Hi Hans,

On Fri, Feb 17, 2023 at 04:07:49PM +0100, Hans de Goede wrote:

Add a new driver for the Novatek i2c touchscreen controller as found
on the Acer Iconia One 7 B1-750 tablet. Unfortunately the touchscreen
controller model-number is unknown. Even with the tablet opened up it
is impossible to read the model-number.

Android calls this a "NVT-ts" touchscreen, but that may apply to other
Novatek controller models too.

This appears to be the same controller as the one supported by
https://github.com/advx9600/android/blob/master/touchscreen/NVTtouch_Android4.0/NVTtouch.c
but unfortunately that does not give us a model-number either.

Signed-off-by: Hans de Goede <redacted>

This is a great driver; I have only a few comments below.

Nit: there is no trailing comma here, yet one trails 'buf' below.

+		},
+		{
+			.addr = client->addr,
+			.flags = I2C_M_RD,
+			.len = count,
+			.buf = data,
+		}
+	};
+	int ret;
+
+	ret = i2c_transfer(client->adapter, msg, 2);
+	if (ret != 2) {
+		dev_err(&client->dev, "Error reading from 0x%02x: %d\n", reg, ret);
+		return (ret < 0) ? ret : -EIO;
+	}

This is idiomatic, but I feel it is clearer to write ARRAY_SIZE(msg) instead
of 2 throughout; this way the length is hard-coded only once.

+
+	return 0;
+}
+
+static irqreturn_t nvt_ts_irq(int irq, void *dev_id)
+{
+	struct nvt_ts_data *data = dev_id;
+	struct device *dev = &data->client->dev;
+	int i, ret, slot, x, y;

In input, return values for functions that only return zero on success tend to
be named 'error'.

+	bool active;
+	u8 *touch;
+
+	ret = nvt_ts_read_data(data->client, NVT_TS_TOUCH_START, data->buf,
+			       data->max_touches * NVT_TS_TOUCH_SIZE);
+	if (ret)
+		return IRQ_HANDLED;
+
+	for (i = 0; i < data->max_touches; i++) {
+		touch = &data->buf[i * NVT_TS_TOUCH_SIZE];
+
+		/* 0xff means no touch */
+		if (touch[0] == 0xff)
+			continue;
+
+		slot = touch[0] >> 3;
+		if (slot < 1 || slot > data->max_touches) {
+			dev_warn(dev, "slot %d out of range, ignoring\n", slot);
+			continue;
+		}
+
+		switch (touch[0] & 7) {

With all other fields and values defined so nicely, it seems most clear to
also define the bit field name in this case.

+		case NVT_TS_TOUCH_NEW:
+		case NVT_TS_TOUCH_UPDATE:
+			active = true;
+			break;
+		case NVT_TS_TOUCH_RELEASE:
+			active = false;
+			break;
+		default:
+			dev_warn(dev, "slot %d unknown state %d\n", slot, touch[0] & 7);
+			continue;
+		}
+
+		slot--;
+		x = (touch[1] << 4) | (touch[3] >> 4);
+		y = (touch[2] << 4) | (touch[3] & 0x0f);
+
+		input_mt_slot(data->input, slot);
+		input_mt_report_slot_state(data->input, MT_TOOL_FINGER, active);
+		touchscreen_report_pos(data->input, &data->prop, x, y, true);
+	}
+
+	input_mt_sync_frame(data->input);
+	input_sync(data->input);
+
+	return IRQ_HANDLED;
+}
+
+static int nvt_ts_start(struct input_dev *dev)
+{
+	struct nvt_ts_data *data = input_get_drvdata(dev);
+
+	enable_irq(data->client->irq);
+	gpiod_set_value_cansleep(data->reset_gpio, 0);
+
+	return 0;
+}
+
+static void nvt_ts_stop(struct input_dev *dev)
+{
+	struct nvt_ts_data *data = input_get_drvdata(dev);
+
+	disable_irq(data->client->irq);
+	gpiod_set_value_cansleep(data->reset_gpio, 1);
+}
+
+static int nvt_ts_suspend(struct device *dev)
+{
+	struct nvt_ts_data *data = i2c_get_clientdata(to_i2c_client(dev));
+
+	mutex_lock(&data->input->mutex);
+	if (input_device_enabled(data->input))
+		nvt_ts_stop(data->input);
+	mutex_unlock(&data->input->mutex);
+
+	return 0;
+}
+
+static int nvt_ts_resume(struct device *dev)
+{
+	struct nvt_ts_data *data = i2c_get_clientdata(to_i2c_client(dev));
+
+	mutex_lock(&data->input->mutex);
+	if (input_device_enabled(data->input))
+		nvt_ts_start(data->input);
+	mutex_unlock(&data->input->mutex);
+
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(nvt_ts_pm_ops, nvt_ts_suspend, nvt_ts_resume);
+
+static int nvt_ts_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	int ret, width, height, irq_type;
+	struct nvt_ts_data *data;
+	struct input_dev *input;
+
+	if (!client->irq) {
+		dev_err(dev, "Error no irq specified\n");
+		return -EINVAL;
+	}
+
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	data->client = client;
+	i2c_set_clientdata(client, data);
+
+	data->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
+	if (IS_ERR(data->reset_gpio))
+		return dev_err_probe(dev, PTR_ERR(data->reset_gpio), "requesting reset GPIO\n");
+
+	/* Wait for controller to come out of reset before params read */
+	msleep(100);
+	ret = nvt_ts_read_data(data->client, NVT_TS_PARAMETERS_START, data->buf,
+			       NVT_TS_PARAMS_SIZE);
+	gpiod_set_value_cansleep(data->reset_gpio, 1); /* Put back in reset */
+	if (ret)
+		return ret;
+
+	width  = get_unaligned_be16(&data->buf[NVT_TS_PARAMS_WIDTH]);
+	height = get_unaligned_be16(&data->buf[NVT_TS_PARAMS_HEIGHT]);
+	data->max_touches = data->buf[NVT_TS_PARAMS_MAX_TOUCH];
+	irq_type = data->buf[NVT_TS_PARAMS_IRQ_TYPE];
+
+	if (width > NVT_TS_MAX_SIZE || height >= NVT_TS_MAX_SIZE ||
+	    data->max_touches > NVT_TS_MAX_TOUCHES ||
+	    irq_type >= ARRAY_SIZE(nvt_ts_irq_type) ||
+	    data->buf[NVT_TS_PARAMS_WAKE_TYPE] != NVT_TS_SUPPORTED_WAKE_TYPE ||
+	    data->buf[NVT_TS_PARAMS_CHIP_ID] != NVT_TS_SUPPORTED_CHIP_ID) {
+		dev_err(dev, "Unsupported touchscreen parameters: %*ph\n",
+			NVT_TS_PARAMS_SIZE, data->buf);
+		return -EIO;

Nit: because there was no I/O error here necessarily, but rather invalid or
unacceptable values, I think -EINVAL is better here.

+	}
+
+	dev_info(dev, "Detected %dx%d touchscreen with %d max touches\n",
+		 width, height, data->max_touches);

This is also idiomatic, but this seems better as dev_dbg.

+
+	if (data->buf[NVT_TS_PARAMS_MAX_BUTTONS])
+		dev_warn(dev, "Touchscreen buttons are not supported\n");
+
+	input = devm_input_allocate_device(dev);
+	if (!input)
+		return -ENOMEM;
+
+	input->name = client->name;
+	input->id.bustype = BUS_I2C;
+	input->open = nvt_ts_start;
+	input->close = nvt_ts_stop;
+	input->dev.parent = dev;

devm_input_allocate_device() already sets the parent for us.

+
+	input_set_abs_params(input, ABS_MT_POSITION_X, 0, width - 1, 0, 0);
+	input_set_abs_params(input, ABS_MT_POSITION_Y, 0, height - 1, 0, 0);
+	touchscreen_parse_properties(input, true, &data->prop);
+
+	ret = input_mt_init_slots(input, data->max_touches,
+				  INPUT_MT_DIRECT | INPUT_MT_DROP_UNUSED);
+	if (ret)
+		return ret;
+
+	data->input = input;
+	input_set_drvdata(input, data);
+
+	ret = devm_request_threaded_irq(dev, client->irq, NULL, nvt_ts_irq,
+					IRQF_ONESHOT | IRQF_NO_AUTOEN | nvt_ts_irq_type[irq_type],
+					client->name, data);

Interesting, it seems interrupt polarity is configurable? For my own
understanding, what if there is an inverter on the board? Is the
expectation that the customer reprograms the controller's firmware?

+	if (ret)
+		return dev_err_probe(dev, ret, "requesting irq\n");

dev_err_probe() tends not to be accepted in input, the argument being
that the callers who can return EPROBE_DEFER be responsible for setting
the reason as opposed to every driver calling a separate function that
does so.

+
+	return input_register_device(input);
+}
+
+static const struct i2c_device_id nvt_ts_i2c_id[] = {
+	{ "NVT-ts" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, nvt_ts_i2c_id);
+
+static struct i2c_driver nvt_ts_driver = {
+	.driver = {
+		.name	= "novatek-nvt-ts",
+		.pm	= &nvt_ts_pm_ops,

I believe we need pm_sleep_ptr() here now.

+	},
+	.probe_new = nvt_ts_probe,
+	.id_table = nvt_ts_i2c_id,
+};
+
+module_i2c_driver(nvt_ts_driver);
+
+MODULE_DESCRIPTION("Novatek NVT-ts touchscreen driver");
+MODULE_AUTHOR("Hans de Goede [off-list ref]");
+MODULE_LICENSE("GPL");
-- 
2.39.1

Kind regards,
Jeff LaBundy