HID: uhid: Add UHID_CREATE2 + UHID_INPUT2

UHID_CREATE2:
HID report descriptor data (rd_data) is an array in struct uhid_create2_req,
instead of a pointer. Enables use from languages that don't support pointers,
e.g. Python.

UHID_INPUT2:
Data array is the last field of struct uhid_input2_req. Enables userspace to
write only the required bytes to kernel (ev.type + ev.u.input2.size + the part
of the data array that matters), instead of the entire struct uhid_input2_req.

Note:
UHID_CREATE2 increases the total size of struct uhid_event slightly, thus
increasing the size of messages that are queued for userspace. However, this
won't affect the userspace processing of these events.

[Jiri Kosina <[e-mail]>: adjust to hid_get_raw_report() and
hid_output_raw_report() API changes]

Signed-off-by: Petri Gynther <[e-mail]>
Reviewed-by: David Herrmann <[e-mail]>
Signed-off-by: Jiri Kosina <[e-mail]>

Documentation/hid/uhid.txt

···
   event to the kernel. The payload is of type struct uhid_create_req and
   contains information about your device. You can start I/O now.
 
+  UHID_CREATE2:
+  Same as UHID_CREATE, but the HID report descriptor data (rd_data) is an array
+  inside struct uhid_create2_req, instead of a pointer to a separate array.
+  Enables use from languages that don't support pointers, e.g. Python.
+
   UHID_DESTROY:
   This destroys the internal HID device. No further I/O will be accepted. There
   may still be pending messages that you can receive with read() but no further
···
   You must send UHID_CREATE before sending input to the kernel! This event
   contains a data-payload. This is the raw data that you read from your device.
   The kernel will parse the HID reports and react on it.
+
+  UHID_INPUT2:
+  Same as UHID_INPUT, but the data array is the last field of uhid_input2_req.
+  Enables userspace to write only the required bytes to kernel (ev.type +
+  ev.u.input2.size + the part of the data array that matters), instead of
+  the entire struct uhid_input2_req.
 
   UHID_FEATURE_ANSWER:
   If you receive a UHID_FEATURE request you must answer with this request. You

drivers/hid/uhid.c

···
 	return ret;
 }
 
+static int uhid_dev_create2(struct uhid_device *uhid,
+			    const struct uhid_event *ev)
+{
+	struct hid_device *hid;
+	int ret;
+
+	if (uhid->running)
+		return -EALREADY;
+
+	uhid->rd_size = ev->u.create2.rd_size;
+	if (uhid->rd_size <= 0 || uhid->rd_size > HID_MAX_DESCRIPTOR_SIZE)
+		return -EINVAL;
+
+	uhid->rd_data = kmalloc(uhid->rd_size, GFP_KERNEL);
+	if (!uhid->rd_data)
+		return -ENOMEM;
+
+	memcpy(uhid->rd_data, ev->u.create2.rd_data, uhid->rd_size);
+
+	hid = hid_allocate_device();
+	if (IS_ERR(hid)) {
+		ret = PTR_ERR(hid);
+		goto err_free;
+	}
+
+	strncpy(hid->name, ev->u.create2.name, 127);
+	hid->name[127] = 0;
+	strncpy(hid->phys, ev->u.create2.phys, 63);
+	hid->phys[63] = 0;
+	strncpy(hid->uniq, ev->u.create2.uniq, 63);
+	hid->uniq[63] = 0;
+
+	hid->ll_driver = &uhid_hid_driver;
+	hid->bus = ev->u.create2.bus;
+	hid->vendor = ev->u.create2.vendor;
+	hid->product = ev->u.create2.product;
+	hid->version = ev->u.create2.version;
+	hid->country = ev->u.create2.country;
+	hid->driver_data = uhid;
+	hid->dev.parent = uhid_misc.this_device;
+
+	uhid->hid = hid;
+	uhid->running = true;
+
+	ret = hid_add_device(hid);
+	if (ret) {
+		hid_err(hid, "Cannot register HID device\n");
+		goto err_hid;
+	}
+
+	return 0;
+
+err_hid:
+	hid_destroy_device(hid);
+	uhid->hid = NULL;
+	uhid->running = false;
+err_free:
+	kfree(uhid->rd_data);
+	return ret;
+}
+
 static int uhid_dev_destroy(struct uhid_device *uhid)
 {
 	if (!uhid->running)
···
 
 	hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input.data,
 			 min_t(size_t, ev->u.input.size, UHID_DATA_MAX), 0);
+
+	return 0;
+}
+
+static int uhid_dev_input2(struct uhid_device *uhid, struct uhid_event *ev)
+{
+	if (!uhid->running)
+		return -EINVAL;
+
+	hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input2.data,
+			 min_t(size_t, ev->u.input2.size, UHID_DATA_MAX), 0);
 
 	return 0;
 }
···
 	case UHID_CREATE:
 		ret = uhid_dev_create(uhid, &uhid->input_buf);
 		break;
+	case UHID_CREATE2:
+		ret = uhid_dev_create2(uhid, &uhid->input_buf);
+		break;
 	case UHID_DESTROY:
 		ret = uhid_dev_destroy(uhid);
 		break;
 	case UHID_INPUT:
 		ret = uhid_dev_input(uhid, &uhid->input_buf);
+		break;
+	case UHID_INPUT2:
+		ret = uhid_dev_input2(uhid, &uhid->input_buf);
 		break;
 	case UHID_FEATURE_ANSWER:
 		ret = uhid_dev_feature_answer(uhid, &uhid->input_buf);

include/uapi/linux/uhid.h

···
 
 #include <linux/input.h>
 #include <linux/types.h>
+#include <linux/hid.h>
 
 enum uhid_event_type {
 	UHID_CREATE,
···
 	UHID_INPUT,
 	UHID_FEATURE,
 	UHID_FEATURE_ANSWER,
+	UHID_CREATE2,
+	UHID_INPUT2,
 };
 
 struct uhid_create_req {
···
 	__u32 country;
 } __attribute__((__packed__));
 
+struct uhid_create2_req {
+	__u8 name[128];
+	__u8 phys[64];
+	__u8 uniq[64];
+	__u16 rd_size;
+	__u16 bus;
+	__u32 vendor;
+	__u32 product;
+	__u32 version;
+	__u32 country;
+	__u8 rd_data[HID_MAX_DESCRIPTOR_SIZE];
+} __attribute__((__packed__));
+
 #define UHID_DATA_MAX 4096
 
 enum uhid_report_type {
···
 struct uhid_input_req {
 	__u8 data[UHID_DATA_MAX];
 	__u16 size;
+} __attribute__((__packed__));
+
+struct uhid_input2_req {
+	__u16 size;
+	__u8 data[UHID_DATA_MAX];
 } __attribute__((__packed__));
 
 struct uhid_output_req {
···
 		struct uhid_output_ev_req output_ev;
 		struct uhid_feature_req feature;
 		struct uhid_feature_answer_req feature_answer;
+		struct uhid_create2_req create2;
+		struct uhid_input2_req input2;
 	} u;
 } __attribute__((__packed__));