1 files changed, 66 insertions, 24 deletions

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 7e89288..16c2c66 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1075,7 +1075,7 @@ static u32 s32ton(__s32 value, unsigned n)
  * Extract/implement a data field from/to a little endian report (bit array).
  *
  * Code sort-of follows HID spec:
- *     http://www.usb.org/developers/devclass_docs/HID1_11.pdf
+ *     http://www.usb.org/developers/hidpage/HID1_11.pdf
  *
  * While the USB HID spec allows unlimited length bit fields in "report
  * descriptors", most devices never use more than 16 bits.
@@ -1083,20 +1083,37 @@ static u32 s32ton(__s32 value, unsigned n)
  * Search linux-kernel and linux-usb-devel archives for "hid-core extract".
  */
 
-__u32 hid_field_extract(const struct hid_device *hid, __u8 *report,
-		     unsigned offset, unsigned n)
-{
-	u64 x;
+static u32 __extract(u8 *report, unsigned offset, int n)
+{
+	unsigned int idx = offset / 8;
+	unsigned int bit_nr = 0;
+	unsigned int bit_shift = offset % 8;
+	int bits_to_copy = 8 - bit_shift;
+	u32 value = 0;
+	u32 mask = n < 32 ? (1U << n) - 1 : ~0U;
+
+	while (n > 0) {
+		value |= ((u32)report[idx] >> bit_shift) << bit_nr;
+		n -= bits_to_copy;
+		bit_nr += bits_to_copy;
+		bits_to_copy = 8;
+		bit_shift = 0;
+		idx++;
+	}
+
+	return value & mask;
+}
 
-	if (n > 32)
+u32 hid_field_extract(const struct hid_device *hid, u8 *report,
+			unsigned offset, unsigned n)
+{
+	if (n > 32) {
 		hid_warn(hid, "hid_field_extract() called with n (%d) > 32! (%s)\n",
 			 n, current->comm);
+		n = 32;
+	}
 
-	report += offset >> 3;  /* adjust byte index */
-	offset &= 7;            /* now only need bit offset into one byte */
-	x = get_unaligned_le64(report);
-	x = (x >> offset) & ((1ULL << n) - 1);  /* extract bit field */
-	return (u32) x;
+	return __extract(report, offset, n);
 }
 EXPORT_SYMBOL_GPL(hid_field_extract);
 
@@ -1106,31 +1123,56 @@ EXPORT_SYMBOL_GPL(hid_field_extract);
  * The data mangled in the bit stream remains in little endian
  * order the whole time. It make more sense to talk about
  * endianness of register values by considering a register
- * a "cached" copy of the little endiad bit stream.
+ * a "cached" copy of the little endian bit stream.
  */
-static void implement(const struct hid_device *hid, __u8 *report,
-		      unsigned offset, unsigned n, __u32 value)
+
+static void __implement(u8 *report, unsigned offset, int n, u32 value)
+{
+	unsigned int idx = offset / 8;
+	unsigned int size = offset + n;
+	unsigned int bit_shift = offset % 8;
+	int bits_to_set = 8 - bit_shift;
+	u8 bit_mask = 0xff << bit_shift;
+
+	while (n - bits_to_set >= 0) {
+		report[idx] &= ~bit_mask;
+		report[idx] |= value << bit_shift;
+		value >>= bits_to_set;
+		n -= bits_to_set;
+		bits_to_set = 8;
+		bit_mask = 0xff;
+		bit_shift = 0;
+		idx++;
+	}
+
+	/* last nibble */
+	if (n) {
+		if (size % 8)
+			bit_mask &= (1U << (size % 8)) - 1;
+		report[idx] &= ~bit_mask;
+		report[idx] |= (value << bit_shift) & bit_mask;
+	}
+}
+
+static void implement(const struct hid_device *hid, u8 *report,
+		      unsigned offset, unsigned n, u32 value)
 {
-	u64 x;
-	u64 m = (1ULL << n) - 1;
+	u64 m;
 
-	if (n > 32)
+	if (n > 32) {
 		hid_warn(hid, "%s() called with n (%d) > 32! (%s)\n",
 			 __func__, n, current->comm);
+		n = 32;
+	}
 
+	m = (1ULL << n) - 1;
 	if (value > m)
 		hid_warn(hid, "%s() called with too large value %d! (%s)\n",
 			 __func__, value, current->comm);
 	WARN_ON(value > m);
 	value &= m;
 
-	report += offset >> 3;
-	offset &= 7;
-
-	x = get_unaligned_le64(report);
-	x &= ~(m << offset);
-	x |= ((u64)value) << offset;
-	put_unaligned_le64(x, report);
+	__implement(report, offset, n, value);
 }
 
 /*