HID: support primax keyboards violating USB HID spec

Primax keyboards with the issue this driver addresses report modifier
keys as in band key events instead of as out of band modifier bits,
resulting in the modifier keys generating key up events immediately
before the keys they are intended to modify.  This driver rewrites
the raw report data from such keyboards into USB HID 1.11 compliant
report data.  It only matches the USB vendor and product IDs for the
keyboard it has been tested on. Since there are several keyboards,
notably a number of laptops and folding USB keyboards known to have
similar unresolved problem reports, the list is expected to grow.

Signed-off-by: Terry Lambert <tlambert@chromium.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

1 files changed, 117 insertions, 0 deletions

diff --git a/drivers/hid/hid-primax.c b/drivers/hid/hid-primax.c
new file mode 100644
index 000000000000..4d3c60d88318
--- /dev/null
+++ b/drivers/hid/hid-primax.c
@@ -0,0 +1,117 @@
+/*
+ * HID driver for primax and similar keyboards with in-band modifiers
+ *
+ * Copyright 2011 Google Inc. All Rights Reserved
+ *
+ * Author:
+ *      Terry Lambert <tlambert@google.com>
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+static int px_raw_event(struct hid_device *hid, struct hid_report *report,
+         u8 *data, int size)
+{
+        int idx = size;
+
+        switch (report->id) {
+        case 0:         /* keyboard input */
+                /*
+                 * Convert in-band modifier key values into out of band
+                 * modifier bits and pull the key strokes from the report.
+                 * Thus a report data set which looked like:
+                 *
+                 * [00][00][E0][30][00][00][00][00]
+                 * (no modifier bits + "Left Shift" key + "1" key)
+                 *
+                 * Would be converted to:
+                 *
+                 * [01][00][00][30][00][00][00][00]
+                 * (Left Shift modifier bit + "1" key)
+                 *
+                 * As long as it's in the size range, the upper level
+                 * drivers don't particularly care if there are in-band
+                 * 0-valued keys, so they don't stop parsing.
+                 */
+                while (--idx > 1) {
+                        if (data[idx] < 0xE0 || data[idx] > 0xE7)
+                                continue;
+                        data[0] |= (1 << (data[idx] - 0xE0));
+                        data[idx] = 0;
+                }
+                hid_report_raw_event(hid, HID_INPUT_REPORT, data, size, 0);
+                return 1;
+
+        default:        /* unknown report */
+                /* Unknown report type; pass upstream */
+                hid_info(hid, "unknown report type %d\n", report->id);
+                break;
+        }
+
+        return 0;
+}
+
+static int px_probe(struct hid_device *hid, const struct hid_device_id *id)
+{
+        int ret;
+
+        ret = hid_parse(hid);
+        if (ret) {
+                hid_err(hid, "parse failed\n");
+                goto fail;
+        }
+
+        ret = hid_hw_start(hid, HID_CONNECT_DEFAULT);
+        if (ret)
+                hid_err(hid, "hw start failed\n");
+
+fail:
+        return ret;
+}
+
+static void px_remove(struct hid_device *hid)
+{
+        hid_hw_stop(hid);
+}
+
+static const struct hid_device_id px_devices[] = {
+        { HID_USB_DEVICE(USB_VENDOR_ID_PRIMAX, USB_DEVICE_ID_PRIMAX_KEYBOARD) },
+        { }
+};
+MODULE_DEVICE_TABLE(hid, px_devices);
+
+static struct hid_driver px_driver = {
+        .name = "primax",
+        .id_table = px_devices,
+        .raw_event = px_raw_event,
+        .probe = px_probe,
+        .remove = px_remove,
+};
+
+static int __init px_init(void)
+{
+        return hid_register_driver(&px_driver);
+}
+
+static void __exit px_exit(void)
+{
+        hid_unregister_driver(&px_driver);
+}
+
+module_init(px_init);
+module_exit(px_exit);
+MODULE_AUTHOR("Terry Lambert <tlambert@google.com>");
+MODULE_LICENSE("GPL");