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[92.233.226.227]) by smtp.googlemail.com with ESMTPSA id m14sm1036887ejl.74.2021.09.22.06.03.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Sep 2021 06:03:31 -0700 (PDT) Subject: Re: [PATCH 1/6] dt-bindings: nvmem: add cell-type to nvmem cells To: Ahmad Fatoum , Joakim Zhang , robh+dt@kernel.org, shawnguo@kernel.org, =?UTF-8?Q?Jan_L=c3=bcbbe?= Cc: devicetree@vger.kernel.org, linux-imx@nxp.com, kernel@pengutronix.de, linux-kernel@vger.kernel.org References: <20210908100257.17833-1-qiangqing.zhang@nxp.com> <20210908100257.17833-2-qiangqing.zhang@nxp.com> <6d91d833-08cc-7ce2-4fe5-3d843a8b31ae@pengutronix.de> <181c4037-3c34-0f71-6bb7-a9c11b173064@linaro.org> <8fc0a5e2-18c0-fa81-3eed-a6d596361633@linaro.org> From: Srinivas Kandagatla Message-ID: <53fd9335-baca-fb52-42f1-2af3b08b5f1f@linaro.org> Date: Wed, 22 Sep 2021 14:03:30 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 22/09/2021 13:58, Ahmad Fatoum wrote: > Hi Srini, > > On 22.09.21 14:49, Srinivas Kandagatla wrote: >> >> >> On 22/09/2021 13:31, Ahmad Fatoum wrote: >>>>> >>>>> On 08.09.21 12:02, Joakim Zhang wrote: >>>>>> From: Srinivas Kandagatla >>>>>> >>>>>> Some of the nvmem providers encode data for certain type of nvmem cell, >>>>>> example mac-address is stored in ascii or with delimiter or in reverse order. >>>>>> >>>>>> This is much specific to vendor, so having a cell-type would allow nvmem >>>>>> provider drivers to post-process this before using it. >>>>> I don't agree with this assessment. Users of the OCOTP so far >>>>> used this specific encoding. Bootloaders decode the OCOTP this way, but this >>>>> encoding isn't really an inherent attribute of the OCOTP. A new NXP SoC >>>>> with a different OTP IP will likely use the same format. Users may even >>>>> use the same format on an EEPROM to populate a second off-SoC interface, .. etc. >>>>> >>>> That is okay. >>> How would you go about using this same format on an EEPROM? >> >> Am guessing that by the time there are more users for such formats, those post-processing functions should be converted into some library functions. > > User A wants to reverse bytes in MAC address. User B stores it in ASCII. > Both use the exact same EEPROM. How could this ever work when the > encoding decision is left to the EEPROM driver? User A and B should mention about this encoding information in there NVMEM provider bindings. Based on that specific post-processing should be selected. --srini > >> >> --srini >> >>> >>>>> I'd thus prefer to not make this specific to the OCOTP as all: >>>>> >>>>>     * #define NVMEM_CELL_ENCODING_MAC_ADDRESS_IMX    /* ... */ >> > >