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([2a01:e0a:3cb:7bb0:bd12:acc9:5374:bd9b]) by smtp.gmail.com with ESMTPSA id n189sm8495216wmb.43.2020.06.24.08.44.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Jun 2020 08:44:46 -0700 (PDT) Subject: Re: [Tee-dev] [PATCHv8 1/3] optee: use uuid for sysfs driver entry To: James Bottomley , Sumit Garg Cc: Maxim Uvarov , Greg Kroah-Hartman , Linux Kernel Mailing List , Jarkko Sakkinen , Arnd Bergmann , "tee-dev @ lists . linaro . org" , Jason Gunthorpe , linux-integrity@vger.kernel.org, peterhuewe@gmx.de References: <20200604175851.758-1-maxim.uvarov@linaro.org> <20200604175851.758-2-maxim.uvarov@linaro.org> <1592507935.15159.5.camel@HansenPartnership.com> <1592578844.4369.5.camel@HansenPartnership.com> <1593012069.28403.11.camel@HansenPartnership.com> From: Jerome Forissier Message-ID: <3aa8705a-0342-25ea-00c4-d5370d91ddb4@forissier.org> Date: Wed, 24 Jun 2020 17:44:45 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <1593012069.28403.11.camel@HansenPartnership.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/24/20 5:21 PM, James Bottomley wrote: > On Wed, 2020-06-24 at 16:17 +0530, Sumit Garg wrote: >> Apologies for delay in my reply as I was busy with some other stuff. >> >> On Fri, 19 Jun 2020 at 20:30, James Bottomley >> wrote: > [...] >>> it's about consistency with what the kernel types mean. When some >>> checker detects your using little endian operations on a big endian >>> structure (like in the prink for instance) they're going to keep >>> emailing you about it. >> >> As mentioned above, using different terminology is meant to cause >> more confusion than just difference in endianness which is manageable >> inside TEE. >> >> And I think it's safe to say that the kernel implements UUID in big >> endian format and thus uses %pUb whereas OP-TEE implements UUID in >> little endian format and thus uses %pUl. > > So what I think you're saying is that if we still had uuid_be and > uuid_le you'd use uuid_le, because that's exactly the structure > described in the docs. But because we renamed > > uuid_be -> uuid_t > uuid_le -> guid_t > > You can't use guid_t as a kernel type because it has the wrong name? Let me try to clear the confusion that I introduce myself I believe :-/ IMO: - optee_register_device(const uuid_t *device_uuid) *is* the correct prototype. - device_uuid is *guaranteed* to be BE because OP-TEE makes this guarantee (it converts from its internal LE representation to BE when enumerating the devices, but it doesn't matter to the kernel). - Therefore %pUb is the correct format. I'm sorry for doubting the BE order initially. I am so used to OP-TEE using LE internally, that I missed the fact that we have an explicit conversion... Does this sound good? Thanks, -- Jerome