[v7,16/17] HID: pidff: Rescale period value to match device units

Commit Message

Tomasz Pakuła Jan. 25, 2025, 10:25 p.m. UTC

PID devices can use plethora of units for PERIODIC type effect period
while Linux Force Feedback API only supports miliseconds.

Read the exponent of the period field and scale period value accordingly.

Co-developed-by: Makarenko Oleg <[e-mail]>
Signed-off-by: Makarenko Oleg <[e-mail]>
Signed-off-by: Tomasz Pakuła <[e-mail]>
---
 drivers/hid/usbhid/hid-pidff.c | 37 ++++++++++++++++++++++++++++------
 1 file changed, 31 insertions(+), 6 deletions(-)

Patch

diff --git a/drivers/hid/usbhid/hid-pidff.c b/drivers/hid/usbhid/hid-pidff.c
index 575f24610269..c8a60034d477 100644
--- a/drivers/hid/usbhid/hid-pidff.c
+++ b/drivers/hid/usbhid/hid-pidff.c
@@ -22,6 +22,9 @@ 
 #define	PID_EFFECTS_MAX		64
 #define	PID_INFINITE		0xffff
 
+/* Linux Force Feedback API only supports miliseconds as period unit */
+#define FF_PERIOD_EXPONENT	-3
+
 /* Report usage table used to put reports into an array */
 
 #define PID_SET_EFFECT		0
@@ -231,6 +234,24 @@  static int pidff_rescale_signed(int i, struct hid_field *field)
 	    field->logical_minimum / -0x8000;
 }
 
+/*
+ * Scale period value to device's units from Linux default (ms)
+ */
+static s32 pidff_rescale_period(u16 period, struct hid_field *field)
+{
+	s32 scaled_period = period;
+	int exponent = field->unit_exponent;
+	pr_debug("period exponent: %d\n", exponent);
+
+	for (;exponent < FF_PERIOD_EXPONENT; exponent++)
+		scaled_period *= 10;
+	for (;exponent > FF_PERIOD_EXPONENT; exponent--)
+		scaled_period /= 10;
+
+	pr_debug("period calculated from %d to %d\n", period, scaled_period);
+	return scaled_period;
+}
+
 static void pidff_set(struct pidff_usage *usage, u16 value)
 {
 	usage->value[0] = pidff_rescale(value, 0xffff, usage->field);
@@ -252,6 +273,14 @@  static void pidff_set_signed(struct pidff_usage *usage, s16 value)
 	pr_debug("calculated from %d to %d\n", value, usage->value[0]);
 }
 
+static void pidff_set_period(struct pidff_usage *usage, u16 period)
+{
+	s32 modified_period;
+	modified_period = pidff_rescale_period(period, usage->field);
+	modified_period = pidff_clamp(modified_period, usage->field);
+	usage->value[0] = modified_period;
+}
+
 /*
  * Send envelope report to the device
  */
@@ -392,15 +421,11 @@  static void pidff_set_periodic_report(struct pidff_device *pidff,
 	pidff_set_signed(&pidff->set_periodic[PID_OFFSET],
 			 effect->u.periodic.offset);
 	pidff_set(&pidff->set_periodic[PID_PHASE], effect->u.periodic.phase);
-
-	/* Clamp period to ensure the device can play the effect */
-	pidff->set_periodic[PID_PERIOD].value[0] =
-		pidff_clamp(effect->u.periodic.period,
-			pidff->set_periodic[PID_PERIOD].field);
+	pidff_set_period(&pidff->set_periodic[PID_PERIOD],
+			 effect->u.periodic.period);
 
 	hid_hw_request(pidff->hid, pidff->reports[PID_SET_PERIODIC],
 			HID_REQ_SET_REPORT);
-
 }
 
 /*