From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 13AA611187; Tue, 26 Nov 2024 18:09:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732644590; cv=none; b=nr18EGvAbUFZYtcw/JgbWYQXqtZirtK8OJ3fxUaHLvCyACt4iw/Tau1yhmuK6w6Ss2HFAFrzX/hnGaoJs5u+2ol4pBOYu0GURJbLqQS/LBgv9AS72i8rF8rI8LtG0unGZpN9jPQSrnwBH/WPD4BFhtyANAlECzDlIyeSCoRS2WY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732644590; c=relaxed/simple; bh=Dn68kwfusM/F6PFzcK9RRMgIKLG8Q2p95XVK2fHrCpI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HdOb3CRsqfe9fYx8NLvdSWQtqA9LkkEO+B9/qVDmz4PC4Y5th0HlDAIA6e+i1PvExQYncUdHqwQSt14MftlBHKY3W7BCpgBc5dryCfvpWsxGJMbxGWa9vpJ/WcjYVKySLUL34scJqwIZcRtQQrWsWc3lJTdzQcJXAiLfYrbyG1I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EqFjblAH; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="EqFjblAH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B27BBC4CECF; Tue, 26 Nov 2024 18:09:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1732644589; bh=Dn68kwfusM/F6PFzcK9RRMgIKLG8Q2p95XVK2fHrCpI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EqFjblAHK+acST9EGdraw8bb/dxcuETdMlcHHy2i1lRe1YVc5tLv+qNV31V6Ab/fU IcrBVFs5YMywsHEUWNBWXWYDqHdQLGadZVOxLIoo+npNxHP62hOvbpPxwvC6jr1dDZ b1gy3AwfIi0HyO7znaTYGuIS92IrJUuIfkAg3fiiPVBlgoOnO8DfZqLoHtqYBXeqTS W+mUh9K6EAxwZLXGOyDtqxWVScl7Opw9Ms4Seyj8uidgfsZSRQ0HXA9GZNALdX/3EN PEdlmZsoef3RyvyalQg2Nm6tJfL2C9jEk6dNSRQdz5PidL7KZOgVxjhzxzD9ADbsee yb2EMIaRpeYog== Date: Tue, 26 Nov 2024 18:09:43 +0000 From: Conor Dooley To: Romain Gantois Cc: Wolfram Sang , Tomi Valkeinen , Luca Ceresoli , Andi Shyti , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Derek Kiernan , Dragan Cvetic , Arnd Bergmann , Greg Kroah-Hartman , Mauro Carvalho Chehab , Linus Walleij , Bartosz Golaszewski , Thomas Petazzoni , Kory Maincent , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, linux-media@vger.kernel.org, linux-gpio@vger.kernel.org Subject: Re: [PATCH v3 1/9] dt-bindings: misc: Describe TI FPC202 dual port controller Message-ID: <20241126-precinct-corrode-516d3a476479@spud> References: <20241125-fpc202-v3-0-34e86bcb5b56@bootlin.com> <20241125-fpc202-v3-1-34e86bcb5b56@bootlin.com> <20241125-overhand-economist-5a3fc6339265@spud> <2072150.UuDqf3iUMg@fw-rgant> Precedence: bulk X-Mailing-List: linux-i2c@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="hkZzaXn6Nj+Xev9H" Content-Disposition: inline In-Reply-To: <2072150.UuDqf3iUMg@fw-rgant> --hkZzaXn6Nj+Xev9H Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Nov 26, 2024 at 09:05:42AM +0100, Romain Gantois wrote: > Hello Conor, >=20 > On lundi 25 novembre 2024 19:26:35 heure normale d=E2=80=99Europe central= e Conor Dooley wrote: > > On Mon, Nov 25, 2024 at 09:45:15AM +0100, Romain Gantois wrote: > > > The FPC202 dual port controller serves as a low speed signal aggregat= or > > > for > ... > > > + > > > +required: > > > + - compatible > > > + - gpio-controller > > > + - "#gpio-cells" > > > + - reg > > > + - "#address-cells" > > > + - "#size-cells" > > > + - i2c@0 > > > + - i2c@1 > >=20 > > btw, why are both downstream ports required? >=20 > It's because both downstream ports are always present in an FPC202 unit > so in my opinion, it doesn't make sense to describe an FPC202 with only o= ne > downstream port. >=20 > I suppose you could also consider that ports would only be described in t= he DT > if they were connected to something in the hardware, but I don't think it= would > make sense to use an FPC202 in this way. After all, the whole point of th= is > component is to act as an I2C ATR and low-speed signal aggregator for > downstream devices which would have address collisions if you placed them > on the same I2C bus. >=20 > But then again, you could consider that DT bindings should only describe = what is > possible, and not only what makes sense as a use case. I don't really kno= w how to > answer this question myself, so I'll refer to the maintainers' opinions. I don't really know what how this device works, which is why I am asking questions. If there is no use case were someone would only wire up one of the downstream ports then making both required is fine. I was just thinking that someone might only hook devices up to one side of it and leave the other unused entirely. Seemed like it could serve its role without both sides being used based on the diagram in https://docs.kernel.org/i2c/i2c-address-translators.html unless it is not possible for the atr to share the "parent" i2c bus with other devices? --hkZzaXn6Nj+Xev9H Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iHUEABYIAB0WIQRh246EGq/8RLhDjO14tDGHoIJi0gUCZ0YO5wAKCRB4tDGHoIJi 0peVAP0Tx4IuAFRG1f+DIwASl/6j0oDlZVMHvalzkyIQp7Ma4QD/WL2qSBDyyW3P hTovWdSEjm5sUQSwdUr2MU+1r5AGpgo= =Hc1y -----END PGP SIGNATURE----- --hkZzaXn6Nj+Xev9H--