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 E3AE175809; Sun, 22 Mar 2026 10:01:13 +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=1774173674; cv=none; b=P/macuITlWVxgzZyRL4hAq+ssFFyAJdUE3FY9wA/j/n+721fiNBZ0Iz+s6OQa2s3bVwMqRVO7IjCuoP1IFYit9qegh/Pm47a5safdvlmfkBZsa6LTpOP6ZzYh3shfVxvMtlr2GXrklCzFHxrduE6k9T/cTcul6fHEgr5im4kgMk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774173674; c=relaxed/simple; bh=izHFzYTNZF34lEla+82zrFLjgApuyM2q+I2Q/Xn97EE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=XLDuwvCPdfvEIMwCyE+kSzgGKmoVLycB89MANblpoWdtuZ4rTBTYbviW+YYb8YGD/tZbOvcLOba+UAVoZKf7ZcZe/QpkqzdFzuFd69hY4BFKQ1VGlZqgRTE+ytvvB7jy6WMmegrMbLv6QDmB5af5gt3pcuRxjPpy63xtAhXlt/U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NE4XY1so; 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="NE4XY1so" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 892ACC19424; Sun, 22 Mar 2026 10:01:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774173673; bh=izHFzYTNZF34lEla+82zrFLjgApuyM2q+I2Q/Xn97EE=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=NE4XY1souswN6Vh6RquKpO8B5zhT7O1nYa+mWIZpNXzzpT6PiTF0Qr33BU+JLOl/A To/J1x7YctGVvVAbyz/+7AB5M4qtpAG7ubwEQRVmq+hnmXGCH7L4z56nApxrgVdHNs fszQbqe8j+A7uL/5sOiKPnSPDmcZY2n/WWXYYnUeMyfgZVPXxoBhvVyHDyv8cC/jS0 KoWDamXstMz6KXy5U51UYycKQWSSIip+H21l5d9CgKgGIWjMyVs+oQKoR1dtBcnrnP IqVN/Y/GuItLZ8RA5gwxDvGIkcbRut7lwNtRo4gdQzPXP841ibDO2SRnSo6cn7gkG2 MXedQvMswMhwA== Message-ID: Date: Sun, 22 Mar 2026 11:01:09 +0100 Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/2] dt-bindings: trivial-devices: add spi-miso-mosi-loopback To: Francesco Dolcini Cc: Rob Herring , Krzysztof Kozlowski , Conor Dooley , Mark Brown , Francesco Dolcini , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org References: <20260316073547.11437-1-francesco@dolcini.it> <20260316073547.11437-2-francesco@dolcini.it> <20260316085751.GA23443@francesco-nb> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 18/03/2026 15:14, Francesco Dolcini wrote: > >>> linux,spi-loopback-test as a compatible. >>> >>> On the actual HW I have a pins header and a wire between MISO/MOSI. >> >> pins header, if I understood correctly what you are talking about, is a >> connector. Connecting there a jumper to short circuit there is out of >> scope, because it is not part of the board. Thus cannot be send upstream >> DTS, unless it is really embedded in the design like USB-A dongles which >> could not be removed by end user. >> >> Otherwise you could say that every evalkit board can have such device, >> because they all have pin headers... >> >>> >>> I am clearly missing something obvious, any advise is appreciated. >> >> Describe your hardware... Nothing in this patchset helps in >> understanding it. > > Let me describe the need first, and after that I'll describe the HW. > > The need we have is to have a way, with Linux mainline kernel, to test the SPI > functionality (subsystem, driver and the actual HW). So far this was > done using the spidev out-of-tree and with a loopback between the SPI MOSI and > MISO signals. > > We have a variety of HW that have various signals available on some sort of > connector or pins headers [1]. > > This https://docs.toradex.com/112710-mallow-carrier-board_back.png is just one > example, I know you are familiar with this kind of HW, I am writing it here the > link just for completness and for everyone else. Looks like a specific device (hat), not a jumper connecting two pins on the header. > > So yes, your understanding is correct. > > About the HW, we have various test boards, that plugs into this connector(s), > as test fixture, and, with traces on the PCB, they do connect together the SPI > MISO and MOSI signals. > > Here a couple of picture as an example, of the "Aquila Lava HAT", > https://gist.github.com/dolcini/33c332f0b2174a9d495baf7c79341abf I don't think this is anyhow different than all existing cases of people submitting spidev patches. You can have only two choices: 1. Connector. You cannot send bindings for spidev or loopback claiming it is a connector. 2. Actual device plugged there. You need specific compatible for this actual device. The compatible cannot be used for anything else. Best regards, Krzysztof