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From:   Guenter Roeck <groeck@google.com>
Date:   Wed, 11 May 2022 09:23:24 -0700
Message-ID: <CABXOdTe1N7iRTVrCZSgQo=dazofWByM_W6EZgWixLj=Z8Xg0ag@mail.gmail.com>
Subject: Re: [PATCH RESEND v11] platform/chrome: Add ChromeOS ACPI device driver
To:     Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc:     Andy Shevchenko <andy.shevchenko@gmail.com>,
        "Rafael J. Wysocki" <rafael@kernel.org>,
        Len Brown <lenb@kernel.org>,
        Hans de Goede <hdegoede@redhat.com>,
        Mark Gross <markgross@kernel.org>,
        Benson Leung <bleung@chromium.org>,
        Enric Balletbo i Serra <eballetbo@gmail.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Collabora Kernel ML <kernel@collabora.com>,
        Guenter Roeck <groeck@chromium.org>,
        Dmitry Torokhov <dtor@chromium.org>,
        Gwendal Grignou <gwendal@chromium.org>, vbendeb@chromium.org,
        Andy Shevchenko <andy@infradead.org>,
        Ayman Bagabas <ayman.bagabas@gmail.com>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        =?UTF-8?Q?Bla=C5=BE_Hrastnik?= <blaz@mxxn.io>,
        Darren Hart <dvhart@infradead.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Jeremy Soller <jeremy@system76.com>,
        Mattias Jacobsson <2pi@mok.nu>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Rajat Jain <rajatja@google.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Platform Driver <platform-driver-x86@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        chrome-platform@lists.linux.dev
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On Wed, May 11, 2022 at 8:59 AM Muhammad Usama Anjum
<usama.anjum@collabora.com> wrote:
>
> Hi Andy,
>
> Thank you for reviewing.
>
> On 5/10/22 2:33 PM, Andy Shevchenko wrote:
> > On Tue, May 10, 2022 at 8:44 AM Muhammad Usama Anjum
> > <usama.anjum@collabora.com> wrote:
> >>
> >> From: Enric Balletbo i Serra <enric.balletbo@collabora.com>
> >>
> >> The x86 Chromebooks have the ChromeOS ACPI device. This driver attaches
> >> to the ChromeOS ACPI device and exports the values reported by ACPI in a
> >> sysfs directory. This data isn't present in ACPI tables when read
> >> through ACPI tools, hence a driver is needed to do it. The driver gets
> >> data from firmware using the ACPI component of the kernel. The ACPI values
> >> are presented in string form (numbers as decimal values) or binary
> >> blobs, and can be accessed as the contents of the appropriate read only
> >> files in the standard ACPI device's sysfs directory tree. This data is
> >> consumed by the ChromeOS user space.
> >
> >> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >> Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
> >> Cc: Hans de Goede <hdegoede@redhat.com>
> >
> > You can use --cc parameter to `git send-email` instead of putting
> > these lines in the commit message.
> >
> > ...
> >
> >> +#define DEV_ATTR(_var, _name)                                  \
> >> +       static struct device_attribute dev_attr_##_var =        \
> >> +               __ATTR(_name, 0444, chromeos_first_level_attr_show, NULL);
> >> +
> >
> > Why not ATTR_RO()?
> It'll not work as attribute name has . in it.
>
> >
> > ...
> >
> >> +#define GPIO_ATTR_GROUP(_group, _name, _num)                                           \
> >> +       static umode_t attr_is_visible_gpio_##_num(struct kobject *kobj,                \
> >> +                                                  struct attribute *attr, int n)       \
> >> +       {                                                                               \
> >> +               if (_num < chromeos_acpi_gpio_groups)                                   \
> >> +                       return attr->mode;                                              \
> >
> >> +               else                                                                    \
> >
> > Redundant.
> We are deciding on run time that how many GPIO attribute groups need to
> be shown. chromeos_acpi_gpio_groups is set at run time. I don't see why
> `else` can be redundant here.
>

else after return is _always_ unnecessary (and results in static
analyzer messages).

> >
> >> +                       return 0;                                                       \
> >> +       }                                                                               \
> >> +       static ssize_t chromeos_attr_show_gpio_##_num(struct device *dev,               \
> >> +                                                     struct device_attribute *attr,    \
> >> +                                                     char *buf)                        \
> >> +       {                                                                               \
> >> +               char name[ACPI_ATTR_NAME_LEN + 1];                                      \
> >> +               int ret, num;                                                           \
> >> +                                                                                       \
> >> +               ret = parse_attr_name(attr->attr.name, name, &num);                     \
> >> +               if (ret)                                                                \
> >> +                       return ret;                                                     \
> >
> >> +               ret = chromeos_acpi_evaluate_method(dev, _num, num, name, buf);         \
> >> +               if (ret < 0)                                                            \
> >> +                       ret = 0;                                                        \
> >
> > Below I saw the same code, why is the error ignored?
> >
> I'll return the error in both places.
>
> >> +               return ret;                                                             \
> >> +       }                                                                               \
> >> +       static struct device_attribute dev_attr_0_##_group =                            \
> >> +               __ATTR(GPIO.0, 0444, chromeos_attr_show_gpio_##_num, NULL);             \
> >> +       static struct device_attribute dev_attr_1_##_group =                            \
> >> +               __ATTR(GPIO.1, 0444, chromeos_attr_show_gpio_##_num, NULL);             \
> >> +       static struct device_attribute dev_attr_2_##_group =                            \
> >> +               __ATTR(GPIO.2, 0444, chromeos_attr_show_gpio_##_num, NULL);             \
> >> +       static struct device_attribute dev_attr_3_##_group =                            \
> >> +               __ATTR(GPIO.3, 0444, chromeos_attr_show_gpio_##_num, NULL);             \
> >> +                                                                                       \
> >> +       static struct attribute *attrs_##_group[] = {                                   \
> >> +               &dev_attr_0_##_group.attr,                                              \
> >> +               &dev_attr_1_##_group.attr,                                              \
> >> +               &dev_attr_2_##_group.attr,                                              \
> >> +               &dev_attr_3_##_group.attr,                                              \
> >> +               NULL                                                                    \
> >> +       };                                                                              \
> >> +       static const struct attribute_group attr_group_##_group = {                     \
> >> +               .name = _name,                                                          \
> >> +               .is_visible = attr_is_visible_gpio_##_num,                              \
> >
> >> +               .attrs = attrs_##_group                                                 \
> >
> > Keep a comma here.
> Is there any particular reason for it? If there is, I'll add commas to
> all the structures.
> ...
> >
> > ...
> >
> >> +static int parse_attr_name(const char *name, char *attr_name, int *attr_num)
> >> +{
> >> +       int ret = 0;
> >> +
> >> +       strscpy(attr_name, name, ACPI_ATTR_NAME_LEN + 1);
> >> +
> >> +       if (strlen(name) > ACPI_ATTR_NAME_LEN)
> >
> > This seems strange, esp. taking into account that strscpy() returns that.
> >
> > int ret;
> >
> > ret = strscpy(...);
> > if (ret == -E2BIG)
> >   return kstrtoint(...);
> >
> > return 0;
> This is very nice way to do it. I'll update.
> ...
>
> --
> Muhammad Usama Anjum