Re: [PATCH v6 08/30] dt-bindings: soc: fsl: cpm_qe: cpm1-scc-qmc: Add support for QMC HDLC
From: Krzysztof Kozlowski <hidden>
Date: 2023-09-27 00:38:00
Also in:
alsa-devel, linux-arm-kernel, linux-devicetree, linux-gpio, linuxppc-dev, lkml
On 25/09/2023 15:50, Herve Codina wrote:
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With these details, do you still think I need to change the child (channel) compatible ?From OS point of view, you have a driver binding to this child-level compatible. How do you enforce Linux driver binding based on parent compatible? I looked at your next patch and I did not see it.We do not need to have the child driver binding based on parent.Exactly, that's what I said.quoted
We have to ensure that the child handles a QMC channel and the parent provides a QMC channel. A QMC controller (parent) has to implement the QMC API (include/soc/fsl/qe/qmc.h) and a QMC channel driver (child) has to use the QMC API.How does this solve my concerns? Sorry, I do not understand. Your driver is a platform driver and binds to the generic compatible. How do you solve regular compatibility issues (need for quirks) if parent compatible is not used? How does being QMC compliant affects driver binding and compatibility/quirks? We are back to my original question and I don't think you answered to any of the concerns.Well, to be sure that I understand correctly, do you mean that I should provide a compatible for the child (HDLC) with something like this:--- 8< --- compatible: items: - enum: - fsl,mpc885-qmc-hdlc - fsl,mpc866-qmc-hdlc - const: fsl,cpm1-qmc-hdlc - const: fsl,qmc-hdlc --- 8< ---
Yes, more or less, depending on actual compatibility and SoC-family. Maybe "fsl,cpm1-qmc-hdlc" item in the middle is not needed.
If so, I didn't do that because a QMC channel consumer (driver matching fsl,qmc-hdlc) doesn't contains any SoC specific part.
Just like hundreds of other drivers. :) There is a paragraph about specific compatibles here: https://www.kernel.org/doc/html/latest/devicetree/bindings/writing-schema.html
It uses the channel as a communication channel to send/receive HDLC frames to/from this communication channel. All the specific SoC part is handled by the QMC controller (parent) itself and not by any consumer (child).
OK, so you guarantee in 100% for this hardware and all future (including designs unknown currently), that they will be 100% compatible with existing QMC channel consumer (child, matching fsl,qmc-hdlc) driver, thus there will be no need for any quirk. Specifically, there will be no chances that it would be reasonable to re-use the same driver for child (currently fsl,qmc-hdlc) in different parent. P.S. If you received this email twice, apologies, I have here troubles with internet. Best regards, Krzysztof