HID: Add HID Report Descriptor to sysfs

Add a new binary sysfs entry called report_descriptor which contains
the HID report descriptor.

Signed-off-by: Alan Ott <alan@signal11.us>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

2 files changed, 43 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-driver-hid b/Documentation/ABI/testing/sysfs-driver-hid
new file mode 100644
index 000000000000..b6490e14fe83
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-driver-hid
@@ -0,0 +1,10 @@
+What:           For USB devices : /sys/bus/usb/devices/<busnum>-<devnum>:<config num>.<interface num>/<hid-bus>:<vendor-id>:<product-id>.<num>/report_descriptor
+                For BT devices  : /sys/class/bluetooth/hci<addr>/<hid-bus>:<vendor-id>:<product-id>.<num>/report_descriptor
+                Symlink         : /sys/class/hidraw/hidraw<num>/device/report_descriptor
+Date:           Jan 2011
+KernelVersion:  2.0.39
+Contact:        Alan Ott <alan@signal11.us>
+Description:    When read, this file returns the device's raw binary HID
+                report descriptor.
+                This file cannot be written.
+Users:          HIDAPI library (http://www.signal11.us/oss/hidapi)
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 2dcdf9ff02ea..5e0e4eea7065 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1159,6 +1159,32 @@ static bool hid_hiddev(struct hid_device *hdev)
         return !!hid_match_id(hdev, hid_hiddev_list);
 }
 
+
+static ssize_t
+read_report_descriptor(struct file *filp, struct kobject *kobj,
+                struct bin_attribute *attr,
+                char *buf, loff_t off, size_t count)
+{
+        struct device *dev = container_of(kobj, struct device, kobj);
+        struct hid_device *hdev = container_of(dev, struct hid_device, dev);
+
+        if (off >= hdev->rsize)
+                return 0;
+
+        if (off + count > hdev->rsize)
+                count = hdev->rsize - off;
+
+        memcpy(buf, hdev->rdesc + off, count);
+
+        return count;
+}
+
+static struct bin_attribute dev_bin_attr_report_desc = {
+        .attr = { .name = "report_descriptor", .mode = 0444 },
+        .read = read_report_descriptor,
+        .size = HID_MAX_DESCRIPTOR_SIZE,
+};
+
 int hid_connect(struct hid_device *hdev, unsigned int connect_mask)
 {
         static const char *types[] = { "Device", "Pointer", "Mouse", "Device",
@@ -1169,6 +1195,7 @@ int hid_connect(struct hid_device *hdev, unsigned int connect_mask)
         char buf[64];
         unsigned int i;
         int len;
+        int ret;
 
         if (hdev->quirks & HID_QUIRK_HIDDEV_FORCE)
                 connect_mask |= (HID_CONNECT_HIDDEV_FORCE | HID_CONNECT_HIDDEV);
@@ -1230,6 +1257,11 @@ int hid_connect(struct hid_device *hdev, unsigned int connect_mask)
                 bus = "<UNKNOWN>";
         }
 
+        ret = device_create_bin_file(&hdev->dev, &dev_bin_attr_report_desc);
+        if (ret)
+                hid_warn(hdev,
+                         "can't create sysfs report descriptor attribute err: %d\n", ret);
+
         hid_info(hdev, "%s: %s HID v%x.%02x %s [%s] on %s\n",
                  buf, bus, hdev->version >> 8, hdev->version & 0xff,
                  type, hdev->name, hdev->phys);
@@ -1240,6 +1272,7 @@ EXPORT_SYMBOL_GPL(hid_connect);
 
 void hid_disconnect(struct hid_device *hdev)
 {
+        device_remove_bin_file(&hdev->dev, &dev_bin_attr_report_desc);
         if (hdev->claimed & HID_CLAIMED_INPUT)
                 hidinput_disconnect(hdev);
         if (hdev->claimed & HID_CLAIMED_HIDDEV)