Disable default auto-centering of the Logitech G940, which otherwise
makes the stick difficult to use. Also when autocenter is requested, obey
the magnitude.
The auto-centering effect will only unlock (or become the requested
level) when an application starts using the joystick and the hand sensor
on the stick is covered. That appears to be a hardware limitation.
To make the above and future work on spring/damper support simpler and
more type-safe, add a struct of the HID report. Many thanks to fred41 from
forums.x-plane.org for useful information towards that.
It seems byte 0 does not need to be a "command byte" of 0x51; it can be
anything and is the least-significant byte of the constant force.
Signed-off-by: Chris Boyle <chris@xxxxxxxxxx>
---
drivers/hid/hid-lg3ff.c | 148 +++++++++++++++++++++-------------------
1 file changed, 78 insertions(+), 70 deletions(-)
diff --git a/drivers/hid/hid-lg3ff.c b/drivers/hid/hid-lg3ff.c
index 8c2da183d3bc..6fcd449d5b46 100644
--- a/drivers/hid/hid-lg3ff.c
+++ b/drivers/hid/hid-lg3ff.c
@@ -2,6 +2,7 @@
* Force feedback support for Logitech Flight System G940
*
* Copyright (c) 2009 Gary Stein <LordCnidarian@xxxxxxxxx>
+ * Copyright (c) 2019 Chris Boyle
*/
/*
@@ -26,51 +27,68 @@
#include "hid-lg.h"
-/*
- * G940 Theory of Operation (from experimentation)
- *
- * There are 63 fields (only 3 of them currently used)
- * 0 - seems to be command field
- * 1 - 30 deal with the x axis
- * 31 -60 deal with the y axis
- *
- * Field 1 is x axis constant force
- * Field 31 is y axis constant force
- *
- * other interesting fields 1,2,3,4 on x axis
- * (same for 31,32,33,34 on y axis)
- *
- * 0 0 127 127 makes the joystick autocenter hard
- *
- * 127 0 127 127 makes the joystick loose on the right,
- * but stops all movemnt left
- *
- * -127 0 -127 -127 makes the joystick loose on the left,
- * but stops all movement right
- *
- * 0 0 -127 -127 makes the joystick rattle very hard
- *
- * I'm sure these are effects that I don't know enough about them
- */
+/* Ensure we remember to swap bytes (there's no sle16) */
+typedef __s16 __bitwise lg3_s16;
-struct lg3ff_device {
- struct hid_report *report;
-};
+static inline lg3_s16 lg3ff_cpu_to_sle16(s16 val)
+{
+ return (__force lg3_s16)cpu_to_le16(val);
+}
+
+struct hid_lg3ff_axis {
+ lg3_s16 constant_force; /* can cancel autocenter on relevant side */
+ u8 _padding0; /* extra byte of strength? no apparent effect */
+ /* how far towards center does the effect keep pushing:
+ * 0 = no autocenter, up to:
+ * 127 = push immediately on any deflection
+ * <0 = repel center
+ */
+ s8 autocenter_strength;
+ /* how hard does autocenter push */
+ s8 autocenter_force;
+ /* damping with force of autocenter_force (see also damper_*) */
+ s8 autocenter_damping;
+ lg3_s16 spring_deadzone_neg; /* for offset center, set these equal */
+ lg3_s16 spring_deadzone_pos;
+ s8 spring_coeff_neg; /* <0 repels center */
+ s8 spring_coeff_pos;
+ lg3_s16 spring_saturation;
+ u8 _padding1[8]; /* [4-8]: a different way of autocentering? */
+ s8 damper_coeff_neg;
+ s8 damper_coeff_pos;
+ lg3_s16 damper_saturation;
+ u8 _padding2[4]; /* seems to do the same as damper*? */
+} __packed;
+
+struct hid_lg3ff_report {
+ struct hid_lg3ff_axis x;
+ struct hid_lg3ff_axis y;
+ u8 _padding[3];
+} __packed;
+
+#define FF_REPORT_ID 2
+
+static void hig_lg3ff_send(struct input_dev *idev,
+ struct hid_lg3ff_report *raw_rep)
+{
+ struct hid_device *hid = input_get_drvdata(idev);
+ struct hid_report *hid_rep = hid->report_enum[HID_OUTPUT_REPORT]
+ .report_id_hash[FF_REPORT_ID];
+ int i;
+
+ /* We can be called while atomic (via hid_lg3ff_play) and must queue;
+ * there's nowhere to enqueue a raw report, so populate a hid_report.
+ */
+ for (i = 0; i < sizeof(*raw_rep); i++)
+ hid_rep->field[0]->value[i] = ((u8 *)raw_rep)[i];
+ hid_hw_request(hid, hid_rep, HID_REQ_SET_REPORT);
+}
static int hid_lg3ff_play(struct input_dev *dev, void *data,
struct ff_effect *effect)
{
- struct hid_device *hid = input_get_drvdata(dev);
- struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
- struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
- int x, y;
-
-/*
- * Available values in the field should always be 63, but we only use up to
- * 35. Instead, clear the entire area, however big it is.
- */
- memset(report->field[0]->value, 0,
- sizeof(__s32) * report->field[0]->report_count);
+ struct hid_lg3ff_report report = {0};
+ s16 x, y;
switch (effect->type) {
case FF_CONSTANT:
@@ -78,46 +96,32 @@ static int hid_lg3ff_play(struct input_dev *dev, void *data,
* Already clamped in ff_memless
* 0 is center (different then other logitech)
*/
- x = effect->u.ramp.start_level;
- y = effect->u.ramp.end_level;
-
- /* send command byte */
- report->field[0]->value[0] = 0x51;
+ x = -effect->u.ramp.start_level << 8;
+ y = -effect->u.ramp.end_level << 8;
/*
* Sign backwards from other Force3d pro
* which get recast here in two's complement 8 bits
*/
- report->field[0]->value[1] = (unsigned char)(-x);
- report->field[0]->value[31] = (unsigned char)(-y);
-
- hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+ report.x.constant_force = lg3ff_cpu_to_sle16(x);
+ report.y.constant_force = lg3ff_cpu_to_sle16(y);
+ hig_lg3ff_send(dev, &report);
break;
}
return 0;
}
static void hid_lg3ff_set_autocenter(struct input_dev *dev, u16 magnitude)
{
- struct hid_device *hid = input_get_drvdata(dev);
- struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
- struct hid_report *report = list_entry(report_list->next, struct hid_report, list);
+ struct hid_lg3ff_report report = {0};
-/*
- * Auto Centering probed from device
- * NOTE: deadman's switch on G940 must be covered
- * for effects to work
- */
- report->field[0]->value[0] = 0x51;
- report->field[0]->value[1] = 0x00;
- report->field[0]->value[2] = 0x00;
- report->field[0]->value[3] = 0x7F;
- report->field[0]->value[4] = 0x7F;
- report->field[0]->value[31] = 0x00;
- report->field[0]->value[32] = 0x00;
- report->field[0]->value[33] = 0x7F;
- report->field[0]->value[34] = 0x7F;
-
- hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+ /* negative means repel from center, so scale to 0-127 */
+ s8 mag_scaled = magnitude >> 9;
+
+ report.x.autocenter_strength = 127;
+ report.x.autocenter_force = mag_scaled;
+ report.y.autocenter_strength = 127;
+ report.y.autocenter_force = mag_scaled;
+ hig_lg3ff_send(dev, &report);
}
@@ -136,7 +140,9 @@ int lg3ff_init(struct hid_device *hid)
int i;
/* Check that the report looks ok */
- if (!hid_validate_values(hid, HID_OUTPUT_REPORT, 0, 0, 35))
+ BUILD_BUG_ON(sizeof(struct hid_lg3ff_report) != 63); /* excl. id */
+ if (!hid_validate_values(hid, HID_OUTPUT_REPORT, FF_REPORT_ID, 0,
+ sizeof(struct hid_lg3ff_report)))
return -ENODEV;
/* Assume single fixed device G940 */
@@ -147,8 +153,10 @@ int lg3ff_init(struct hid_device *hid)
if (error)
return error;
- if (test_bit(FF_AUTOCENTER, dev->ffbit))
+ if (test_bit(FF_AUTOCENTER, dev->ffbit)) {
dev->ff->set_autocenter = hid_lg3ff_set_autocenter;
+ hid_lg3ff_set_autocenter(dev, 0);
+ }
hid_info(hid, "Force feedback for Logitech Flight System G940 by Gary Stein <LordCnidarian@xxxxxxxxx>\n");
return 0;
--
2.17.1
--
Chris Boyle
https://chris.boyle.name/
