From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail11.truemail.it (mail11.truemail.it [217.194.8.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6FF01382F19; Mon, 16 Mar 2026 08:57:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.194.8.81 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773651480; cv=none; b=DEkIbWu9FGsrl+s2faK6RKkJQusHoDRSNSCQfVHJ3sKklLH54aN3J7ONnQDZjwTZ4d3k4mMeRO0UFHM1nGNen3b1XzVQY7QMLVsoY866JEAJcnWEi5U8/e0uss/P8uAu23PvxsVk8Vt5VNtRARBGeM15Eem771/JgKBfCr6I7vQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773651480; c=relaxed/simple; bh=ZxsI3XQxON47nNiV9zmlJuSvAruAO15iYIHb6gCgR0o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=U1F40bfrOTgKXDi0xami20G6yag/fD4O7b0B02soz0q6vCcbaiy38Llui63YAX4IcqxltSpwq0O+d/yGBzZzDKWmYEFjxopW9W4WkOwdXG2HVHDVSgxiSjph2jVjRhfY6YztLE9LfyJqAKt6940PaNXsqiPm4A3lW7yNnbVZjgk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=dolcini.it; spf=pass smtp.mailfrom=dolcini.it; dkim=pass (2048-bit key) header.d=dolcini.it header.i=@dolcini.it header.b=iXmIBcqU; arc=none smtp.client-ip=217.194.8.81 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=dolcini.it Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=dolcini.it Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=dolcini.it header.i=@dolcini.it header.b="iXmIBcqU" Received: from francesco-nb (248.201.173.83.static.wline.lns.sme.cust.swisscom.ch [83.173.201.248]) by mail11.truemail.it (Postfix) with ESMTPA id 1F42D1FAAD; Mon, 16 Mar 2026 09:57:56 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=dolcini.it; s=default; t=1773651476; bh=5R8Z9Bm5xjSYnQuak4C93SINyY64xeZH1KNKR5DjkHc=; h=From:To:Subject; b=iXmIBcqUiLMFqcUu29xFNzqVO2Abxkv2Zv6NnbA6W9PCZCgj/ZHFV3lRlE87lhT1D L2/4mkUsCsZFJFP1NfU717T4AGvQOahH31MMPETzVvpmYG5NuPfAG3jXl8zIpGappG rAHopOTDKMPJjhQylONV451JeL1mrriO7zSa0ayPMLSNyrr8PATB73ESjt5vThH66M xTTQjM01cMTrB4WnHY2Gk4cXgJFFat9HIowhO2jjLoopMZ1tGfRy9iEyhJ1eyQBGov 7KNjnzst1CkkTFHCBJGAJ3P/RxUdZawyRTlwdMLKq735hWZ9sE4Gs/WZ87R1SL2Jkg bytpv65quvtkw== Date: Mon, 16 Mar 2026 09:57:51 +0100 From: Francesco Dolcini To: Krzysztof Kozlowski Cc: Francesco Dolcini , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Mark Brown , Francesco Dolcini , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org Subject: Re: [PATCH v1 1/2] dt-bindings: trivial-devices: add spi-miso-mosi-loopback Message-ID: <20260316085751.GA23443@francesco-nb> References: <20260316073547.11437-1-francesco@dolcini.it> <20260316073547.11437-2-francesco@dolcini.it> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Hello Krzysztof, thanks for taking the time to answer this On Mon, Mar 16, 2026 at 09:36:42AM +0100, Krzysztof Kozlowski wrote: > On 16/03/2026 09:35, Krzysztof Kozlowski wrote: > > On 16/03/2026 08:35, Francesco Dolcini wrote: > >> From: Francesco Dolcini > >> > >> Add a compatible to describe a single wire loopback between SPI MISO and > >> MOSI signals. > >> > >> Link: https://lore.kernel.org/all/20260310133254.GA51497@francesco-nb/ > >> Signed-off-by: Francesco Dolcini > >> --- > >> Documentation/devicetree/bindings/trivial-devices.yaml | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/Documentation/devicetree/bindings/trivial-devices.yaml b/Documentation/devicetree/bindings/trivial-devices.yaml > >> index a482aeadcd44..2cb973c157f6 100644 > >> --- a/Documentation/devicetree/bindings/trivial-devices.yaml > >> +++ b/Documentation/devicetree/bindings/trivial-devices.yaml > >> @@ -432,6 +432,8 @@ properties: > >> - socionext,uniphier-smpctrl > >> # SparkFun Qwiic Joystick (COM-15168) with i2c interface > >> - sparkfun,qwiic-joystick > >> + # Single wire loopback between SPI MISO and MOSI signals > >> + - spi-miso-mosi-loopback > > > > If you decided to go against my approach, then at least document it in > > proper place - incomplete-devices - so this won't be ever used in DTS. > > > > ... and then you will notice existing linux,spi-loopback-test, so > explain the differences and why spi-loopback-test cannot be used for > your loopback test. Yes, this spi-loopback-test will work. I was not aware of it (no-one mentioned it in the email thread I opened) and I misread your answer as an alternative suggestion, and not as a nack. There is still an open question, I can any driver probe/bind to the actual SPI device? My plan, once this discussion is settled, is to send patches to add dtso file enabling this test, however, according to trivial-devices.yaml, I cannot submit such a DT file using linux,spi-loopback-test as a compatible. On the actual HW I have a pins header and a wire between MISO/MOSI. I am clearly missing something obvious, any advise is appreciated. Thanks, Francesco