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[209.85.217.52]) by smtp.gmail.com with ESMTPSA id 71dfb90a1353d-54a0d1bc289sm2772876e0c.4.2025.09.16.03.15.07 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 16 Sep 2025 03:15:07 -0700 (PDT) Received: by mail-vs1-f52.google.com with SMTP id ada2fe7eead31-5357f3e2520so4010925137.1 for ; Tue, 16 Sep 2025 03:15:07 -0700 (PDT) X-Forwarded-Encrypted: i=1; AJvYcCXRqHwJcNk8eYoFjPmkDgtpcbzAlqIiSzqyNwvLYk+Ki6Nntk10DzjDEIgSP8KWMXHxC0ApdtwH7j49@vger.kernel.org X-Received: by 2002:a67:ff90:0:b0:569:1c73:46c5 with SMTP id ada2fe7eead31-5691c735ffbmr267311137.2.1758017707282; Tue, 16 Sep 2025 03:15:07 -0700 (PDT) Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250902105710.00512c6d@booty> <337281a8-77f9-4158-beef-ae0eda5000e4@beagleboard.org> <20250908145155.4f130aec@bootlin.com> <20250909114126.219c57b8@bootlin.com> <20250911104828.48ef2c0e@bootlin.com> <20250916084631.77127e29@bootlin.com> In-Reply-To: <20250916084631.77127e29@bootlin.com> From: Geert Uytterhoeven Date: Tue, 16 Sep 2025 12:14:54 +0200 X-Gmail-Original-Message-ID: X-Gm-Features: AS18NWCbl1r2QYO00aPBgisYLqrkmJmQ3Y4JYZGczVS7GzKJm4yKut71Lemfvns Message-ID: Subject: Re: Device tree representation of (hotplug) connectors: discussion at ELCE To: Herve Codina Cc: David Gibson , Ayush Singh , Luca Ceresoli , Krzysztof Kozlowski , devicetree@vger.kernel.org, Rob Herring , Jason Kridner , Krzysztof Kozlowski , Conor Dooley , devicetree-compiler@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Petazzoni , Andrew Davis , Wolfram Sang Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Herv=C3=A9, On Tue, 16 Sept 2025 at 08:46, Herve Codina wrot= e: > On Mon, 15 Sep 2025 14:51:41 +1000 > David Gibson wrote: > > On Thu, Sep 11, 2025 at 10:48:28AM +0200, Herve Codina wrote: > > > From the addon board point of view, the only think we can > > > say is "me, as an addon board, I need a connector of type 'foo' and a > > > connector of type 'bar'". > > > > Agreed. > > > > > Also, at base board level, statically defined in the DT > > > connA is described (type 'foo'), connB and connC are > > > described (type 'bar'). > > > > > > The choice to map connA to the type 'foo' connector expected by the a= ddon > > > and the choice to map connB or connC to the type 'bar' connector expe= cted by > > > the addon can only be done at runtime and probably with the help of a= driver > > > that have the knowledge of the 3 connectors. > > > > Agreed. > > > > > I have the feeling that the choice of physical connectors to which th= e addon > > > board is connected to is a human choice when the board is connected. > > > > Yes. Although if the addons have an EEPROM, or some other sort of ID > > register, it may be possible for some connector drivers to probe this. > > Right, I think we agree that a driver is needed to help in the mapping at > least when multiple connectors are involved. I agree you need a driver to read an ID EEPROM. But why would you need a driver if no ID EEPROM is involved? If the connector types on base board and add-on match, it should work. Gr{oetje,eeting}s, Geert --=20 Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k= .org In personal conversations with technical people, I call myself a hacker. Bu= t when I'm talking to journalists I just say "programmer" or something like t= hat. -- Linus Torvalds