Re: [PATCH v3 7/8] platform/chrome: cros_ec_lightbar: instantiate only if the EC has a lightbar.

[Guenter Roeck <groeck@google.com>]

On Tue, Nov 27, 2018 at 4:19 AM Enric Balletbo i Serra
<enric.balletbo@collabora.com> wrote:
>
> Due to the way attribute groups visibility work, the function
> cros_ec_lightbar_attrs_are_visible is called multiple times, once per
> attribute, and each of these calls makes an EC transaction. For what is
> worth the EC log reports multiple errors on boot when the lightbar is
> not available. Instead, check if the EC has a lightbar in the probe
> function and only instantiate the device.
>
> Ideally we should have instantiate the driver only if the
> EC_FEATURE_LIGHTBAR is defined, but that's not possible because that flag
> is not in the very first Pixel Chromebook (Link), only on Samus. So, the
> driver is instantiated by his parent always.
>
> This patch changes a bit the actual behaviour. Before the patch if an EC
> doesn't have a lightbar an empty lightbar folder is created in
> /sys/class/chromeos/<ec device>, after the patch the empty folder is not
> created, so, the folder is only created if the lightbar exists.
>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

Nitpicks, otherwise

Reviewed-by: Guenter Roeck <groeck@chromium.org>

> ---
>
> Changes in v3: None
> Changes in v2:
> - Removed ec_with_lightbar variable.
>
>  drivers/platform/chrome/cros_ec_lightbar.c | 37 ++++++++--------------
>  1 file changed, 13 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/platform/chrome/cros_ec_lightbar.c b/drivers/platform/chrome/cros_ec_lightbar.c
> index 80eed6317570..6f6a4cbfc3fc 100644
> --- a/drivers/platform/chrome/cros_ec_lightbar.c
> +++ b/drivers/platform/chrome/cros_ec_lightbar.c
> @@ -43,7 +43,6 @@ static unsigned long lb_interval_jiffies = 50 * HZ / 1000;
>   * If this is true, we won't do anything during suspend/resume.
>   */
>  static bool userspace_control;
> -static struct cros_ec_dev *ec_with_lightbar;
>
>  static ssize_t interval_msec_show(struct device *dev,
>                                   struct device_attribute *attr, char *buf)
> @@ -381,9 +380,6 @@ static int lb_manual_suspend_ctrl(struct cros_ec_dev *ec, uint8_t enable)
>         struct cros_ec_command *msg;
>         int ret;
>
> -       if (ec != ec_with_lightbar)
> -               return 0;
> -
>         msg = alloc_lightbar_cmd_msg(ec);
>         if (!msg)
>                 return -ENOMEM;
> @@ -567,37 +563,26 @@ static struct attribute *__lb_cmds_attrs[] = {
>         NULL,
>  };
>
> -static bool ec_has_lightbar(struct cros_ec_dev *ec)
> +static bool cros_ec_has_lightbar(struct cros_ec_dev *ec_dev)
>  {
> -       return !!get_lightbar_version(ec, NULL, NULL);
> -}
> -
> -static umode_t cros_ec_lightbar_attrs_are_visible(struct kobject *kobj,
> -                                                 struct attribute *a, int n)
> -{
> -       struct device *dev = container_of(kobj, struct device, kobj);
> -       struct cros_ec_dev *ec = to_cros_ec_dev(dev);
> -       struct platform_device *pdev = to_platform_device(ec->dev);
> +       struct platform_device *pdev = to_platform_device(ec_dev->dev);
>         struct cros_ec_platform *pdata = pdev->dev.platform_data;
>         int is_cros_ec;
>
>         is_cros_ec = strcmp(pdata->ec_name, CROS_EC_DEV_NAME);
>
>         if (is_cros_ec != 0)
> -               return 0;
> +               return false;
>
FWIW, is_cros_ec is really unnecessary here, though I guess that might
be a different patch.

> -       /* Only instantiate this stuff if the EC has a lightbar */
> -       if (ec_has_lightbar(ec)) {
> -               ec_with_lightbar = ec;
> -               return a->mode;
> -       }
> -       return 0;
> +       if (!!get_lightbar_version(ec_dev, NULL, NULL))
> +               return true;
> +
> +       return false;

Why not just the following ?
            return !!get_lightbar_version(ec_dev, NULL, NULL);
or even
            return !strcmp(pdata->ec_name, CROS_EC_DEV_NAME) &&
                      !!get_lightbar_version(ec_dev, NULL, NULL);

>  }
>
>  struct attribute_group cros_ec_lightbar_attr_group = {
>         .name = "lightbar",
>         .attrs = __lb_cmds_attrs,
> -       .is_visible = cros_ec_lightbar_attrs_are_visible,
>  };
>
>  static int cros_ec_lightbar_probe(struct platform_device *pd)
> @@ -606,6 +591,10 @@ static int cros_ec_lightbar_probe(struct platform_device *pd)
>         struct device *dev = &pd->dev;
>         int ret;
>
> +       /* Only instantiate this stuff if the EC has a lightbar */
> +       if (!cros_ec_has_lightbar(ec_dev))
> +               return -ENODEV;
> +
>         /* Take control of the lightbar from the EC. */
>         lb_manual_suspend_ctrl(ec_dev, 1);
>
> @@ -635,7 +624,7 @@ static int __maybe_unused cros_ec_lightbar_resume(struct device *dev)
>  {
>         struct cros_ec_dev *ec_dev = dev_get_drvdata(dev);
>
> -       if (userspace_control || ec_dev != ec_with_lightbar)
> +       if (userspace_control)
>                 return 0;
>
>         return lb_send_empty_cmd(ec_dev, LIGHTBAR_CMD_RESUME);
> @@ -645,7 +634,7 @@ static int __maybe_unused cros_ec_lightbar_suspend(struct device *dev)
>  {
>         struct cros_ec_dev *ec_dev = dev_get_drvdata(dev);
>
> -       if (userspace_control || ec_dev != ec_with_lightbar)
> +       if (userspace_control)
>                 return 0;
>
>         return lb_send_empty_cmd(ec_dev, LIGHTBAR_CMD_SUSPEND);
> --
> 2.19.1
>