Re: [PATCH] Add generic driver for Silead tochscreens

[Gregor Riepl <onitake@gmail.com>]

> In the datasheet there is no register map. Silead gave us a partial
> register map in order to implement the driver. In the map they
> provided there is no register for resolution or anything that would
> help with this issue. The information in [1] is incomplete and can not
> be considered reliable since the vendor does not say anything about
> it.

That is indeed true.
Relying on parameters read from the ACPI DSDT or the DeviceTree would
certainly be the "clean" way to go on new hardware, but it will not work on
existing hardware where the device parameters are fixed.

Do you think it would make sense to also allow passing the parameters as
module options, or via sysfs for cases where they can't be autodetected?

Also, while going over your code, I found something that might be incorrect.
When you evaluate the point data from the device, you are interpreting it with
this code:

#define SILEAD_POINT_DATA_LEN	0x04
#define SILEAD_POINT_X_OFF	0x02
#define SILEAD_POINT_ID_OFF	0x03
#define SILEAD_X_HSB_MASK	0xF0
#define SILEAD_TOUCH_ID_MASK	0x0F
for (i = 1; i <= touch_nr; i++) {
	offset = i * SILEAD_POINT_DATA_LEN;

	/* The last 4 bits are the touch id */
	id = buf[offset + SILEAD_POINT_ID_OFF] & SILEAD_TOUCH_ID_MASK;

	/* The 1st 4 bits are part of X */
	buf[offset + SILEAD_POINT_ID_OFF] =
		(buf[offset + SILEAD_POINT_ID_OFF] & SILEAD_X_HSB_MASK)
		>> 4;

	y = le16_to_cpup((__le16 *)(buf + offset));
	x = le16_to_cpup((__le16 *)(buf + offset + SILEAD_POINT_X_OFF));
}

The Basewin driver and all the ones derived from it interpreted it like this:

ts->dd = {
	.x_index = 6,
	.y_index = 4,
	.z_index = 5,
	.id_index = 7,
}
for(i= 0;i < (touches > MAX_FINGERS ? MAX_FINGERS : touches);i ++) {
	x = join_bytes( ( ts->touch_data[ts->dd->x_index + 4 * i + 1] & 0xf),
	ts->touch_data[ts->dd->x_index + 4 * i]);
	y = join_bytes(ts->touch_data[ts->dd->y_index + 4 * i + 1],
	ts->touch_data[ts->dd->y_index + 4 * i ]);
	id = ts->touch_data[ts->dd->id_index + 4 * i] >> 4;
}


Or, in other words, your code uses the second-to-last nibble of each record as
the touch id, while the Basewin code uses the last nibble (in little-endian
order).
Please correct me if I am wrong.