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[72.83.177.149]) by smtp.gmail.com with ESMTPSA id dt5-20020a05620a478500b006ee94c5bf26sm2782237qkb.91.2022.10.18.09.44.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 18 Oct 2022 09:44:24 -0700 (PDT) Message-ID: Date: Tue, 18 Oct 2022 12:44:22 -0400 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.4.0 Subject: Re: [PATCH 09/15] dt-bindings: phy: qcom,qmp-pcie: mark current bindings as legacy Content-Language: en-US To: Johan Hovold Cc: Dmitry Baryshkov , Johan Hovold , Vinod Koul , Andy Gross , Bjorn Andersson , Konrad Dybcio , Rob Herring , Krzysztof Kozlowski , linux-arm-msm@vger.kernel.org, linux-phy@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org References: <20221017145328.22090-1-johan+linaro@kernel.org> <20221017145328.22090-10-johan+linaro@kernel.org> From: Krzysztof Kozlowski In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 18/10/2022 12:04, Johan Hovold wrote: > On Tue, Oct 18, 2022 at 11:32:07AM -0400, Krzysztof Kozlowski wrote: >> On 18/10/2022 07:37, Dmitry Baryshkov wrote: >>> >>>>> And yes, I think we should also upgrade >>>>> older DTs, keeping drivers backwards compatible (for some time?). >>>> >>>> Possibly, but I'm not sure it's worth the dts churn. As I mentioned >>>> elsewhere, supporting both the old and new binding in the driver is >>>> mostly trivial, while encoding the deprecated bindings in DT schema >>>> sounds like it would be painful. >>> >>> This is probably the time where Krzysztof can advise us. I'm still not >>> sure when it is expected to encode both old and new bindings in the >>> schema and when we can update both the schema and the DT. >> >> I do not follow what exactly the proposal is. Are you asking whether to: >> 1. keep existing DTS compatible with old driver? >> or >> 2. update existing DTS so it is working only with new driver (and not >> compatible with old driver thus having ABI break)? >> >> If so, it is less question to bindings but more to the usage of DTS in >> other projects (like bootloaders, firmware, BSD) and generic >> recommendation is: do not break other users, if possible. It is however >> up to the platform maintainer (Bjorn) to decide on this, not on me. > > The question is whether to convert also the current bindings and DTS to > the new (sc8280xp) scheme (e.g. drop the child nodes and register > subregions). > > The driver can support both binding schemes using the same compatible > strings for a transition period (or in theory forever) by checking for > the existence of a child node. > > Converting the DTS to use the new bindings would obviously prevent using > them with an old kernel (i.e. 2 above), but I don't think that's a > problem (unlike backward compatibility during at least a transition > period). It is still not nice towards any other users of DTS, because this will break all of them. I agree this won't be ABI type of break. It is discouraged though, unless there are clear benefits from this or one totally does not care about other DTS users... As I said it is up to platform maintainer. > > My concern was how to describe the deprecation in DT schema if we were > convert them. By instead just keeping the old bindings as-is in a > separate file and continuing to support them in the driver we can have a > nice and clean description of the new bindings (sc8280xp) without the > legacy cruft. You cannot have one compatible in two schemas, so for old bindings (and DTS): 1. Don't convert them, 2. Convert with keeping old properties - as you pointed this might be full of conditionals/allOf, so difficult to maintain and read, 3. Convert dropping old stuff. For the option 3. for sure Rob will ask why. :) > > If we were to start introducing conditionals on existence of child > nodes, and marking the old bindings as deprecated in one large schema, > then that sounds like it would be very messy and hard to read and > maintain. But perhaps there is some way to do this without such > downsides that I'm not aware of. Best regards, Krzysztof