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Date: Mon, 23 Nov 2020 11:03:09 -0800
From: Tao Ren <rentao.bupt@...il.com>
To: Guenter Roeck <linux@...ck-us.net>
Cc: Jean Delvare <jdelvare@...e.com>, Jonathan Corbet <corbet@....net>,
linux-hwmon@...r.kernel.org, linux-doc@...r.kernel.org,
linux-kernel@...r.kernel.org, openbmc@...ts.ozlabs.org,
taoren@...com, mikechoi@...com
Subject: Re: [PATCH v4 1/2] hwmon: (max127) Add Maxim MAX127 hardware
monitoring driver
On Mon, Nov 23, 2020 at 05:18:32AM -0800, Guenter Roeck wrote:
> On Sun, Nov 22, 2020 at 11:45:31PM -0800, rentao.bupt@...il.com wrote:
> > From: Tao Ren <rentao.bupt@...il.com>
> >
> > Add hardware monitoring driver for the Maxim MAX127 chip.
> >
> > MAX127 min/max range handling code is inspired by the max197 driver.
> >
> > Signed-off-by: Tao Ren <rentao.bupt@...il.com>
> > ---
> > Changes in v4:
> > - delete unnecessary "#include" lines.
> > - simplify i2c_transfer() error handling.
> > - add mutex to protect ctrl_byte in write_min|max() functions.
> > Changes in v3:
> > - no code change. xdp maintainers were removed from to/cc list.
> > Changes in v2:
> > - replace devm_hwmon_device_register_with_groups() with
> > devm_hwmon_device_register_with_info() API.
> > - divide min/max read and write methods to separate functions.
> > - fix raw-to-vin conversion logic.
> > - refine ctrl_byte handling so mutex is not needed to protect the
> > byte.
> > - improve i2c_transfer() error handling.
> > - a few other improvements (comments, variable naming, and etc.).
> >
> > drivers/hwmon/Kconfig | 9 ++
> > drivers/hwmon/Makefile | 1 +
> > drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 356 insertions(+)
> > create mode 100644 drivers/hwmon/max127.c
> >
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 9d600e0c5584..716df51edc87 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> > This driver can also be built as a module. If so, the module
> > will be called max1111.
> >
> > +config SENSORS_MAX127
> > + tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> > + depends on I2C
> > + help
> > + Say y here to support Maxim's MAX127 DAS chips.
> > +
> > + This driver can also be built as a module. If so, the module
> > + will be called max127.
> > +
> > config SENSORS_MAX16065
> > tristate "Maxim MAX16065 System Manager and compatibles"
> > depends on I2C
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index 1083bbfac779..01ca5d3fbad4 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260) += ltc4260.o
> > obj-$(CONFIG_SENSORS_LTC4261) += ltc4261.o
> > obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> > obj-$(CONFIG_SENSORS_MAX1111) += max1111.o
> > +obj-$(CONFIG_SENSORS_MAX127) += max127.o
> > obj-$(CONFIG_SENSORS_MAX16065) += max16065.o
> > obj-$(CONFIG_SENSORS_MAX1619) += max1619.o
> > obj-$(CONFIG_SENSORS_MAX1668) += max1668.o
> > diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> > new file mode 100644
> > index 000000000000..1c54146b6086
> > --- /dev/null
> > +++ b/drivers/hwmon/max127.c
> > @@ -0,0 +1,346 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Hardware monitoring driver for MAX127.
> > + *
> > + * Copyright (c) 2020 Facebook Inc.
> > + */
> > +
> > +#include <linux/err.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/i2c.h>
> > +#include <linux/init.h>
> > +#include <linux/module.h>
> > +
> > +/*
> > + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> > + * Format" for details.
> > + */
> > +#define MAX127_CTRL_START BIT(7)
> > +#define MAX127_CTRL_SEL_SHIFT 4
> > +#define MAX127_CTRL_RNG BIT(3)
> > +#define MAX127_CTRL_BIP BIT(2)
> > +#define MAX127_CTRL_PD1 BIT(1)
> > +#define MAX127_CTRL_PD0 BIT(0)
> > +
> > +#define MAX127_NUM_CHANNELS 8
> > +#define MAX127_SET_CHANNEL(ch) (((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> > +
> > +/*
> > + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> > + * and Polarity Selection" for details.
> > + */
> > +#define MAX127_FULL_RANGE 10000 /* 10V */
> > +#define MAX127_HALF_RANGE 5000 /* 5V */
> > +
> > +/*
> > + * MAX127 returns 2 bytes at read:
> > + * - the first byte contains data[11:4].
> > + * - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> > + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> > + * for details.
> > + */
> > +#define MAX127_DATA_LEN 2
> > +#define MAX127_DATA_SHIFT 4
> > +
> > +#define MAX127_SIGN_BIT BIT(11)
> > +
> > +struct max127_data {
> > + struct mutex lock;
> > + struct i2c_client *client;
> > + u8 ctrl_byte[MAX127_NUM_CHANNELS];
> > +};
> > +
> > +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> > +{
> > + int status;
> > + struct i2c_msg msg = {
> > + .addr = client->addr,
> > + .flags = 0,
> > + .len = sizeof(ctrl_byte),
> > + .buf = &ctrl_byte,
> > + };
> > +
> > + status = i2c_transfer(client->adapter, &msg, 1);
> > +
> > + return (status == 1) ? 0 : -EIO;
>
> This isn't what I said and asked for. It drops the unnecessary else,
> but now it overwrites an error value.
>
> Guenter
>
> > +}
> > +
> > +static int max127_read_channel(struct i2c_client *client, long *val)
> > +{
> > + int status;
> > + u8 i2c_data[MAX127_DATA_LEN];
> > + struct i2c_msg msg = {
> > + .addr = client->addr,
> > + .flags = I2C_M_RD,
> > + .len = sizeof(i2c_data),
> > + .buf = i2c_data,
> > + };
> > +
> > + status = i2c_transfer(client->adapter, &msg, 1);
> > + if (status != 1)
> > + return -EIO;
>
> This isn't what I asked for.
>
> Guenter
Both places are fixed in v5. Thanks for the clarify, Guenter.
Cheers,
Tao
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