On Tue, Jul 3, 2018 at 10:47 PM, Nick Dyer <nick@xxxxxxxxxxxxx> wrote:
> With surface capacitance touchscreens the capacitance is measured
> through readings obtained from measurements taken at the four
> corners of the glass. These measurements are accessible in the I/Q
> modulation format from the the controller which becomes meaningful
> data when converted to an absolute value using the pythagorean
> theorem.
>
> Signed-off-by: Nick Dyer <nick@xxxxxxxxxxxxx>
> ---
> Changes in v2:
> - Values read from device must be treated as signed
>
Numbers validated against a user-space tool that also reads stray
values from the controller.
Tested-by: Aleksander Morgado <aleksander@xxxxxxxxxxxxx>
> drivers/input/touchscreen/usbtouchscreen.c | 58 ++++++++++++++++++++++
> 1 file changed, 58 insertions(+)
>
> diff --git a/drivers/input/touchscreen/usbtouchscreen.c b/drivers/input/touchscreen/usbtouchscreen.c
> index d61570d64ee7..af8fb1ab3a67 100644
> --- a/drivers/input/touchscreen/usbtouchscreen.c
> +++ b/drivers/input/touchscreen/usbtouchscreen.c
> @@ -55,6 +55,7 @@
> #include <linux/usb/input.h>
> #include <linux/hid.h>
> #include <linux/mutex.h>
> +#include <asm/unaligned.h>
>
> static bool swap_xy;
> module_param(swap_xy, bool, 0644);
> @@ -437,11 +438,18 @@ static int panjit_read_data(struct usbtouch_usb *dev, unsigned char *pkt)
> #ifdef CONFIG_TOUCHSCREEN_USB_3M
>
> #define MTOUCHUSB_ASYNC_REPORT 1
> +#define MTOUCHUSB_GET_BLOCK 2
> +#define MTOUCHUSB_STRAYS_BLOCK_CMD 3
> #define MTOUCHUSB_RESET 7
> #define MTOUCHUSB_REQ_CTRLLR_ID 10
>
> #define MTOUCHUSB_REQ_CTRLLR_ID_LEN 16
>
> +struct mtouch_strays {
> + u8 hdr[3];
> + __le32 data[8];
> +} __attribute__ ((packed));
> +
> static int mtouch_read_data(struct usbtouch_usb *dev, unsigned char *pkt)
> {
> if (hwcalib_xy) {
> @@ -459,8 +467,22 @@ static int mtouch_read_data(struct usbtouch_usb *dev, unsigned char *pkt)
> struct mtouch_priv {
> u8 fw_rev_major;
> u8 fw_rev_minor;
> + u64 strays[4];
> };
>
> +static ssize_t mtouch_strays_show(struct device *dev,
> + struct device_attribute *attr, char *output)
> +{
> + struct usb_interface *intf = to_usb_interface(dev);
> + struct usbtouch_usb *usbtouch = usb_get_intfdata(intf);
> + struct mtouch_priv *priv = usbtouch->priv;
> +
> + return scnprintf(output, PAGE_SIZE, "ul=%llu ur=%llu ll=%llu lr=%llu\n",
> + priv->strays[0], priv->strays[1],
> + priv->strays[2], priv->strays[3]);
> +}
> +static DEVICE_ATTR(strays, 0444, mtouch_strays_show, NULL);
> +
> static ssize_t mtouch_firmware_rev_show(struct device *dev,
> struct device_attribute *attr, char *output)
> {
> @@ -475,6 +497,7 @@ static DEVICE_ATTR(firmware_rev, 0444, mtouch_firmware_rev_show, NULL);
>
> static struct attribute *mtouch_attrs[] = {
> &dev_attr_firmware_rev.attr,
> + &dev_attr_strays.attr,
> NULL
> };
>
> @@ -482,6 +505,39 @@ static const struct attribute_group mtouch_attr_group = {
> .attrs = mtouch_attrs,
> };
>
> +static void mtouch_get_strays_report(struct usbtouch_usb *usbtouch)
> +{
> + struct usb_device *udev = interface_to_usbdev(usbtouch->interface);
> + struct mtouch_priv *priv = usbtouch->priv;
> + struct mtouch_strays *sbuf;
> + int ret;
> + int i;
> +
> + sbuf = kzalloc(sizeof(struct mtouch_strays), GFP_NOIO);
> + if (!sbuf)
> + return;
> +
> + ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
> + MTOUCHUSB_GET_BLOCK,
> + USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
> + MTOUCHUSB_STRAYS_BLOCK_CMD,
> + 0, sbuf, sizeof(struct mtouch_strays),
> + USB_CTRL_SET_TIMEOUT);
> + if (ret != sizeof(struct mtouch_strays))
> + goto out_free;
> +
> + for (i = 0; i < 4; i++) {
> + s64 a, b;
> +
> + a = (s32)get_unaligned_le32(&sbuf->data[i*2]);
> + b = (s32)get_unaligned_le32(&sbuf->data[i*2 + 1]);
> + priv->strays[i] = int_sqrt64(a * a + b * b);
> + }
> +
> +out_free:
> + kfree(sbuf);
> +}
> +
> static int mtouch_get_fw_revision(struct usbtouch_usb *usbtouch)
> {
> struct usb_device *udev = interface_to_usbdev(usbtouch->interface);
> @@ -568,6 +624,8 @@ static int mtouch_init(struct usbtouch_usb *usbtouch)
> return ret;
> }
>
> + mtouch_get_strays_report(usbtouch);
> +
> /* Default min/max xy are the raw values, override if using hw-calib */
> if (hwcalib_xy) {
> input_set_abs_params(usbtouch->input, ABS_X, 0, 0xffff, 0, 0);
> --
> 2.17.1
>
--
Aleksander
https://aleksander.es
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