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([2a01:e0a:106d:1080:e3a1:1a65:a394:be54]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a1f2ca3597sm56737215e9.2.2026.10.20.02.18.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 20 Oct 2026 02:18:32 -0700 (PDT) Message-ID: <729d7100-56b5-4826-be86-358e96be2882@linaro.org> Date: Tue, 20 Oct 2026 11:18:31 +0200 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Neil Armstrong Reply-To: Neil Armstrong Subject: Re: [PATCH v3 3/3] iio: adc: add driver for the MAX34417 Four-Channel High Dynamic Range Power Accumulator To: David Laight Cc: Jonathan Cameron , David Lechner , =?UTF-8?Q?Nuno_S=C3=A1?= , Andy Shevchenko , Rob Herring , Krzysztof Kozlowski , Conor Dooley , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-hwmon@vger.kernel.org References: <20261013-topic-sm8x50-iio-max34417-adc-v3-0-d3604ae4a229@linaro.org> <20261013-topic-sm8x50-iio-max34417-adc-v3-3-d3604ae4a229@linaro.org> <20261020101312.47d2eaf0@pumpkin> Content-Language: en-US, fr Autocrypt: addr=neil.armstrong@linaro.org; keydata= xsBNBE1ZBs8BCAD78xVLsXPwV/2qQx2FaO/7mhWL0Qodw8UcQJnkrWmgTFRobtTWxuRx8WWP GTjuhvbleoQ5Cxjr+v+1ARGCH46MxFP5DwauzPekwJUD5QKZlaw/bURTLmS2id5wWi3lqVH4 BVF2WzvGyyeV1o4RTCYDnZ9VLLylJ9bneEaIs/7cjCEbipGGFlfIML3sfqnIvMAxIMZrvcl9 qPV2k+KQ7q+aXavU5W+yLNn7QtXUB530Zlk/d2ETgzQ5FLYYnUDAaRl+8JUTjc0CNOTpCeik 80TZcE6f8M76Xa6yU8VcNko94Ck7iB4vj70q76P/J7kt98hklrr85/3NU3oti3nrIHmHABEB AAHNKk5laWwgQXJtc3Ryb25nIDxuZWlsLmFybXN0cm9uZ0BsaW5hcm8ub3JnPsLAkQQTAQoA OwIbIwULCQgHAwUVCgkICwUWAgMBAAIeAQIXgBYhBInsPQWERiF0UPIoSBaat7Gkz/iuBQJk Q5wSAhkBAAoJEBaat7Gkz/iuyhMIANiD94qDtUTJRfEW6GwXmtKWwl/mvqQtaTtZID2dos04 YqBbshiJbejgVJjy+HODcNUIKBB3PSLaln4ltdsV73SBcwUNdzebfKspAQunCM22Mn6FBIxQ GizsMLcP/0FX4en9NaKGfK6ZdKK6kN1GR9YffMJd2P08EO8mHowmSRe/ExAODhAs9W7XXExw UNCY4pVJyRPpEhv373vvff60bHxc1k/FF9WaPscMt7hlkbFLUs85kHtQAmr8pV5Hy9ezsSRa GzJmiVclkPc2BY592IGBXRDQ38urXeM4nfhhvqA50b/nAEXc6FzqgXqDkEIwR66/Gbp0t3+r yQzpKRyQif3OwE0ETVkGzwEIALyKDN/OGURaHBVzwjgYq+ZtifvekdrSNl8TIDH8g1xicBYp QTbPn6bbSZbdvfeQPNCcD4/EhXZuhQXMcoJsQQQnO4vwVULmPGgtGf8PVc7dxKOeta+qUh6+ SRh3vIcAUFHDT3f/Zdspz+e2E0hPV2hiSvICLk11qO6cyJE13zeNFoeY3ggrKY+IzbFomIZY 4yG6xI99NIPEVE9lNBXBKIlewIyVlkOaYvJWSV+p5gdJXOvScNN1epm5YHmf9aE2ZjnqZGoM Mtsyw18YoX9BqMFInxqYQQ3j/HpVgTSvmo5ea5qQDDUaCsaTf8UeDcwYOtgI8iL4oHcsGtUX oUk33HEAEQEAAcLAXwQYAQIACQUCTVkGzwIbDAAKCRAWmrexpM/4rrXiB/sGbkQ6itMrAIfn M7IbRuiSZS1unlySUVYu3SD6YBYnNi3G5EpbwfBNuT3H8//rVvtOFK4OD8cRYkxXRQmTvqa3 3eDIHu/zr1HMKErm+2SD6PO9umRef8V82o2oaCLvf4WeIssFjwB0b6a12opuRP7yo3E3gTCS KmbUuLv1CtxKQF+fUV1cVaTPMyT25Od+RC1K+iOR0F54oUJvJeq7fUzbn/KdlhA8XPGzwGRy 4zcsPWvwnXgfe5tk680fEKZVwOZKIEuJC3v+/yZpQzDvGYJvbyix0lHnrCzq43WefRHI5XTT QbM0WUIBIcGmq38+OgUsMYu4NzLu7uZFAcmp6h8g Organization: Linaro In-Reply-To: <20261020101312.47d2eaf0@pumpkin> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/20/26 11:13, David Laight wrote: > On Tue, 13 Oct 2026 16:07:13 +0200 > Neil Armstrong wrote: > >> The MAX34417 is a specialized current and voltage monitor used to >> determine power consumption of portable systems. The driver support >> getting the channels voltage, average power and accumulated average >> power and energy over an I2C/SMBUS serial interface. >> >> The MAX34417 datasheet only specified on how to calculate the >> accumulated average power, but with the Sample Per Second rate >> we can easily get accumulated Energy in mJ. >> >> By default the IIO driver only supports single-shot Voltage >> and Power sensing, but the accumulation can be enabled by >> enabling the Energy IIO channel which then enables the >> Continuous Accumulation Mode. >> >> The counter is common to all channels, so when reading a single >> channel we will copy all accumulators to registers, so in order >> to permit reading individual channels we must accumulate the >> other channels in the driver when Continuous Accumulation Mode >> is enabled. >> >> Signed-off-by: Neil Armstrong > ... >> +#define MAX34417_POWER_READ_LENGTH 8 >> +#define MAX34417_POWER_READ_OFFSET 1 > ... >> +static int max34417_read_acc_power(struct max34417_data *max34417, unsigned int address, >> + u64 *acc_power) >> +{ >> + u8 buf[MAX34417_POWER_READ_LENGTH]; >> + int rc; >> + >> + rc = regmap_noinc_read(max34417->regmap, address, &buf, sizeof(buf)); >> + if (rc) >> + return rc; >> + >> + /* Ignore byte0 */ >> + *acc_power = get_unaligned_be56(&buf[MAX34417_POWER_READ_OFFSET]); >> + >> + return 0; >> +} > > I was thinking: > struct { u64 pad:8; val:56 } buf; > then using bswap64(buf.val) >> 8 on LE. > But why not just: > u64 buf; > and be64toh(buf) & (BITULL(56) - 1) Right, I mean all this could work but I would like to keep using something simpler and get_unaligned_be56 matches all this. I don't think the need for performance is enough to use complex ways to get the value. Thanks, Neil > > David