[PATCH 1/9] Bluetooth: HIDP: Fix GET_REPORT and SET_REPORT for unnumbered reports

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

Internally, the kernel HID subsystem expects that report buffers for
both numbered and unnumbered raw report requests begin with a report ID
byte, using report ID 0 for unnumbered reports.

Adjust Bluetooth HIDP transport callbacks to adhere to this convention.
When fetching an unnumbered report, request the report without a report
ID over the control channel, prepend the report ID 0 byte to the
received data, and account for it in the returned length. Similarly,
when setting an unnumbered report, strip the leading dummy report ID
before sending the transfer while including it in the reported transfer
count.

Fixes: 0a7f364e8122 ("HID: Add the transport-driver functions to the HIDP driver.")
Assisted-by: LLM
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 net/bluetooth/hidp/core.c | 29 +++++++++++++++++++++++------
 1 file changed, 23 insertions(+), 6 deletions(-)

diff --git a/net/bluetooth/hidp/core.c b/net/bluetooth/hidp/core.c
index f5bdf9f1ca63..004a8eed51fb 100644
--- a/net/bluetooth/hidp/core.c
+++ b/net/bluetooth/hidp/core.c
@@ -248,7 +248,6 @@ static int hidp_get_raw_report(struct hid_device *hid,
 	struct hidp_session *session = hid->driver_data;
 	struct sk_buff *skb;
 	size_t len;
-	int numbered_reports = hid->report_enum[report_type].numbered;
 	int ret;
 
 	if (atomic_read(&session->terminate))
@@ -273,10 +272,11 @@ static int hidp_get_raw_report(struct hid_device *hid,
 
 	/* Set up our wait, and send the report request to the device. */
 	session->waiting_report_type = report_type & HIDP_DATA_RTYPE_MASK;
-	session->waiting_report_number = numbered_reports ? report_number : -1;
+	session->waiting_report_number = report_number ? report_number : -1;
 	set_bit(HIDP_WAITING_FOR_RETURN, &session->flags);
+
 	data[0] = report_number;
-	ret = hidp_send_ctrl_message(session, report_type, data, 1);
+	ret = hidp_send_ctrl_message(session, report_type, data, !!report_number);
 	if (ret < 0)
 		goto err;
 
@@ -302,11 +302,25 @@ static int hidp_get_raw_report(struct hid_device *hid,
 		}
 	}
 
+	/*
+	 * In case of unnumbered reports the response from the device will
+	 * not have the report ID that the upper layers expect, so we need
+	 * to stash it in the buffer ourselves and adjust the data size.
+	 */
+	if (!report_number) {
+		data[0] = 0;
+		data++;
+		count--;
+	}
+
 	skb = session->report_return;
 	if (skb) {
-		len = skb->len < count ? skb->len : count;
+		len = min_t(size_t, skb->len, count);
 		memcpy(data, skb->data, len);
 
+		if (!report_number && len)
+			len++;
+
 		kfree_skb(skb);
 		session->report_return = NULL;
 	} else {
@@ -350,9 +364,12 @@ static int hidp_set_raw_report(struct hid_device *hid, unsigned char reportnum,
 		return -ERESTARTSYS;
 
 	/* Set up our wait, and send the report request to the device. */
-	data[0] = reportnum;
+	if (reportnum)
+		data[0] = reportnum;
+
 	set_bit(HIDP_WAITING_FOR_SEND_ACK, &session->flags);
-	ret = hidp_send_ctrl_message(session, report_type, data, count);
+	ret = hidp_send_ctrl_message(session, report_type,
+				     data + !reportnum, count - !reportnum);
 	if (ret < 0)
 		goto err;
 

-- 
2.56.0.385.gd3acb90ef8-goog