Re: [PATCH] Input: add bu21029 touch driver

Hello Dmitry,

quoted

+++ b/drivers/input/touchscreen/bu21029_ts.c

@@ -0,0 +1,456 @@

Please add SPDX tag for the driver.

We will do.

Please use GPIOD API (and include linux/gpio/consumer.h instead of
of_gpio.h).

We will do the change.

quoted

+/* HW_ID1 Register (PAGE=0, ADDR=0x0E, Reset value=0x02, Read only)

Multi-line comments start with empty comment line:

/*
 * Multi
 * line.
 */

Will be fixed.

quoted

+	/* calculate Rz (pressure resistance value) by equation:
+	 * Rz = Rx * (x/Q) * ((z2/z1) - 1), where
+	 * Rx is x-plate resistance,
+	 * Q  is the touch screen resolution (8bit = 256, 12bit = 4096)
+	 * x, z1, z2 are the measured positions.
+	 */
+	rz  = z2 - z1;
+	rz *= x;
+	rz *= bu21029->x_plate_ohms;
+	rz /= z1;
+	rz  = DIV_ROUND_CLOSEST(rz, SCALE_12BIT);
+	if (rz <= bu21029->max_pressure) {
+		input_report_abs(bu21029->in_dev, ABS_X, x);
+		input_report_abs(bu21029->in_dev, ABS_Y, y);
+		input_report_abs(bu21029->in_dev, ABS_PRESSURE, rz);

What is the values of pressure reported when finger is touching the
surface? IOW is 'rz' pressure or resistance?

Rz is pressure measured in Ohms. That is, it is a resistance which
correlates with finger pressure.

I fear that I do not understand your question. Does ABS_PRESSURE have
to be reported in a specific unit, e.g. milli Newton? We thought that
it is a device specific scale and that it will be converted into a
calibrated value (just like the coordinates) in user space.

quoted

+	if (of_property_read_u32(np, "touchscreen-max-pressure", &val32))
+		bu21029->max_pressure = MAX_12BIT;
+	else
+		bu21029->max_pressure = val32;

Please use infrastructure form include/linux/input/touchscreen.h
so that you handle different sizes and orientations.

Thank you for this recommendation. We will check it out and send a new
proposal.

quoted

+	in_dev->name       = DRIVER_NAME;
+	in_dev->id.bustype = BUS_I2C;
+	in_dev->dev.parent = &client->dev;

Not needed with devm_input_allocate_device().

We will have a look at the other drivers.

quoted

+static int bu21029_remove(struct i2c_client *client)
+{
+	struct bu21029_ts_data *bu21029 = i2c_get_clientdata(client);
+
+	del_timer_sync(&bu21029->timer);

If interrupt comes here kernel will be unhappy. You need to either work
canceling timer into devm unwid stream (devm_add_action_or_reset()) or
somehow make sure that you shut off interrupts before canceling the
timer.

We will work on a solution. Thank you for spotting this.

quoted

+
+	return 0;
+}

quoted

+static struct i2c_driver bu21029_driver = {
+	.driver = {
+		.name  = DRIVER_NAME,
+		.owner = THIS_MODULE,

Not needed.

OK, we will remove the .owner assignment.

Greetings,
Mark Jonas

Building Technologies, Panel Software Fire (BT-FIR/ENG1) 
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