I am running Fedora 28 and Android-x86 on a Dell Latitude 5175 tablet. The
power button functionality is driven by the intel-hid driver. I am using
kernel version 4.16.
Currently, the intel-hid driver does not supply a KEY_POWER up event in cases
where the platform doesn't expose the 5-button array. Without this patch, the
power button can't reliably respond when the platform is running Android.
When running Fedora, I can use the power button to suspend and resume the
tablet. I can initiate this suspend by short-pressing the power button for a
second, and can resume it using another short-press.
When running Android-x86, I can only short-press the power button once. After
the press, the button seems to no longer respond. This is problematic when
using a short-press to initiate a suspend, since a subsequent short press will
not wake the tablet.
I used getevent to display the KeyEvents[1] detected by Android, and a
combination of 'cat /proc/kmsg' and debug statements in the intel-hid driver
to display the events generated by the driver. I found the block in the intel-
hid driver that generates power button events for my device. On line 253 of
intel-hid.c:
if (!priv->array) {
if (event == 0xce) {
input_report_key(priv->input_dev, KEY_POWER, 1);
input_sync(priv->input_dev);
return;
}
if (event == 0xcf)
return;
}
When I short-press the power button, intel-hid produces a KEY_POWER down
event, but doesn't produce a KEY_POWER up event when I release the power
button. Suppose intel-hid has been mapped to the input device /dev/input/
event19. Then, on Android-x86, the command "getevent -lt" produces the
following output:
/dev/input/event19: EV_KEY KEY_POWER DOWN
/dev/input/event19: EV_SYN SYN_REPORT 00000000
Subsequent presses produced no output for that input device.
When I added a call to input_report_key(...) and input_sync(...) on the
KEY_POWER up event in the intel-hid driver, I could repeatedly short-press the
power button and have Android respond appropriately, including resuming the
device from suspend. My hunch as to why this is the case is that Android needs
a paired KEY_POWER DOWN and UP event before it will handle the press.
>From 13f7f1cd9dfb71275f41dc598b17a92503fb991c Mon Sep 17 00:00:00 2001
From: Tristian Celestin <tristian.celestin@xxxxxxxxxxx>
Date: Tue, 10 Apr 2018 00:52:53 -0400
Subject: [PATCH] Make power-button key report the button-up event when the
5-button array does not exist.
---
drivers/platform/x86/intel-hid.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/drivers/platform/x86/intel-hid.c b/drivers/platform/x86/intel-hid.c
index 5e3df19..170ad950 100644
--- a/drivers/platform/x86/intel-hid.c
+++ b/drivers/platform/x86/intel-hid.c
@@ -260,6 +260,8 @@ static void notify_handler(acpi_handle handle, u32 event, void *context)
}
if (event == 0xcf)
+ input_report_key(priv->input_dev, KEY_POWER, 0);
+ input_sync(priv->input_dev);
return;
}
--
1.8.3.1
