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([2a02:3033:6d8:15d8:ec15:f5ad:b85f:a3b8]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45d9ec39ff1sm46305257f8f.10.2026.05.19.00.07.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 19 May 2026 00:07:04 -0700 (PDT) Message-ID: <233a93d1-1901-440b-902b-f0e482d9a1a4@gmail.com> Date: Tue, 19 May 2026 09:07:01 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] iio: dac: Add AD5529R DAC driver support To: Jonathan Cameron , Janani Sunil Cc: Lars-Peter Clausen , Michael Hennerich , David Lechner , =?UTF-8?Q?Nuno_S=C3=A1?= , Andy Shevchenko , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Philipp Zabel , Jonathan Corbet , Shuah Khan , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org References: <20260508-ad5529r-driver-v2-0-e315441685d7@analog.com> <20260508-ad5529r-driver-v2-2-e315441685d7@analog.com> <20260508143017.28f86551@jic23-huawei> Content-Language: en-US From: Janani Sunil In-Reply-To: <20260508143017.28f86551@jic23-huawei> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 5/8/26 15:30, Jonathan Cameron wrote: > On Fri, 8 May 2026 13:55:48 +0200 > Janani Sunil wrote: > >> Add support for AD5529R 16-channel, 12/16 bit Digital to Analog Converter >> >> Signed-off-by: Janani Sunil >> +/* Register Map */ >> +#define AD5529R_REG_INTERFACE_CONFIG_A 0x00 >> +#define AD5529R_REG_INTERFACE_CONFIG_B 0x01 >> +#define AD5529R_REG_DEVICE_CONFIG 0x02 >> +#define AD5529R_REG_CHIP_TYPE 0x03 >> +#define AD5529R_REG_PRODUCT_ID_L 0x04 >> +#define AD5529R_REG_PRODUCT_ID_H 0x05 >> +#define AD5529R_REG_CHIP_GRADE 0x06 >> +#define AD5529R_REG_SCRATCH_PAD 0x0A >> +#define AD5529R_REG_SPI_REVISION 0x0B >> +#define AD5529R_REG_VENDOR_L 0x0C >> +#define AD5529R_REG_VENDOR_H 0x0D >> +#define AD5529R_REG_STREAM_MODE 0x0E >> +#define AD5529R_REG_TRANSFER_CONFIG 0x0F >> +#define AD5529R_REG_INTERFACE_CONFIG_C 0x10 >> +#define AD5529R_REG_INTERFACE_STATUS_A 0x11 >> + >> +/* Configuration registers */ >> +#define AD5529R_REG_MULTI_DAC_CH_SEL (0x14 + 1) > Feels like this would all be simpler if you used autoincrement rather than > default value of autdecrement. What breaks if you do that? > Superficially feels like all the +1 would go away - though with need > for a byte swap? Might be worth that pain for the simpler code. > Should just be a regmap_config parameter. Switching to auto increment is feasible. I'll switch to auto increment and eliminate all the +1 offsets. >> + >> +static const struct regmap_range ad5529r_8bit_readable_ranges[] = { >> + regmap_reg_range(AD5529R_REG_INTERFACE_CONFIG_A, AD5529R_REG_CHIP_GRADE), >> + regmap_reg_range(AD5529R_REG_SCRATCH_PAD, AD5529R_REG_VENDOR_H), >> + regmap_reg_range(AD5529R_REG_STREAM_MODE, AD5529R_REG_INTERFACE_STATUS_A), >> +}; >> + >> +static const struct regmap_range ad5529r_16bit_readable_ranges[] = { > Tricky bit here is you are saying it's a 16 bit regmap but then providing > address ranges including the ones we shouldn't use. We need to hide those > intermediate addresses. Various things might work depending on the addresses. > Can we hide the bottom bit of each address then write it to appropriate value > under the hood. That is divide addresses by 2? I'll address this by using reg_stride = 2 in the 16-bit regmap configuration, which automatically handles the address spacing and eliminates the need for manual address range exclusion. >> + int ret; >> + >> + switch (mask) { >> + case IIO_CHAN_INFO_RAW: >> + reg_addr = AD5529R_REG_DAC_INPUT_A(chan->channel); >> + ret = regmap_read(st->regmap_16bit, reg_addr, ®_val_h); >> + if (ret) >> + return ret; >> + >> + *val = reg_val_h; >> + >> + return IIO_VAL_INT; >> + case IIO_CHAN_INFO_SCALE: >> + /* >> + * Using default 0-5V range: VOUTn = A × D/2^N + B >> + * where A = 5V, B = 0V, D = digital code, N = resolution >> + * Scale = 5000mV / 2^resolution > See the comment on the dt-binding. I think we need support for > dt described output ranges from the start. This is a rare multi range > device where we could set a safe default but to me it makes little sense > and the driver will be doing something unexpected if a newer DT is > provided with a different range. I will add devicetree properties for per channel output range configuration. >> + >> +static int ad5529r_probe(struct spi_device *spi) >> +{ >> + struct device *dev = &spi->dev; >> + struct iio_dev *indio_dev; >> + struct ad5529r_state *st; >> + int ret; >> + >> + indio_dev = devm_iio_device_alloc(dev, sizeof(*st)); >> + if (!indio_dev) >> + return -ENOMEM; >> + >> + st = iio_priv(indio_dev); >> + >> + st->spi = spi; >> + >> + ret = devm_regulator_bulk_get_enable(dev, AD5529R_NUM_SUPPLIES, >> + ad5529r_supply_names); >> + if (ret) >> + return dev_err_probe(dev, ret, "Failed to get and enable regulators\n"); >> + >> + st->regmap_8bit = devm_regmap_init_spi(spi, &ad5529r_regmap_8bit_config); >> + if (IS_ERR(st->regmap_8bit)) >> + return dev_err_probe(dev, PTR_ERR(st->regmap_8bit), >> + "Failed to initialize 8-bit regmap\n"); >> + >> + st->regmap_16bit = devm_regmap_init_spi(spi, &ad5529r_regmap_16bit_config); >> + if (IS_ERR(st->regmap_16bit)) >> + return dev_err_probe(dev, PTR_ERR(st->regmap_16bit), >> + "Failed to initialize 16-bit regmap\n"); >> + >> + ret = ad5529r_reset(st); >> + if (ret) >> + return dev_err_probe(dev, ret, "Failed to reset device\n"); >> + >> + ret = ad5529r_detect_device(st); >> + if (ret) >> + return dev_err_probe(dev, ret, "Failed to detect device variant\n"); > No to this. It breaks the use of fallback device tree compatibles. As such we > never fail on an ID missmatch. Instead we just believe firmware when it says > whatever is there is compatible with this device. See below on why I think > we need to break this into separate compatibles. I'll create separate compatibles and remove the device ID detection logic. Best Regards, Janani Sunil