HID: google: extract Vivaldi hid feature mapping for use in hid-hammer

We need to support parsing the HID device in both the Vivaldi and the
Hammer drivers so that we can properly expose the function row physmap
to userspace when a hammer device uses a vivaldi keyboard layout for the
function row keys. Extract the feature mapping logic from the vivaldi
driver into an hid specific vivaldi library so we can use it from both
HID drivers.

To allow more code sharing we mandate that vivaldi data must be placed
at the very beginning of the driver data attached to the HID device
instance.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Tested-by: Stephen Boyd <swboyd@chromium.org> # coachz, wormdingler
Link: https://lore.kernel.org/r/20220228075446.466016-4-dmitry.torokhov@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 140 insertions, 0 deletions

diff --git a/drivers/hid/hid-vivaldi-common.c b/drivers/hid/hid-vivaldi-common.c
new file mode 100644
index 000000000000..8b3e515d0f06
--- /dev/null
+++ b/drivers/hid/hid-vivaldi-common.c
@@ -0,0 +1,140 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Helpers for ChromeOS HID Vivaldi keyboards
+ *
+ * Copyright (C) 2022 Google, Inc
+ */
+
+#include <linux/export.h>
+#include <linux/hid.h>
+#include <linux/input/vivaldi-fmap.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/types.h>
+
+#include "hid-vivaldi-common.h"
+
+#define MIN_FN_ROW_KEY 1
+#define MAX_FN_ROW_KEY VIVALDI_MAX_FUNCTION_ROW_KEYS
+#define HID_VD_FN_ROW_PHYSMAP 0x00000001
+#define HID_USAGE_FN_ROW_PHYSMAP (HID_UP_GOOGLEVENDOR | HID_VD_FN_ROW_PHYSMAP)
+
+/**
+ * vivaldi_feature_mapping - Fill out vivaldi keymap data exposed via HID
+ * @hdev: HID device to parse
+ * @field: HID field to parse
+ * @usage: HID usage to parse
+ *
+ * Note: this function assumes that driver data attached to @hdev contains an
+ * instance of &struct vivaldi_data at the very beginning.
+ */
+void vivaldi_feature_mapping(struct hid_device *hdev,
+			     struct hid_field *field, struct hid_usage *usage)
+{
+	struct vivaldi_data *data = hid_get_drvdata(hdev);
+	struct hid_report *report = field->report;
+	u8 *report_data, *buf;
+	u32 report_len;
+	unsigned int fn_key;
+	int ret;
+
+	if (field->logical != HID_USAGE_FN_ROW_PHYSMAP ||
+	    (usage->hid & HID_USAGE_PAGE) != HID_UP_ORDINAL)
+		return;
+
+	fn_key = usage->hid & HID_USAGE;
+	if (fn_key < MIN_FN_ROW_KEY || fn_key > MAX_FN_ROW_KEY)
+		return;
+
+	if (fn_key > data->num_function_row_keys)
+		data->num_function_row_keys = fn_key;
+
+	report_data = buf = hid_alloc_report_buf(report, GFP_KERNEL);
+	if (!report_data)
+		return;
+
+	report_len = hid_report_len(report);
+	if (!report->id) {
+		/*
+		 * hid_hw_raw_request() will stuff report ID (which will be 0)
+		 * into the first byte of the buffer even for unnumbered
+		 * reports, so we need to account for this to avoid getting
+		 * -EOVERFLOW in return.
+		 * Note that hid_alloc_report_buf() adds 7 bytes to the size
+		 * so we can safely say that we have space for an extra byte.
+		 */
+		report_len++;
+	}
+
+	ret = hid_hw_raw_request(hdev, report->id, report_data,
+				 report_len, HID_FEATURE_REPORT,
+				 HID_REQ_GET_REPORT);
+	if (ret < 0) {
+		dev_warn(&hdev->dev, "failed to fetch feature %d\n",
+			 field->report->id);
+		goto out;
+	}
+
+	if (!report->id) {
+		/*
+		 * Undo the damage from hid_hw_raw_request() for unnumbered
+		 * reports.
+		 */
+		report_data++;
+		report_len--;
+	}
+
+	ret = hid_report_raw_event(hdev, HID_FEATURE_REPORT, report_data,
+				   report_len, 0);
+	if (ret) {
+		dev_warn(&hdev->dev, "failed to report feature %d\n",
+			 field->report->id);
+		goto out;
+	}
+
+	data->function_row_physmap[fn_key - MIN_FN_ROW_KEY] =
+		field->value[usage->usage_index];
+
+out:
+	kfree(buf);
+}
+EXPORT_SYMBOL_GPL(vivaldi_feature_mapping);
+
+static ssize_t function_row_physmap_show(struct device *dev,
+					 struct device_attribute *attr,
+					 char *buf)
+{
+	struct hid_device *hdev = to_hid_device(dev);
+	struct vivaldi_data *data = hid_get_drvdata(hdev);
+
+	return vivaldi_function_row_physmap_show(data, buf);
+}
+
+static DEVICE_ATTR_RO(function_row_physmap);
+static struct attribute *vivaldi_sysfs_attrs[] = {
+	&dev_attr_function_row_physmap.attr,
+	NULL
+};
+
+static const struct attribute_group vivaldi_attribute_group = {
+	.attrs = vivaldi_sysfs_attrs,
+};
+
+/**
+ * vivaldi_input_configured - Complete initialization of device using vivaldi map
+ * @hdev: HID device to which vivaldi attributes should be attached
+ * @hidinput: HID input device (unused)
+ */
+int vivaldi_input_configured(struct hid_device *hdev,
+			     struct hid_input *hidinput)
+{
+	struct vivaldi_data *data = hid_get_drvdata(hdev);
+
+	if (!data->num_function_row_keys)
+		return 0;
+
+	return devm_device_add_group(&hdev->dev, &vivaldi_attribute_group);
+}
+EXPORT_SYMBOL_GPL(vivaldi_input_configured);
+
+MODULE_LICENSE("GPL");