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 499C8255F52; Wed, 13 May 2026 12:11:38 +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=1778674298; cv=none; b=SJ95P19nAHY+c1pMoX285xZpPzikwoECnKhYgmVVv3DF/dRLxtsR/tppbrulLM1jMjY6gyBVp7f+jY3xVSF0zeMXiaFWGOm1vv7CZ8iOuGvtgGAI85vvlye0x3hYFKdcFzC6Kky6SWKqvoAqqUYXtTN8v3h1vlSaaTcr4aCOfeE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778674298; c=relaxed/simple; bh=yeqD45+3/MnvE3oQPNQ8uNItA+45Oar1Fl18kCZc/WM=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=RSv7nq6utNgTiql15fbLoaIkwCtabS+srlY8AguUxu1PmiCfLcariiybVrR0Gu/t2Pk4eQGMPg3C/z9UZiBx7FjLvmHCspp/3bG/eQm7U47uW5AH2ix7wHSWww6uwVq8uu9MNUlyyyv2RDJjq7+TiQEFIrOcqIB+QlIFrxtLlRw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=JINf5OLU; 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="JINf5OLU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B4E55C2BCB7; Wed, 13 May 2026 12:11:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778674297; bh=yeqD45+3/MnvE3oQPNQ8uNItA+45Oar1Fl18kCZc/WM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JINf5OLUH+jAbvHJsQu+x21GPdJofr0IXr5I3bz2rtGmHyXjYtbl6vk+TEcI/KOrn uNYJOundYhsWnipo5UXGaC9/NU5Ua1g9rPvDjAYCy+B+No2SbEdNawUWQST6lBftOb Em3AgVM6Yai7p+kyJIsieLx1nkN4qFrqBdReY4oD3p/OEoLXtvn6qVi+dUnuyzUUI4 KLWgVS+X8AnOS1/JQoLUC18O0+KljMN/C+YEPEGiWzaVkDJyi7Mb9EtuAwoLKzoryj 0LORofDQN3T+gk+f3iNPZhNpc92VxQY+Qzn6rIM7vzVKrIq0kqthFsbCXa0AWX49YH m4bUT5d9LoQwg== Date: Wed, 13 May 2026 07:11:35 -0500 From: Rob Herring To: Bartosz Golaszewski Cc: Markus Stockhausen , wsa+renesas@sang-engineering.com, andi.shyti@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, linux-i2c@vger.kernel.org, devicetree@vger.kernel.org, Marek Vasut Subject: Re: [PATCH v2 0/2] i2c: Add i2c-shared-gpio driver Message-ID: <20260513121135.GA432696-robh@kernel.org> References: <20260511162528.84508-1-markus.stockhausen@gmx.de> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, May 12, 2026 at 01:00:08PM +0200, Bartosz Golaszewski wrote: > On Mon, May 11, 2026 at 6:25 PM Markus Stockhausen > wrote: > > > > This series adds support for hardware designs where multiple I2C > > gpio based busses are realized with dedicated SDA lines and a > > shared SCL line. This way N busses can be realized with N+1 gpios. > > > > Currently there are several Realtek switches that make use of > > this design. Samples are: > > > > HPE 1920-48G > > Linksys LGS310C > > Zyxel GS1920-24 > > Engenius EWS2910 > > D-Link DGS-1250 > > > > While at first glance this might be a usecase for the new shared > > gpio architecture, discussion and testing shows that this is not > > trivial at all. A shared gpio is handled by a voting system. If > > there at least one user that votes for the GPIO to be "high", > > it stays high. > > > > So the implementation manages several classic bitbang buses with > > locking/unlocking in the pre_xfer/post_xfer handlers. > > > > Signed-off-by: Markus Stockhausen > > > > Hi! > > A couple high-level issues. You'll soon hear from the DT maintainers > and they'll ask if the i2c-shared-gpio compatible corresponds with an > actual piece of hardware on the board. It does not, so the bindings > will be rejected. Perhaps you missed I've already commented on this. I'm actually fine with the binding at a high level. But if we want to model it as N i2c-gpio nodes I'm fine with that as well. Rob