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([115.96.68.45]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b24268e7f5sm42266995ad.35.2026.03.29.00.34.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 29 Mar 2026 00:34:19 -0700 (PDT) From: Tabrez Ahmed To: linux@roeck-us.net Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, shuah@kernel.org, me@brighamcampbell.com, Tabrez Ahmed Subject: [PATCH v2 1/2] hwmon: (ads7871) Convert to hwmon_device_register_with_info Date: Sun, 29 Mar 2026 13:03:51 +0530 Message-ID: <20260329073352.270451-2-tabreztalks@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260329073352.270451-1-tabreztalks@gmail.com> References: <20260329073352.270451-1-tabreztalks@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Convert the ads7871 driver from the legacy hwmon_device_register() to the modern hwmon_device_register_with_info() API. This migration simplifies the driver by using the structured hwmon_channel_info approach and prepares the codebase for the transition to a shared DMA-safe buffer. Signed-off-by: Tabrez Ahmed --- drivers/hwmon/ads7871.c | 76 ++++++++++++++++++++++------------------- 1 file changed, 41 insertions(+), 35 deletions(-) diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c index 9bfdf9e6bcd77..41a1e9bbd4050 100644 --- a/drivers/hwmon/ads7871.c +++ b/drivers/hwmon/ads7871.c @@ -56,7 +56,6 @@ #include #include #include -#include #include #include =20 @@ -65,10 +64,20 @@ struct ads7871_data { struct spi_device *spi; }; +static umode_t ads7871_is_visible(const void *data, + enum hwmon_sensor_types type, + u32 attr, int channel) +{ + if (type =3D=3D hwmon_in && attr =3D=3D hwmon_in_input) + return 0444; + + return 0; +} =20 static int ads7871_read_reg8(struct spi_device *spi, int reg) { int ret; + reg =3D reg | INST_READ_BM; ret =3D spi_w8r8(spi, reg); return ret; @@ -77,6 +86,7 @@ static int ads7871_read_reg8(struct spi_device *spi, int = reg) static int ads7871_read_reg16(struct spi_device *spi, int reg) { int ret; + reg =3D reg | INST_READ_BM | INST_16BIT_BM; ret =3D spi_w8r16(spi, reg); return ret; @@ -85,19 +95,20 @@ static int ads7871_read_reg16(struct spi_device *spi, i= nt reg) static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val) { u8 tmp[2] =3D {reg, val}; + return spi_write(spi, tmp, sizeof(tmp)); } =20 -static ssize_t voltage_show(struct device *dev, struct device_attribute *d= a, - char *buf) +static int ads7871_read(struct device *dev, enum hwmon_sensor_types type, + u32 attr, int channel, long *val) { struct ads7871_data *pdata =3D dev_get_drvdata(dev); struct spi_device *spi =3D pdata->spi; - struct sensor_device_attribute *attr =3D to_sensor_dev_attr(da); - int ret, val, i =3D 0; - uint8_t channel, mux_cnv; + int ret, raw_val, i =3D 0; + uint8_t mux_cnv; =20 - channel =3D attr->index; + if (type !=3D hwmon_in || attr !=3D hwmon_in_input) + return -EOPNOTSUPP; /* * TODO: add support for conversions * other than single ended with a gain of 1 @@ -127,39 +138,34 @@ static ssize_t voltage_show(struct device *dev, struc= t device_attribute *da, } =20 if (mux_cnv =3D=3D 0) { - val =3D ads7871_read_reg16(spi, REG_LS_BYTE); - if (val < 0) - return val; + raw_val =3D ads7871_read_reg16(spi, REG_LS_BYTE); + if (raw_val < 0) + return raw_val; + /*result in volts*10000 =3D (val/8192)*2.5*10000*/ - val =3D ((val >> 2) * 25000) / 8192; - return sysfs_emit(buf, "%d\n", val); + *val =3D ((raw_val >> 2) * 25000) / 8192; + return 0; } =20 return -ETIMEDOUT; } =20 -static SENSOR_DEVICE_ATTR_RO(in0_input, voltage, 0); -static SENSOR_DEVICE_ATTR_RO(in1_input, voltage, 1); -static SENSOR_DEVICE_ATTR_RO(in2_input, voltage, 2); -static SENSOR_DEVICE_ATTR_RO(in3_input, voltage, 3); -static SENSOR_DEVICE_ATTR_RO(in4_input, voltage, 4); -static SENSOR_DEVICE_ATTR_RO(in5_input, voltage, 5); -static SENSOR_DEVICE_ATTR_RO(in6_input, voltage, 6); -static SENSOR_DEVICE_ATTR_RO(in7_input, voltage, 7); - -static struct attribute *ads7871_attrs[] =3D { - &sensor_dev_attr_in0_input.dev_attr.attr, - &sensor_dev_attr_in1_input.dev_attr.attr, - &sensor_dev_attr_in2_input.dev_attr.attr, - &sensor_dev_attr_in3_input.dev_attr.attr, - &sensor_dev_attr_in4_input.dev_attr.attr, - &sensor_dev_attr_in5_input.dev_attr.attr, - &sensor_dev_attr_in6_input.dev_attr.attr, - &sensor_dev_attr_in7_input.dev_attr.attr, +static const struct hwmon_channel_info * const ads7871_info[] =3D { + HWMON_CHANNEL_INFO(in, + HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT, + HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT, HWMON_I_INPUT), NULL }; 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([115.96.68.45]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b24268e7f5sm42266995ad.35.2026.03.29.00.34.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 29 Mar 2026 00:34:25 -0700 (PDT) From: Tabrez Ahmed To: linux@roeck-us.net Cc: linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org, shuah@kernel.org, me@brighamcampbell.com, Tabrez Ahmed Subject: [PATCH v2 2/2] hwmon: (ads7871) Use DMA-safe buffer for SPI writes Date: Sun, 29 Mar 2026 13:03:52 +0530 Message-ID: <20260329073352.270451-3-tabreztalks@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260329073352.270451-1-tabreztalks@gmail.com> References: <20260329073352.270451-1-tabreztalks@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The driver currently passes a stack-allocated buffer to spi_write(), which is incompatible with DMA on systems with CONFIG_VMAP_STACK enabled. Move the transfer buffer into the driver's private data structure to ensure it is DMA-safe. Since this shared buffer now requires serialization, this change depends on the previous commit which migrated the driver to the hwmon 'with_info' API. While moving the logic, also: - Corrected the sign extension for 14-bit data by casting to s16. - Scaled the output to millivolts (2500mV full scale ) to comply with the hwmon ABI. Signed-off-by: Tabrez Ahmed --- drivers/hwmon/ads7871.c | 36 ++++++++++++++++++++++-------------- 1 file changed, 22 insertions(+), 14 deletions(-) diff --git a/drivers/hwmon/ads7871.c b/drivers/hwmon/ads7871.c index 41a1e9bbd4050..cd58c960690f1 100644 --- a/drivers/hwmon/ads7871.c +++ b/drivers/hwmon/ads7871.c @@ -63,6 +63,7 @@ =20 struct ads7871_data { struct spi_device *spi; + u8 tx_buf[2] ____cacheline_aligned; }; static umode_t ads7871_is_visible(const void *data, enum hwmon_sensor_types type, @@ -78,6 +79,7 @@ static int ads7871_read_reg8(struct spi_device *spi, int = reg) { int ret; =20 + reg =3D reg | INST_READ_BM; ret =3D spi_w8r8(spi, reg); return ret; @@ -92,11 +94,12 @@ static int ads7871_read_reg16(struct spi_device *spi, i= nt reg) return ret; } =20 -static int ads7871_write_reg8(struct spi_device *spi, int reg, u8 val) +static int ads7871_write_reg8(struct ads7871_data *pdata, int reg, u8 val) { - u8 tmp[2] =3D {reg, val}; + pdata->tx_buf[0] =3D reg; + pdata->tx_buf[1] =3D val; =20 - return spi_write(spi, tmp, sizeof(tmp)); + return spi_write(pdata->spi, pdata->tx_buf, 2); } =20 static int ads7871_read(struct device *dev, enum hwmon_sensor_types type, @@ -115,7 +118,7 @@ static int ads7871_read(struct device *dev, enum hwmon_= sensor_types type, */ /*MUX_M3_BM forces single ended*/ /*This is also where the gain of the PGA would be set*/ - ret =3D ads7871_write_reg8(spi, REG_GAIN_MUX, + ret =3D ads7871_write_reg8(pdata, REG_GAIN_MUX, (MUX_CNV_BM | MUX_M3_BM | channel)); if (ret < 0) return ret; @@ -123,6 +126,7 @@ static int ads7871_read(struct device *dev, enum hwmon_= sensor_types type, ret =3D ads7871_read_reg8(spi, REG_GAIN_MUX); if (ret < 0) return ret; + mux_cnv =3D ((ret & MUX_CNV_BM) >> MUX_CNV_BV); /* * on 400MHz arm9 platform the conversion @@ -142,8 +146,11 @@ static int ads7871_read(struct device *dev, enum hwmon= _sensor_types type, if (raw_val < 0) return raw_val; =20 - /*result in volts*10000 =3D (val/8192)*2.5*10000*/ - *val =3D ((raw_val >> 2) * 25000) / 8192; + /* + * Use (s16) to ensure the sign bit is preserved during the shift. + * Report millivolts (2.5V =3D 2500mV). + */ + *val =3D ((s16)raw_val >> 2) * 2500 / 8192; return 0; } =20 @@ -180,11 +187,17 @@ static int ads7871_probe(struct spi_device *spi) spi->bits_per_word =3D 8; spi_setup(spi); =20 - ads7871_write_reg8(spi, REG_SER_CONTROL, 0); - ads7871_write_reg8(spi, REG_AD_CONTROL, 0); + pdata =3D devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL); + if (!pdata) + return -ENOMEM; + + pdata->spi =3D spi; + + ads7871_write_reg8(pdata, REG_SER_CONTROL, 0); + ads7871_write_reg8(pdata, REG_AD_CONTROL, 0); =20 val =3D (OSC_OSCR_BM | OSC_OSCE_BM | OSC_REFE_BM | OSC_BUFE_BM); - ads7871_write_reg8(spi, REG_OSC_CONTROL, val); + ads7871_write_reg8(pdata, REG_OSC_CONTROL, val); ret =3D ads7871_read_reg8(spi, REG_OSC_CONTROL); =20 dev_dbg(dev, "REG_OSC_CONTROL write:%x, read:%x\n", val, ret); @@ -195,11 +208,6 @@ static int ads7871_probe(struct spi_device *spi) if (val !=3D ret) return -ENODEV; =20 - pdata =3D devm_kzalloc(dev, sizeof(struct ads7871_data), GFP_KERNEL); - if (!pdata) - return -ENOMEM; - - pdata->spi =3D spi; hwmon_dev =3D devm_hwmon_device_register_with_info(dev, spi->modalias, pdata, &ads7871_chip_info, --=20 2.43.0