[RFC PATCH 3/3] HID: spi-hid-of: add the Surface Pro X touch digitizer

[Tawheed Makhdoomi <_@tawheed.cc>]

The Surface Pro X digitizer speaks the pre-release HID over SPI protocol
revision. Both the input report header and body are read from 0x1000
with opcode 0x0b, and the device descriptor is requested from register 1
with opcode 0x02; the other registers come from the device descriptor.

Add match data for it, with the same timings as the G6 digitizer, under
the "microsoft,surface-pro-x-touch-digitizer" compatible and SPI device
ID.

Signed-off-by: Tawheed Makhdoomi <_@tawheed.cc>
---
 drivers/hid/spi-hid/spi-hid-of.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/hid/spi-hid/spi-hid-of.c b/drivers/hid/spi-hid/spi-hid-of.c
index 6de9affbe..429bf51ad 100644
--- a/drivers/hid/spi-hid/spi-hid-of.c
+++ b/drivers/hid/spi-hid/spi-hid-of.c
@@ -62,6 +62,24 @@ static const struct spi_hid_of_data microsoft_g6_data = {
 	.minimal_reset_delay_ms = 100,
 };
 
+/*
+ * The Surface Pro X digitizer implements the pre-release protocol revision.
+ * Input report header and body are both read from 0x1000, and the device
+ * descriptor is requested from register 1.
+ */
+static const struct spi_hid_of_data microsoft_surface_pro_x_data = {
+	.conf = {
+		.input_report_header_address = 0x1000,
+		.input_report_body_address = 0x1000,
+		.output_report_address = 0x1,
+		.read_opcode = 0x0b,
+		.write_opcode = 0x02,
+		.protocol = SPI_HID_PROTOCOL_V2,
+	},
+	.post_power_on_delay_ms = 10,
+	.minimal_reset_delay_ms = 100,
+};
+
 static int spi_hid_of_populate_config(struct spi_hid_of_config *conf,
 				      struct device *dev)
 {
@@ -181,12 +199,20 @@ static int spi_hid_of_probe(struct spi_device *spi)
 
 static const struct of_device_id spi_hid_of_match[] = {
 	{ .compatible = "microsoft,g6-touch-digitizer", .data = &microsoft_g6_data },
+	{
+		.compatible = "microsoft,surface-pro-x-touch-digitizer",
+		.data = &microsoft_surface_pro_x_data
+	},
 	{ }
 };
 MODULE_DEVICE_TABLE(of, spi_hid_of_match);
 
 static const struct spi_device_id spi_hid_of_id_table[] = {
 	{ .name = "g6-touch-digitizer", .driver_data = (kernel_ulong_t)&microsoft_g6_data },
+	{
+		.name = "surface-pro-x-touch-digitizer",
+		.driver_data = (kernel_ulong_t)&microsoft_surface_pro_x_data
+	},
 	{ }
 };
 MODULE_DEVICE_TABLE(spi, spi_hid_of_id_table);
-- 
2.43.0