JOIzcPv6ekHOenE1u0vDG1gdHFrChD /e0J05pY29sYXMgRHVmcmVzbmUgPG5pY29sYXNAbmR1ZnJlc25lLmNhPoicBBMWCgBEAhsDBQsJCA cCAiICBhUKCQgLAgQWAgMBAh4HAheABQkJZfd1FiEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrjo CGQEACgkQ2UGUUSlgcvQlQwD/RjpU1SZYcKG6pnfnQ8ivgtTkGDRUJ8gP3fK7+XUjRNIA/iXfhXMN abIWxO2oCXKf3TdD7aQ4070KO6zSxIcxgNQFtDFOaWNvbGFzIER1ZnJlc25lIDxuaWNvbGFzLmR1Z nJlc25lQGNvbGxhYm9yYS5jb20+iJkEExYKAEECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4 AWIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCaCyyxgUJCWX3dQAKCRDZQZRRKWBy9ARJAP96pFmLffZ smBUpkyVBfFAf+zq6BJt769R0al3kHvUKdgD9G7KAHuioxD2v6SX7idpIazjzx8b8rfzwTWyOQWHC AAS0LU5pY29sYXMgRHVmcmVzbmUgPG5pY29sYXMuZHVmcmVzbmVAZ21haWwuY29tPoiZBBMWCgBBF iEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrGYCGwMFCQll93UFCwkIBwICIgIGFQoJCAsCBBYCAw ECHgcCF4AACgkQ2UGUUSlgcvRObgD/YnQjfi4+L8f4fI7p1pPMTwRTcaRdy6aqkKEmKsCArzQBAK8 bRLv9QjuqsE6oQZra/RB4widZPvphs78H0P6NmpIJ Organization: Collabora Canada Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-gw40z93wvCRsLGCi92mT" User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 --=-gw40z93wvCRsLGCi92mT Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Le vendredi 10 juillet 2026 =C3=A0 22:42 +0200, Michael Riesch a =C3=A9crit= =C2=A0: > Hi Paul, >=20 > On 6/25/26 10:23, Paul Elder wrote: > > [...] > > > > +// TODO figure out locking for when multiple drivers touch the med= ia graph; > > > > +// maybe macros for shared versions? > > >=20 > > > Do you mean for when drivers are trying to change link state directly= ? > >=20 > > I meant for all the operations that act on media device. I'm not sure w= hat > > there is because I didn't really find anything significant, and I found= some > > action point from some meeting notes somewhere that said "deprecate med= ia_ops" > > (not assigned to me) so... >=20 > Oh yes, for some reason this ball ended up in our side of the field. But > actually I think the media_ops are not much of an issue, as you don't > set them when you create the shared media device. Problem solved, right? If we effectively don't need them in any drivers using shared context, let'= s find a place to add a BUG_ON. Nicolas >=20 > > If there aren't any then it's a non-issue, but if there are then I was > > wondering if we need to return the shared media device to the driver (a= s > > opposed to a non-shared regular media device) and use shared versions o= f media > > device functions that have locking. >=20 > +1 > I would recommend that just to be on the safe side. And I think I would > make the shared media device an opaque pointer to make sure that there > won't be any monkey business. >=20 > Thanks and best regards, > Michael >=20 > >=20 > > >=20 > > > > +struct media_device_shared { > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct media_device mdev; > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct list_head members; > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct list_head links; > > > > + > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct list_head list; > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct kref refcount; > > > > + > > > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct device *removed_device= ; > > > > +}; > > > > +[...] --=-gw40z93wvCRsLGCi92mT Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCalFj6gAKCRDZQZRRKWBy 9JLiAP0UOyPyCM16q6zkWSDCSo9l3pmjTa8NL/r1+uhhmnE//gD/ak5D1OcaSFHo 5DM87seeiJSgCkDLAviyDaSDng88TQk= =n4/E -----END PGP SIGNATURE----- --=-gw40z93wvCRsLGCi92mT--