[PATCH 3/3] HID: i2c-hid-of: Fall back to ACPI _DSM when hid-descr-addr is missing

["谢致邦 (XIE Zhibang)" <Yeking@Red54.com>]

Before commit b33752c30023 ("HID: i2c-hid: Reorganize so ACPI and OF are
separate modules"), the unified i2c-hid driver handled both PNP0C50 ACPI
devices and hid-over-i2c OF devices. After the split, devices with _HID
"PRP0001" and _DSD compatible "hid-over-i2c" are only probed by
i2c_hid_of, which requires "hid-descr-addr" in the _DSD. Some devices,
for example the Lenovo KaiTian N60d and Inspur CP300L3, provide the HID
descriptor address only through the _DSM method. Call the common
i2c_hid_core_acpi_get_descriptor() helper as a fallback, and set safe
post-power-on and post-reset-deassert delays.

Fixes: b33752c30023 ("HID: i2c-hid: Reorganize so ACPI and OF are separate modules")
Signed-off-by: 谢致邦 (XIE Zhibang) <Yeking@Red54.com>
---
 drivers/hid/i2c-hid/i2c-hid-of.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/hid/i2c-hid/i2c-hid-of.c b/drivers/hid/i2c-hid/i2c-hid-of.c
index 57379b77e977..e925e2d2cfe0 100644
--- a/drivers/hid/i2c-hid/i2c-hid-of.c
+++ b/drivers/hid/i2c-hid/i2c-hid-of.c
@@ -92,6 +92,36 @@ static int i2c_hid_of_probe(struct i2c_client *client)
 	ihid_of->ops.power_down = i2c_hid_of_power_down;
 
 	ret = device_property_read_u32(dev, "hid-descr-addr", &val);
+	if (ret) {
+		/*
+		 * Some devices, for example the Lenovo KaiTian N60d and Inspur
+		 * CP300L3, declare their I2C HID touchpad with _HID "PRP0001"
+		 * and _DSD compatible "hid-over-i2c" but lack the
+		 * "hid-descr-addr" property. Fall back to _DSM to obtain the
+		 * HID descriptor address.
+		 */
+		int dsm_ret = i2c_hid_core_acpi_get_descriptor(dev);
+
+		if (dsm_ret >= 0) {
+			dev_warn(dev,
+				 "hid-descr-addr NOT found, using _DSM fallback. Contact vendor for firmware update!\n");
+			val = dsm_ret;
+
+			/*
+			 * Firmware providing the descriptor address only
+			 * through _DSM may also lack "post-power-on-delay-ms"
+			 * or "post-reset-deassert-delay-ms", leaving the
+			 * driver without enough delay before the first HID
+			 * descriptor read. Set safe defaults to avoid reading
+			 * the descriptor before the device has finished its
+			 * internal power-on reset.
+			 */
+			ihid_of->post_power_delay_ms = 250;
+			ihid_of->post_reset_delay_ms = 250;
+
+			ret = 0;
+		}
+	}
 	if (ret) {
 		dev_err(dev, "HID register address not provided\n");
 		return -ENODEV;
-- 
2.54.0