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From:   Dmitry Torokhov <dtor@chromium.org>
Date:   Fri, 8 Mar 2019 14:01:07 -0800
Message-ID: <CAE_wzQ-Ds5a9iPuLTpV5mBHBtoUUh_-fRw66s0Su7eOifygqKQ@mail.gmail.com>
Subject: Re: [PATCH] platform/chrome: Add Wilco EC keyboard backlight LEDs support
To:     Nick Crews <ncrews@chromium.org>
Cc:     enric.balletbo@collabora.com, Benson Leung <bleung@chromium.org>,
        linux-leds@vger.kernel.org, jacek.anaszewski@gmail.com,
        Pavel Machek <pavel@ucw.cz>,
        lkml <linux-kernel@vger.kernel.org>, dlaurie@chromium.org,
        Daniel Erat <derat@google.com>,
        Guenter Roeck <groeck@google.com>
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On Fri, Mar 8, 2019 at 12:41 PM Nick Crews <ncrews@chromium.org> wrote:
>
> This patch is meant to be applied on top of the for-next
> branch of the platform/chrome repository, as it uses some of
> the code staged there.
>
> The EC is in charge of controlling the keyboard backlight on
> the Wilco platform. We expose a standard LED class device at
> /sys/class/leds/wilco::kbd_backlight. This driver is modeled
> after the standard Chrome OS keyboard backlight driver at
> drivers/platform/chrome/cros_kbd_led_backlight.c
>
> Some Wilco devices do not support a keyboard backlight. This
> is checked in probe(), and in this case the sysfs entry will
> not appear, and everything will behave normally.

It would be even better if we did not register platform device if EC
does not support backlight.

> +       data->led.brightness_set = keyboard_led_set_brightness;
> +       data->led.brightness_get = keyboard_led_get_brightness;

wilco_ec_mailbox() may sleep, so you need to assign it to
led.brightness_set_blocking.

Thanks,
Dmitry