Re: [PATCH] platform/x86: Add Steam Deck driver

[Andrey Smirnov <andrew.smirnov@gmail.com>]

On Sun, Feb 6, 2022 at 9:51 AM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On 2/5/22 18:20, Andrey Smirnov wrote:
> > Add a driver exposing various bits and pieces of functionality
> > provided by Steam Deck specific VLV0100 device presented by EC
> > firmware. This includes but not limited to:
> >
> >      - CPU/device's fan control
> >      - Read-only access to DDIC registers
> >      - Battery tempreature measurements
> >      - Various display related control knobs
> >      - USB Type-C connector event notification
> >
> > Cc: Hans de Goede <hdegoede@redhat.com>
> > Cc: Mark Gross <markgross@kernel.org>
> > Cc: Jean Delvare <jdelvare@suse.com>
> > Cc: Guenter Roeck <linux@roeck-us.net>
> > Cc: linux-kernel@vger.kernel.org (open list)
> > Cc: platform-driver-x86@vger.kernel.org
> > Cc: linux-hwmon@vger.kernel.org
> > Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
> > ---
> >
> ...
>
>  > +config STEAMDECK
>  > +       tristate "Valve Steam Deck platform driver"
>  > +       depends on X86_64
>  > +       help
>  > +         Driver exposing various bits and pieces of functionality
>  > +     provided by Steam Deck specific VLV0100 device presented by
>  > +     EC firmware. This includes but not limited to:
>
> There seems to be some indentation issue.
>
>  > +         - CPU/device's fan control
>  > +         - Read-only access to DDIC registers
>  > +         - Battery tempreature measurements
>  > +         - Various display related control knobs
>  > +         - USB Type-C connector event notification
>  > +
>  > +     Say N unless you are running on a Steam Deck.
>  > +
>
> This doesn't depend on hwmon, yet it fails if devm_hwmon_device_register_with_info()
> returns an eror. That has a couple of problems: if HWMON=n, it won't compile,
> and if STEAMDECK=y and HWMON=m it won't compile either. You'll have to provide
> some dependency against HWMON to make this work.
>
> ...
>

Yeah, my bad, will fix.

> > +
> > +static int steamdeck_read_fan_speed(struct steamdeck *jup, long *speed)
> > +{
> > +     unsigned long long val;
> > +
> > +     if (ACPI_FAILURE(acpi_evaluate_integer(jup->adev->handle,
> > +                                            "FANR", NULL, &val)))
> > +             return -EIO;
> > +
> > +     *speed = val;
> > +     return 0;
> > +}
> > +
> > +static int
> > +steamdeck_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> > +                  u32 attr, int channel, long *out)
> > +{
> > +     struct steamdeck *sd = dev_get_drvdata(dev);
> > +     unsigned long long val;
> > +
> > +     switch (type) {
> > +     case hwmon_temp:
> > +             if (attr != hwmon_temp_input)
> > +                     return -EOPNOTSUPP;
> > +
> > +             if (ACPI_FAILURE(acpi_evaluate_integer(sd->adev->handle,
> > +                                                    "BATT", NULL, &val)))
> > +                     return -EIO;
> > +             /*
> > +              * Assuming BATT returns deg C we need to mutiply it
> > +              * by 1000 to convert to mC
> > +              */
> > +             *out = val * 1000;
> > +             break;
> > +     case hwmon_fan:
> > +             switch (attr) {
> > +             case hwmon_fan_input:
> > +                     return steamdeck_read_fan_speed(sd, out);
>
> There is a bit of inconsistency here: All other atributes are handled directly,
> except for this one, yet there isn't really a difference in the actual operation.
> Maybe I am missing something. What is the reason for using a function here
> but not for the other attributes ?
>

It is also used to initialize "fan_target" to its initial value in
steamdeck_probe(). There's no ACPI method to read set fan target
speed, so I have to cache it in "fan_target".

> > +             case hwmon_fan_target:
> > +                     *out = sd->fan_target;
> > +                     break;
> > +             case hwmon_fan_fault:
> > +                     if (ACPI_FAILURE(acpi_evaluate_integer(
> > +                                              sd->adev->handle,
> > +                                              "FANC", NULL, &val)))
> > +                             return -EIO;
> > +                     /*
> > +                      * FANC (Fan check):
> > +                      * 0: Abnormal
> > +                      * 1: Normal
> > +                      */
> > +                     *out = !val;
> > +                     break;
> > +             default:
> > +                     return -EOPNOTSUPP;
> > +             }
> > +             break;
> > +     default:
> > +             return -EOPNOTSUPP;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +static int
> > +steamdeck_hwmon_read_string(struct device *dev, enum hwmon_sensor_types type,
> > +                         u32 attr, int channel, const char **str)
> > +{
> > +     switch (type) {
> > +     case hwmon_temp:
> > +             *str = "Battery Temp";
> > +             break;
> > +     case hwmon_fan:
> > +             *str = "System Fan";
> > +             break;
> > +     default:
> > +             return -EOPNOTSUPP;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> > +static int
> > +steamdeck_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
> > +                   u32 attr, int channel, long val)
> > +{
> > +     struct steamdeck *sd = dev_get_drvdata(dev);
> > +
> > +     if (type != hwmon_fan ||
> > +         attr != hwmon_fan_target)
> > +             return -EOPNOTSUPP;
> > +
> > +     if (val > U16_MAX)
> > +             return -EINVAL;
>
> This accepts negative values, and it expects the user to find
> valid ranges. I suggest to use clamp_val() instead.

Will do.