[PATCH 2/2] HID: Make elan touch controllers power on after panel is enabled

Pin-Yen Lin
2025-07-31T10:13:55Z

Introduce a new HID quirk to indicate that this device has to be enabled
after the panel's backlight is enabled, and update the driver data for
the elan devices to enable this quirk. This cannot be a I2C HID quirk
because the kernel needs to acknowledge this before powering up the
device and read the VID/PID.

Signed-off-by: Pin-Yen Lin <treapking@google.com>

---

drivers/hid/i2c-hid/i2c-hid-core.c | 2 ++
drivers/hid/i2c-hid/i2c-hid-of-elan.c | 11 ++++++++++-
include/linux/hid.h | 2 ++
3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
index d3912e3f2f13a..8dc4d5d56d399 100644
--- a/drivers/hid/i2c-hid/i2c-hid-core.c
+++ b/drivers/hid/i2c-hid/i2c-hid-core.c
@@ -1183,6 +1183,8 @@ static int i2c_hid_core_register_panel_follower(struct i2c_hid *ihid)
int ret;

ihid->panel_follower.funcs = &i2c_hid_core_panel_follower_funcs;
+ if (ihid->hid->initial_quirks | HID_QUIRK_POWER_ON_AFTER_BACKLIGHT)
+ ihid->panel_follower.after_panel_enabled = true;

/*
* If we're not in control of our own power up/power down then we can't
diff --git a/drivers/hid/i2c-hid/i2c-hid-of-elan.c b/drivers/hid/i2c-hid/i2c-hid-of-elan.c
index 3fcff6daa0d3a..0215f217f6d86 100644
--- a/drivers/hid/i2c-hid/i2c-hid-of-elan.c
+++ b/drivers/hid/i2c-hid/i2c-hid-of-elan.c
@@ -8,6 +8,7 @@
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/gpio/consumer.h>
+#include <linux/hid.h>
#include <linux/i2c.h>
#include <linux/kernel.h>
#include <linux/module.h>
@@ -23,6 +24,7 @@ struct elan_i2c_hid_chip_data {
unsigned int post_power_delay_ms;
u16 hid_descriptor_address;
const char *main_supply_name;
+ bool power_after_backlight;
};

struct i2c_hid_of_elan {
@@ -97,6 +99,7 @@ static int i2c_hid_of_elan_probe(struct i2c_client *client)
{
struct i2c_hid_of_elan *ihid_elan;
int ret;
+ u32 quirks = 0;

ihid_elan = devm_kzalloc(&client->dev, sizeof(*ihid_elan), GFP_KERNEL);
if (!ihid_elan)
@@ -131,8 +134,12 @@ static int i2c_hid_of_elan_probe(struct i2c_client *client)
}
}

+ if (ihid_elan->chip_data->power_after_backlight)
+ quirks = HID_QUIRK_POWER_ON_AFTER_BACKLIGHT;
+
ret = i2c_hid_core_probe(client, &ihid_elan->ops,
- ihid_elan->chip_data->hid_descriptor_address, 0);
+ ihid_elan->chip_data->hid_descriptor_address,
+ quirks);
if (ret)
goto err_deassert_reset;

@@ -150,6 +157,7 @@ static const struct elan_i2c_hid_chip_data elan_ekth6915_chip_data = {
.post_gpio_reset_on_delay_ms = 300,
.hid_descriptor_address = 0x0001,
.main_supply_name = "vcc33",
+ .power_after_backlight = true,
};

static const struct elan_i2c_hid_chip_data elan_ekth6a12nay_chip_data = {
@@ -157,6 +165,7 @@ static const struct elan_i2c_hid_chip_data elan_ekth6a12nay_chip_data = {
.post_gpio_reset_on_delay_ms = 300,
.hid_descriptor_address = 0x0001,
.main_supply_name = "vcc33",
+ .power_after_backlight = true,
};

static const struct elan_i2c_hid_chip_data ilitek_ili9882t_chip_data = {
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 2cc4f1e4ea963..c32425b5d0119 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -364,6 +364,7 @@ struct hid_item {
* | @HID_QUIRK_HAVE_SPECIAL_DRIVER:
* | @HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE:
* | @HID_QUIRK_IGNORE_SPECIAL_DRIVER
+ * | @HID_QUIRK_POWER_ON_AFTER_BACKLIGHT
* | @HID_QUIRK_FULLSPEED_INTERVAL:
* | @HID_QUIRK_NO_INIT_REPORTS:
* | @HID_QUIRK_NO_IGNORE:
@@ -391,6 +392,7 @@ struct hid_item {
#define HID_QUIRK_INCREMENT_USAGE_ON_DUPLICATE BIT(20)
#define HID_QUIRK_NOINVERT BIT(21)
#define HID_QUIRK_IGNORE_SPECIAL_DRIVER BIT(22)
+#define HID_QUIRK_POWER_ON_AFTER_BACKLIGHT BIT(23)
#define HID_QUIRK_FULLSPEED_INTERVAL BIT(28)
#define HID_QUIRK_NO_INIT_REPORTS BIT(29)
#define HID_QUIRK_NO_IGNORE BIT(30)
--
2.50.1.552.g942d659e1b-goog