KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 156 insertions, 0 deletions

diff --git a/drivers/hid/hid-lgff.c b/drivers/hid/hid-lgff.c
new file mode 100644
index 000000000..aed4ddc39
--- /dev/null
+++ b/drivers/hid/hid-lgff.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Force feedback support for hid-compliant for some of the devices from
+ * Logitech, namely:
+ * - WingMan Cordless RumblePad
+ * - WingMan Force 3D
+ *
+ *  Copyright (c) 2002-2004 Johann Deneux
+ *  Copyright (c) 2006 Anssi Hannula <anssi.hannula@gmail.com>
+ */
+
+/*
+ *
+ * Should you need to contact me, the author, you can do so by
+ * e-mail - mail your message to <johann.deneux@it.uu.se>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/input.h>
+#include <linux/hid.h>
+
+#include "hid-lg.h"
+
+struct dev_type {
+	u16 idVendor;
+	u16 idProduct;
+	const signed short *ff;
+};
+
+static const signed short ff_rumble[] = {
+	FF_RUMBLE,
+	-1
+};
+
+static const signed short ff_joystick[] = {
+	FF_CONSTANT,
+	-1
+};
+
+static const signed short ff_joystick_ac[] = {
+	FF_CONSTANT,
+	FF_AUTOCENTER,
+	-1
+};
+
+static const struct dev_type devices[] = {
+	{ 0x046d, 0xc211, ff_rumble },
+	{ 0x046d, 0xc219, ff_rumble },
+	{ 0x046d, 0xc283, ff_joystick },
+	{ 0x046d, 0xc286, ff_joystick_ac },
+	{ 0x046d, 0xc287, ff_joystick_ac },
+	{ 0x046d, 0xc293, ff_joystick },
+	{ 0x046d, 0xc295, ff_joystick },
+};
+
+static int hid_lgff_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;
+	unsigned int left, right;
+
+#define CLAMP(x) if (x < 0) x = 0; if (x > 0xff) x = 0xff
+
+	switch (effect->type) {
+	case FF_CONSTANT:
+		x = effect->u.ramp.start_level + 0x7f;	/* 0x7f is center */
+		y = effect->u.ramp.end_level + 0x7f;
+		CLAMP(x);
+		CLAMP(y);
+		report->field[0]->value[0] = 0x51;
+		report->field[0]->value[1] = 0x08;
+		report->field[0]->value[2] = x;
+		report->field[0]->value[3] = y;
+		dbg_hid("(x, y)=(%04x, %04x)\n", x, y);
+		hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+		break;
+
+	case FF_RUMBLE:
+		right = effect->u.rumble.strong_magnitude;
+		left = effect->u.rumble.weak_magnitude;
+		right = right * 0xff / 0xffff;
+		left = left * 0xff / 0xffff;
+		CLAMP(left);
+		CLAMP(right);
+		report->field[0]->value[0] = 0x42;
+		report->field[0]->value[1] = 0x00;
+		report->field[0]->value[2] = left;
+		report->field[0]->value[3] = right;
+		dbg_hid("(left, right)=(%04x, %04x)\n", left, right);
+		hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+		break;
+	}
+	return 0;
+}
+
+static void hid_lgff_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);
+	__s32 *value = report->field[0]->value;
+	magnitude = (magnitude >> 12) & 0xf;
+	*value++ = 0xfe;
+	*value++ = 0x0d;
+	*value++ = magnitude;   /* clockwise strength */
+	*value++ = magnitude;   /* counter-clockwise strength */
+	*value++ = 0x80;
+	*value++ = 0x00;
+	*value = 0x00;
+	hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+}
+
+int lgff_init(struct hid_device* hid)
+{
+	struct hid_input *hidinput;
+	struct input_dev *dev;
+	const signed short *ff_bits = ff_joystick;
+	int error;
+	int i;
+
+	if (list_empty(&hid->inputs)) {
+		hid_err(hid, "no inputs found\n");
+		return -ENODEV;
+	}
+	hidinput = list_entry(hid->inputs.next, struct hid_input, list);
+	dev = hidinput->input;
+
+	/* Check that the report looks ok */
+	if (!hid_validate_values(hid, HID_OUTPUT_REPORT, 0, 0, 7))
+		return -ENODEV;
+
+	for (i = 0; i < ARRAY_SIZE(devices); i++) {
+		if (dev->id.vendor == devices[i].idVendor &&
+		    dev->id.product == devices[i].idProduct) {
+			ff_bits = devices[i].ff;
+			break;
+		}
+	}
+
+	for (i = 0; ff_bits[i] >= 0; i++)
+		set_bit(ff_bits[i], dev->ffbit);
+
+	error = input_ff_create_memless(dev, NULL, hid_lgff_play);
+	if (error)
+		return error;
+
+	if ( test_bit(FF_AUTOCENTER, dev->ffbit) )
+		dev->ff->set_autocenter = hid_lgff_set_autocenter;
+
+	pr_info("Force feedback for Logitech force feedback devices by Johann Deneux <johann.deneux@it.uu.se>\n");
+
+	return 0;
+}