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Thu, 26 Feb 2026 20:45:13 +0100 (CET) Message-ID: <429f3c7aa22eccffedbf8db6aa91bee3dd13814a.camel@collabora.com> Subject: Re: [PATCH v4 1/3] media: dt-bindings: rockchip,vdec: Add alternative reg-names order for RK35{76,88} From: Nicolas Dufresne To: Conor Dooley , Cristian Ciocaltea Cc: Rob Herring , Krzysztof Kozlowski , Conor Dooley , Heiko Stuebner , Detlev Casanova , Ezequiel Garcia , Mauro Carvalho Chehab , Hans Verkuil , kernel@collabora.com, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org, Conor Dooley , linux-media@vger.kernel.org Date: Thu, 26 Feb 2026 14:45:11 -0500 In-Reply-To: <20260226-salute-threaten-a3eabb232396@spud> References: <20260226-vdec-reg-order-rk3576-v4-0-b8d72dc75250@collabora.com> <20260226-vdec-reg-order-rk3576-v4-1-b8d72dc75250@collabora.com> <20260226-salute-threaten-a3eabb232396@spud> 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="=-6UGd8Ri2+YJO1QGD5T1b" User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260226_114519_437602_0E6E09B1 X-CRM114-Status: GOOD ( 34.94 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --=-6UGd8Ri2+YJO1QGD5T1b Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Le jeudi 26 f=C3=A9vrier 2026 =C3=A0 18:43 +0000, Conor Dooley a =C3=A9crit= =C2=A0: > On Thu, Feb 26, 2026 at 12:46:53PM +0200, Cristian Ciocaltea wrote: > > With the introduction of the RK3588 SoC, and RK3576 afterwards, two mor= e > > register blocks have been provided for the video decoder unit. > >=20 > > However, the binding does not properly describe the new hardware layout= , > > as it breaks the convention expecting the unit address to indicate the > > start of the first register range, i.e. 'function' block is listed > > before 'link' instead of the opposite. >=20 > I don't understand this commit message or rationale for an ABI break. > Changing the unit address seems like a "free" fix to your problem, > especially when reg-names is not a required property that you can rely > on. Actually, there may be a bug in the driver - it expects reg-names > for rk3576-vdec and rk3588-vdec but the binding doesn't mandate their > presence for those devices. If the bindings had been held instead of released early, the order would be= what is done in this patch for sure, and no one would have complained. These bin= ding have never been used by anyone so far, and what you are asking is to create= a DTS that deviate from the vendor provided documentation for the IP base add= ress. I know you have all technical fancy reasoning, but I like when things are functional and effective to work with. >=20 > Deprecating the order also makes little sense to me, given that some of > these devices only have one reg entry, which as far as I can tell from > looking at the driver *is* the "function" region, so it can never be > entirely deprecated. What I'd like to see, is a binding expression that behave like a set, not a list, and leave the ordering open. As people keep repeating, there is nothi= ng in a binding that assist to define the right ordering (its not address or base addres aware). That basically means, we can't as reviewer see that ordering= is going to imposing using a base address in the unit name (which is a conveni= ence, not a rule I suppose) that differ from the vendor documented base address. By explicitly removing the ordering in the binding, we create a strict rule= that driver should retrieve this by name, and never assume the ordering, which I personally like. thoughts ? Nicolas >=20 > Confused, > Conor. >=20 > >=20 > > Since the binding changes have been already released and a fix would > > bring up an ABI break, mark the current 'reg-names' ordering as > > deprecated and introduce an alternative 'link,function,cache' listing > > which follows the address-based ordering according to the TRM. > >=20 > > Additionally, drop the 'reg' description items as the order is not fixe= d > > anymore, while the information they offer is not very relevant anyway. > >=20 > > Signed-off-by: Cristian Ciocaltea > > --- > > =C2=A0.../devicetree/bindings/media/rockchip,vdec.yaml=C2=A0=C2=A0=C2= =A0=C2=A0 | 20 ++++++++++++----- > > --- > > =C2=A01 file changed, 12 insertions(+), 8 deletions(-) > >=20 > > diff --git a/Documentation/devicetree/bindings/media/rockchip,vdec.yaml > > b/Documentation/devicetree/bindings/media/rockchip,vdec.yaml > > index 809fda45b3bd..c513b68d2c72 100644 > > --- a/Documentation/devicetree/bindings/media/rockchip,vdec.yaml > > +++ b/Documentation/devicetree/bindings/media/rockchip,vdec.yaml > > @@ -28,16 +28,20 @@ properties: > > =C2=A0 > > =C2=A0=C2=A0 reg: > > =C2=A0=C2=A0=C2=A0=C2=A0 minItems: 1 > > -=C2=A0=C2=A0=C2=A0 items: > > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - description: The function configurati= on registers base > > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - description: The link table configura= tion registers base > > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - description: The cache configuration = registers base > > +=C2=A0=C2=A0=C2=A0 maxItems: 3 > > =C2=A0 > > =C2=A0=C2=A0 reg-names: > > -=C2=A0=C2=A0=C2=A0 items: > > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - const: function > > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - const: link > > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - const: cache > > +=C2=A0=C2=A0=C2=A0 oneOf: > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - items: > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - const: link > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - const: functi= on > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - const: cache > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - items: > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - const: functi= on > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - const: link > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - const: cache > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 deprecated: true > > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 description: Use link,funct= ion,cache block order instead. > > =C2=A0 > > =C2=A0=C2=A0 interrupts: > > =C2=A0=C2=A0=C2=A0=C2=A0 maxItems: 1 > >=20 > > --=20 > > 2.52.0 > >=20 --=-6UGd8Ri2+YJO1QGD5T1b Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCaaCixwAKCRDZQZRRKWBy 9JiHAP4os7RdZaABz35jtFTqxJdGRCHiZ2JyeJsCH7Yj8wqZ1gEAs/hIPqsAIIGJ I/RUZ0zI4YsAWeThrjFOkFlZA7v8NwE= =jF9G -----END PGP SIGNATURE----- --=-6UGd8Ri2+YJO1QGD5T1b--