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([2a02:810d:15c0:828:bafd:1283:b136:5f6a]) by smtp.gmail.com with ESMTPSA id sb11-20020a170906edcb00b0094f7c1b6a94sm16021020ejb.11.2023.05.02.01.31.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 02 May 2023 01:31:35 -0700 (PDT) Message-ID: <0fbd5236-d923-0a8d-c7cd-c8e814211651@linaro.org> Date: Tue, 2 May 2023 10:31:33 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.1 Subject: Re: [PATCH v3 3/4] dt-bindings: firmware: Add Qualcomm QSEECOM interface To: Maximilian Luz , Rob Herring Cc: Bjorn Andersson , Andy Gross , Konrad Dybcio , Ard Biesheuvel , Krzysztof Kozlowski , Johan Hovold , Sudeep Holla , Ilias Apalodimas , Srinivas Kandagatla , Sumit Garg , Steev Klimaszewski , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org References: <20230305022119.1331495-1-luzmaximilian@gmail.com> <20230305022119.1331495-4-luzmaximilian@gmail.com> <20230308221657.GA3935330-robh@kernel.org> <93657561-d545-7ead-7f6c-dd2c62aab319@gmail.com> Content-Language: en-US From: Krzysztof Kozlowski In-Reply-To: <93657561-d545-7ead-7f6c-dd2c62aab319@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 08/03/2023 23:44, Maximilian Luz wrote: > On 3/8/23 23:16, Rob Herring wrote: >> On Sun, Mar 05, 2023 at 03:21:18AM +0100, Maximilian Luz wrote: >>> Add bindings for the Qualcomm Secure Execution Environment interface >>> (QSEECOM). >> >> Pretty sure I already asked, but no answer in the commit message. Why do >> we need this? You've already declared the platform supports SCM calls >> with "qcom,scm". Why can't you probe whether you have QSEECOM or not? DT >> is for non-discoverable h/w we are stuck with. > > Yes, you've asked this before but I can only repeat what I've written in > my last response to your question: I am not aware of any way to properly > discover the interface at runtime from software. > > If it makes you happy, I can put this in the commit message as well... Yes, please, because commit msg should answer to "why we are doing this", when this is not obvious. If the reviewer asks the same twice it means it is not obvious. > >> Why is software made non-discoverable too? > > Please direct that question at the Qualcomm guys who actually designed > that interface. I can't give you an answer to that, and I'm not all that > happy about this either. > > To reiterate: I've reverse engineered this based on the Windows driver. > The Windows driver loads on an ACPI HID and it doesn't use any function > to check/verify whether the interface is actually present. Adding a DT > entry is the straight-forward adaption to having a HID in ACPI. Best regards, Krzysztof