Initial commit

Makefile

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+# Comment/uncomment the following line to disable/enable debugging
+# DEBUG = y
+MODULE_NAME = hid-acer-one
+KVER = $(shell uname -r)
+MODDESTDIR = /lib/modules/$(KVER)/kernel/drivers/hid/
+
+# Add your debugging flag (or not) to CFLAGS
+ifeq ($(DEBUG),y)
+  DEBFLAGS = -O -g -DSHORT_DEBUG # "-O" is needed to expand inlines
+else
+  DEBFLAGS = -O2
+endif
+
+ccflags-y += $(DEBFLAGS)
+
+ifneq ($(KERNELRELEASE),)
+# call from kernel build system
+
+obj-m	:= hid-acer-one.o
+
+else
+
+KERNELDIR ?= /lib/modules/$(KVER)/build
+PWD       := $(shell pwd)
+
+default:
+	$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
+
+endif
+
+
+clean:
+	rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions
+
+depend .depend dep:
+	$(CC) $(CFLAGS) -M *.c > .depend
+
+install:
+	install -p -m 644 $(MODULE_NAME).ko  $(MODDESTDIR)
+	/sbin/depmod -a ${KVER}
+
+uninstall:
+	rm -f $(MODDESTDIR)/$(MODULE_NAME).ko
+	/sbin/depmod -a ${KVER}
+
+ifeq (.depend,$(wildcard .depend))
+include .depend
+endif

README.md

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+# Overview of the error
+Some Acer keyboards report excessively large max usage values. This causes an error at boot which leaves the keyboard inoperable; since the max use values in the report descriptor exceed HID_MAX_USAGES the descriptor isn't parsed.
+
+This module simply changes the report descriptor to have more sensible max usage values during boot before passing the edited version up to the generic hid module for parsing.
+
+##### Known keyboards with this issue
+* `06CB:73F4` (This is the only one targeted by this fix at present)
+* `06CB:2968`
+* `06CB:2991`
+    
+This module specifically targets keyboards identifying themsleves as ` 06CB:73F4 `. If your device identifies itself as `06CB:2968` or `06CB:2991` they should work OOTB on Linux Kernels version 4.3 and above, for older kernels the fix (which this module was adapted from) can be found [here](https://github.com/SWW13/hid-acer).
+
+#### Symptoms of the error
+
+Symptoms that this might be a problem you are experiencing is a message along the lines of `hid (null): usage index exceeded` followed by hid-generic complaining that `parsing failed` in your dmesg logs.
+
+## Build / Install
+First install linux-headers for your version of Linux, some details can be found [here](http://www.cyberciti.biz/tips/build-linux-kernel-module-against-installed-kernel-source-tree.html).
+
+```
+git clone https://github.com/BradyMcD/hid-acer-one.git
+cd hid-acer-one
+make
+sudo make install
+```
+
+#### Uninstall
+```
+sudo make uninstall
+```

acer-hids.h

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+#ifndef ACER_HIDS
+#define ACER_HIDS
+
+#define USB_VENDOR_ID_ACER_SYNAPTICS	0x06cb
+#define USB_VENDOR_ID_ACER_SYNAPTICS_TP_73F4    0x73F4
+
+#endif//ACER_HIDS

hid-acer-one.c

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+/*
+ *  HID driver for acer devices
+ *
+ *  Copyright (c) 2016 Brady McDonough
+ *  Modified from Simon Wörner's hid-acer <https://github.com/SWW13/hid-acer>
+ */
+
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "acer-hids.h"
+
+/* Some Acer keyboards have an issue where they report an excessive max usages value
+ * The kyboard targeted in this fix identifies itself as 06CB:73F4
+ *
+ * At boot this module pre-parses the report descriptor and changes the values so that they will parse properly
+ */
+
+#define ACER_KBD_RDESC_ORIG_SIZE	188
+#define ACER_KBD_RDESC_CHECK_POS	(173 * sizeof(__u8))
+#define ACER_KBD_RDESC_CHECK_DATA	0x2AFFFF150026FFFF
+#define ACER_KBD_RDESC_FIX_POS1		ACER_KBD_RDESC_CHECK_POS + 2
+#define ACER_KBD_RDESC_FIX_POS2		ACER_KBD_RDESC_CHECK_POS + 7
+
+static __u8 *acer_kbd_report_fixup(struct hid_device *hdev, __u8 *rdesc, unsigned int *rsize){
+
+  /* Check that we are looking at the same correct descirptor */
+  if (*rsize == ACER_KBD_RDESC_ORIG_SIZE) {
+    __u64 check = be64_to_cpu(*(__be64 *)(rdesc + ACER_KBD_RDESC_CHECK_POS));
+    
+    /* check for invalid max usages */
+    if (check == ACER_KBD_RDESC_CHECK_DATA) {
+      hid_info(hdev, "fixing up acer keyboard report descriptor\n");
+      
+      /* change max values to 0xFF00 */
+      rdesc[ACER_KBD_RDESC_FIX_POS1] = 0x00;
+      rdesc[ACER_KBD_RDESC_FIX_POS2] = 0x00;
+    }
+  }
+  
+  return rdesc;
+}
+
+static const struct hid_device_id acer_devices[] = {
+  { HID_USB_DEVICE(USB_VENDOR_ID_ACER_SYNAPTICS,
+		   USB_VENDOR_ID_ACER_SYNAPTICS_TP_73F4) },
+  { }
+};
+MODULE_DEVICE_TABLE(hid, acer_devices);
+
+static struct hid_driver acer_driver = {
+  .name = "acer",
+  .id_table = acer_devices,
+  .report_fixup = acer_kbd_report_fixup,
+};
+module_hid_driver(acer_driver);
+
+MODULE_AUTHOR("Brady McDonough");
+MODULE_LICENSE("GPL");