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From:   Tim Harvey <tharvey@gateworks.com>
Date:   Wed, 28 Feb 2018 13:44:36 -0800
Message-ID: <CAJ+vNU3U85mwv9_U5O5Xq3o=D7k_63Dwy4xf+bbLiink7pyapQ@mail.gmail.com>
Subject: Re: [RFC 3/4] hwmon: add Gateworks System Controller support
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     Lee Jones <lee.jones@linaro.org>, Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Mark Brown <broonie@kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, linux-hwmon@vger.kernel.org,
        linux-input@vger.kernel.org
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Sender: linux-kernel-owner@vger.kernel.org
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On Tue, Feb 27, 2018 at 6:05 PM, Guenter Roeck <linux@roeck-us.net> wrote:
> On 02/27/2018 05:21 PM, Tim Harvey wrote:
>>
>> The Gateworks System Controller has a hwmon sub-component that exposes
>> up to 16 ADC's, some of which are temperature sensors, others which are
>> voltage inputs. The ADC configuration (register mapping and name) is
>> configured via device-tree and varies board to board.
>>
>> Signed-off-by: Tim Harvey <tharvey@gateworks.com>
>> ---
>>   drivers/hwmon/Kconfig     |   6 +
>>   drivers/hwmon/Makefile    |   1 +
>>   drivers/hwmon/gsc-hwmon.c | 299
>> ++++++++++++++++++++++++++++++++++++++++++++++
>>   3 files changed, 306 insertions(+)
>>   create mode 100644 drivers/hwmon/gsc-hwmon.c
>>
>> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
>> index 7ad0176..9cdc3cb 100644
>> --- a/drivers/hwmon/Kconfig
>> +++ b/drivers/hwmon/Kconfig
>> @@ -475,6 +475,12 @@ config SENSORS_F75375S
>>           This driver can also be built as a module.  If so, the module
>>           will be called f75375s.
>>   +config SENSORS_GSC
>> +        tristate "Gateworks System Controller ADC"
>> +        depends on MFD_GSC
>> +        help
>> +          Support for the Gateworks System Controller A/D converters.
>> +
>>   config SENSORS_MC13783_ADC
>>           tristate "Freescale MC13783/MC13892 ADC"
>>           depends on MFD_MC13XXX
>> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
>> index 0fe489f..835a536 100644
>> --- a/drivers/hwmon/Makefile
>> +++ b/drivers/hwmon/Makefile
>> @@ -69,6 +69,7 @@ obj-$(CONFIG_SENSORS_G760A)   += g760a.o
>>   obj-$(CONFIG_SENSORS_G762)    += g762.o
>>   obj-$(CONFIG_SENSORS_GL518SM) += gl518sm.o
>>   obj-$(CONFIG_SENSORS_GL520SM) += gl520sm.o
>> +obj-$(CONFIG_SENSORS_GSC)      += gsc-hwmon.o
>>   obj-$(CONFIG_SENSORS_GPIO_FAN)        += gpio-fan.o
>>   obj-$(CONFIG_SENSORS_HIH6130) += hih6130.o
>>   obj-$(CONFIG_SENSORS_ULTRA45) += ultra45_env.o
>> diff --git a/drivers/hwmon/gsc-hwmon.c b/drivers/hwmon/gsc-hwmon.c
>> new file mode 100644
>> index 0000000..3e14bea
>> --- /dev/null
>> +++ b/drivers/hwmon/gsc-hwmon.c
>> @@ -0,0 +1,299 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) 2018 Gateworks Corporation
>> + */
>> +#define DEBUG

Guenter,

Thanks for the review!

>
>
> Please no.

oops - left that in by mistake.

>
>> +
>> +#include <linux/hwmon.h>
>> +#include <linux/hwmon-sysfs.h>
>> +#include <linux/mfd/gsc.h>
>> +#include <linux/module.h>
>> +#include <linux/of.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/regmap.h>
>> +#include <linux/slab.h>
>> +
>> +/* map channel to channel info */
>> +struct gsc_hwmon_ch {
>> +       u8 reg;
>> +       char name[32];
>> +};
>> +static struct gsc_hwmon_ch gsc_temp_ch[16];
>
>
> 16 temperature channels ...

It has 16x ADC channels where some can be temperatures and others can
be voltage inputs (based on device tree).

>
>
>> +static struct gsc_hwmon_ch gsc_in_ch[16];
>> +static struct gsc_hwmon_ch gsc_fan_ch[5];
>> +
>> +static int
>> +gsc_hwmon_read(struct device *dev, enum hwmon_sensor_types type, u32
>> attr,
>> +              int ch, long *val)
>> +{
>> +       struct gsc_dev *gsc = dev_get_drvdata(dev);
>> +       int sz, ret;
>> +       u8 reg;
>> +       u8 buf[3];
>> +
>> +       dev_dbg(dev, "%s type=%d attr=%d ch=%d\n", __func__, type, attr,
>> ch);
>> +       switch (type) {
>> +       case hwmon_in:
>> +               sz = 3;
>> +               reg = gsc_in_ch[ch].reg;
>> +               break;
>> +       case hwmon_temp:
>> +               sz = 2;
>> +               reg = gsc_temp_ch[ch].reg;
>> +               break;
>> +       default:
>> +               return -EOPNOTSUPP;
>> +       }
>> +
>> +       ret = regmap_bulk_read(gsc->regmap_hwmon, reg, &buf, sz);
>> +       if (!ret) {
>> +               *val = 0;
>> +               while (sz-- > 0)
>> +                       *val |= (buf[sz] << (8*sz));
>> +               if ((type == hwmon_temp) && *val > 0x8000)
>
>
> Excessive [and inconsistent] ( )
>
> Please make this
>         if (ret)
>                 return ret;
>         ...
>         return 0;

understood - a much cleaner pattern

>
>
>> +                       *val -= 0xffff;
>> +       }
>> +
>> +       return ret;
>> +}
>> +
>> +static int
>> +gsc_hwmon_read_string(struct device *dev, enum hwmon_sensor_types type,
>> +                     u32 attr, int ch, const char **buf)
>> +{
>> +       dev_dbg(dev, "%s type=%d attr=%d ch=%d\n", __func__, type, attr,
>> ch);
>> +       switch (type) {
>> +       case hwmon_in:
>> +       case hwmon_temp:
>> +       case hwmon_fan:
>> +               switch (attr) {
>> +               case hwmon_in_label:
>> +                       *buf = gsc_in_ch[ch].name;
>> +                       return 0;
>> +                       break;
>> +               case hwmon_temp_label:
>> +                       *buf = gsc_temp_ch[ch].name;
>> +                       return 0;
>> +                       break;
>> +               case hwmon_fan_label:
>> +                       *buf = gsc_fan_ch[ch].name;
>> +                       return 0;
>> +                       break;
>
>
> return followed by break doesn't make sense.

right - removed

>
>
>> +               default:
>> +                       break;
>> +               }
>> +               break;
>> +       default:
>> +               break;
>> +       }
>> +
>> +       return -ENOTSUPP;
>> +}
>> +
>> +static int
>> +gsc_hwmon_write(struct device *dev, enum hwmon_sensor_types type, u32
>> attr,
>> +              int ch, long val)
>> +{
>> +       struct gsc_dev *gsc = dev_get_drvdata(dev);
>> +       int ret;
>> +       u8 reg;
>> +       u8 buf[3];
>> +
>> +       dev_dbg(dev, "%s type=%d attr=%d ch=%d\n", __func__, type, attr,
>> ch);
>> +       switch (type) {
>> +       case hwmon_fan:
>> +               buf[0] = val & 0xff;
>> +               buf[1] = (val >> 8) & 0xff;
>> +               reg = gsc_fan_ch[ch].reg;
>> +               ret = regmap_bulk_write(gsc->regmap_hwmon, reg, &buf, 2);
>
>
>         &buf -> buf

yikes - thanks for catching that

>
>> +               break;
>> +       default:
>> +               ret = -EOPNOTSUPP;
>> +               break;
>> +       }
>> +
>> +       return ret;
>> +}
>> +
>> +static umode_t
>> +gsc_hwmon_is_visible(const void *_data, enum hwmon_sensor_types type, u32
>> attr,
>> +                    int ch)
>> +{
>> +       const struct gsc_dev *gsc = _data;
>> +       struct device *dev = gsc->dev;
>> +       umode_t mode = 0;
>> +
>> +       switch (type) {
>> +       case hwmon_fan:
>> +               if (attr == hwmon_fan_input)
>> +                       mode = (S_IRUGO | S_IWUSR);
>
>
> Unnecessary ( )

ok

>
>
>> +               break;
>> +       case hwmon_temp:
>> +       case hwmon_in:
>> +               mode = S_IRUGO;
>> +               break;
>> +       default:
>> +               break;
>> +       }
>> +       dev_dbg(dev, "%s type=%d attr=%d ch=%d mode=0x%x\n", __func__,
>> type,
>> +               attr, ch, mode);
>> +
>> +       return mode;
>> +}
>> +
>> +static u32 gsc_in_config[] = {
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       HWMON_I_INPUT,
>> +       0
>> +};
>> +static const struct hwmon_channel_info gsc_in = {
>> +       .type = hwmon_in,
>> +       .config = gsc_in_config,
>> +};
>> +
>> +static u32 gsc_temp_config[] = {
>> +       HWMON_T_INPUT,
>> +       HWMON_T_INPUT,
>> +       HWMON_T_INPUT,
>> +       HWMON_T_INPUT,
>> +       HWMON_T_INPUT,
>> +       HWMON_T_INPUT,
>> +       HWMON_T_INPUT,
>> +       HWMON_T_INPUT,
>> +       0
>
>
> ... but this array only has 8+1 elements. This seems inconsistent.
> How about using some defines for array sizes ?
>
> Also, why initialize those arrays ? You are overwriting them below.
> You could just use a static size array instead.
>
> I assume it is guaranteed that there is only exactly one instance
> of this device in the system. Have you tried what happens if you
> declare two instances anyway ? The result must be interesting,
> with all those static variables.

yes, that static arrays are not very forward-thinking and yes my
arrays are not consistent. I'll convert to dynamically allocating the
channels for v2

>
>> +};
>> +static const struct hwmon_channel_info gsc_temp = {
>> +       .type = hwmon_temp,
>> +       .config = gsc_temp_config,
>> +};
>> +
>> +static u32 gsc_fan_config[] = {
>> +       HWMON_F_INPUT,
>> +       HWMON_F_INPUT,
>> +       HWMON_F_INPUT,
>> +       HWMON_F_INPUT,
>> +       HWMON_F_INPUT,
>> +       HWMON_F_INPUT,
>> +       0,
>> +};
>
>
> The matching gsc_fan_ch has only 5 entries.

right - certainly an issue

>
>
>> +static const struct hwmon_channel_info gsc_fan = {
>> +       .type = hwmon_fan,
>> +       .config = gsc_fan_config,
>> +};
>> +
>> +static const struct hwmon_channel_info *gsc_info[] = {
>> +       &gsc_temp,
>> +       &gsc_in,
>> +       &gsc_fan,
>> +       NULL
>> +};
>> +
>> +static const struct hwmon_ops gsc_hwmon_ops = {
>> +       .is_visible = gsc_hwmon_is_visible,
>> +       .read = gsc_hwmon_read,
>> +       .read_string = gsc_hwmon_read_string,
>> +       .write = gsc_hwmon_write,
>> +};
>> +
>> +static const struct hwmon_chip_info gsc_chip_info = {
>> +       .ops = &gsc_hwmon_ops,
>> +       .info = gsc_info,
>> +};
>> +
>> +static int gsc_hwmon_probe(struct platform_device *pdev)
>> +{
>> +       struct gsc_dev *gsc = dev_get_drvdata(pdev->dev.parent);
>> +       struct device_node *np;
>> +       struct device *hwmon;
>> +       int temp_count = 0;
>> +       int in_count = 0;
>> +       int fan_count = 0;
>> +       int ret;
>> +
>> +       dev_dbg(&pdev->dev, "%s\n", __func__);
>
>
> You declare local 'dev' variables all over the place, except here,
> where it would actually be used multiple times.
>
> Please either declare one here as well, or drop all the others.

will do

>
>> +       np = of_get_next_child(pdev->dev.of_node, NULL);
>> +       while (np) {
>> +               u32 reg, type;
>> +               const char *label;
>> +
>> +               of_property_read_u32(np, "reg", &reg);
>> +               of_property_read_u32(np, "type", &type);
>> +               label = of_get_property(np, "label", NULL);
>
>
> It must be interesting to see what happens if no 'label' property
> is provided. Have you tried ? Also, no validation of 'reg' and 'type' ?
> Are you sure ?

will add validation

>
>> +               switch(type) {
>> +               case 0: /* temperature sensor */
>> +                       gsc_temp_config[temp_count] = HWMON_T_INPUT |
>> +                                                     HWMON_T_LABEL;
>> +                       gsc_temp_ch[temp_count].reg = reg;
>> +                       strncpy(gsc_temp_ch[temp_count].name, label, 32);
>
>
> This leaves the string unterminated if it is too long. Have you tested
> what happens in this situation ? Consider using strlcpy instead.
>
> Also please use sizeof() instead of '32'.

ok

>
>> +                       if (temp_count < ARRAY_SIZE(gsc_temp_config))
>> +                               temp_count++;
>
>
> I would suggest to abort with EINVAL if this happens. Otherwise the last
> entry
> is overwritten, which doesn't make much sense. Also, this accepts up to
> ARRAY_SIZE()
> entries, leaving no termination.
>
>> +                       break;
>> +               case 1: /* voltage sensor */
>> +                       gsc_in_config[in_count] = HWMON_I_INPUT |
>> +                                                 HWMON_I_LABEL;
>> +                       gsc_in_ch[in_count].reg = reg;
>
>
> So a reg value of 0xXXyy is auto-converted to 0xYY ?

Do you mean stuffing a u32 into a u8?

>
>> +                       strncpy(gsc_in_ch[in_count].name, label, 32);
>> +                       if (in_count < ARRAY_SIZE(gsc_in_config))
>> +                               in_count++;
>> +                       break;
>> +               case 2: /* fan controller setpoint */
>> +                       gsc_fan_config[fan_count] = HWMON_F_INPUT |
>> +                                                   HWMON_F_LABEL;
>> +                       gsc_fan_ch[fan_count].reg = reg;
>
>
> It is going to be interesting to see what happens if there are more than
> 5 such entries.

will fix

>
>> +                       strncpy(gsc_fan_ch[fan_count].name, label, 32);
>> +                       if (fan_count < ARRAY_SIZE(gsc_fan_config))
>> +                               fan_count++;
>> +                       break;
>
>
> All other types are silently ignored ?

will fix

>
>> +               }
>> +               np = of_get_next_child(pdev->dev.of_node, np);
>> +       }
>> +       /* terminate list */
>> +       gsc_in_config[in_count] = 0;
>> +       gsc_temp_config[temp_count] = 0;
>> +       gsc_fan_config[fan_count] = 0;
>> +
>
> I would suggest to move above code into a separate function.

will do

>
>> +       hwmon = devm_hwmon_device_register_with_info(&pdev->dev,
>> +                                                    KBUILD_MODNAME, gsc,
>> +                                                    &gsc_chip_info,
>> NULL);
>> +       if (IS_ERR(hwmon)) {
>> +               ret = PTR_ERR(hwmon);
>> +               dev_err(&pdev->dev, "Unable to register hwmon device:
>> %d\n",
>> +                       ret);
>> +               return ret;
>> +       }
>
>
> The error would be ENOMEM. Is it necessary to report that again ?

could also return -EINVAL but not with the args I'm passing in so I'll
change it to:
return PTR_ERR_OR_ZERO(hwmon);

Thanks!

Tim