unix: add HIDRAW ioctls

This change adds (most) of the ioctl API for the Linux HIDRAW interface.
Reading and writing non-numbered HID reports is done using the read and
write system calls respectively.

Some of the HIDIOC* request numbers are exported directly while others
are kept unexported. This is because some of the #defines require a len
attribute that doesn't have a specific well defined value.

Wrapper types are added for most of the request numbers as is standard.
No wrapper is added for HIDIOCGRDESCSIZE as it would just be
IoctlGetUint32.

The HIDIOC[GS]FEATURE, HIDIOC[GS]INPUT and HIDIOC[GS]OUTPUT request
numbers, which are required for numbered HID reports, are entirely
ommitted as the len attribute has to be a runtime variable. These could
be added later by doing something like
 `HIDIOCGFEATURE(0) | (len << _IOC_SIZESHIFT)`,
with care taken that len doesn't overflow _IOC_XSIZEMASK.

Outdated documentation for the HIDRAW interface is available at:
https://www.kernel.org/doc/Documentation/hid/hidraw.txt.

Change-Id: I2ae5060f0f46150f6fb52959c2e55f50927c1f69
Reviewed-on: https://go-review.googlesource.com/c/sys/+/289169
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>

unix/zerrors_linux.go

@@ -245,6 +245,10 @@ const (
 	BS0                                         = 0x0
 	BTRFS_SUPER_MAGIC                           = 0x9123683e
 	BTRFS_TEST_MAGIC                            = 0x73727279
+	BUS_BLUETOOTH                               = 0x5
+	BUS_HIL                                     = 0x4
+	BUS_USB                                     = 0x3
+	BUS_VIRTUAL                                 = 0x6
 	CAN_BCM                                     = 0x2
 	CAN_EFF_FLAG                                = 0x80000000
 	CAN_EFF_ID_BITS                             = 0x1d
@@ -964,6 +968,7 @@ const (
 	HDIO_SET_XFER                               = 0x306
 	HDIO_TRISTATE_HWIF                          = 0x31b
 	HDIO_UNREGISTER_HWIF                        = 0x32a
+	HID_MAX_DESCRIPTOR_SIZE                     = 0x1000
 	HOSTFS_SUPER_MAGIC                          = 0xc0ffee
 	HPFS_SUPER_MAGIC                            = 0xf995e849
 	HUGETLBFS_MAGIC                             = 0x958458f6
@@ -2736,6 +2741,9 @@ const (
 	Z3FOLD_MAGIC                                = 0x33
 	ZONEFS_MAGIC                                = 0x5a4f4653
 	ZSMALLOC_MAGIC                              = 0x58295829
+	_HIDIOCGRAWNAME_LEN                         = 0x80
+	_HIDIOCGRAWPHYS_LEN                         = 0x40
+	_HIDIOCGRAWUNIQ_LEN                         = 0x40
 )
 
 // Errors