media: b2c2: flexcop-usb: fix flexcop_usb_memory_req

BugLink: https://bugs.launchpad.net/bugs/2085849

[ Upstream commit b178aa6f333b07bda0548d7e45085660a112414d ]

smatch generated this warning:

drivers/media/usb/b2c2/flexcop-usb.c:199 flexcop_usb_memory_req() warn: iterator 'i' not incremented

and indeed the function is not using i or updating buf.

The reason this always worked is that this function is called to write just
6 bytes (a MAC address) to the USB device, and so in practice there is only
a single chunk written. If we ever would need to write more than one chunk,
this function would fail since each chunk would read from or write to the
same buf address.

Rewrite the function to properly handle this.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Manuel Diewald <manuel.diewald@canonical.com>
Signed-off-by: Roxana Nicolescu <roxana.nicolescu@canonical.com>

drivers/media/usb/b2c2/flexcop-usb.c

@@ -179,7 +179,7 @@ static int flexcop_usb_memory_req(struct flexcop_usb *fc_usb,
 		flexcop_usb_request_t req, flexcop_usb_mem_page_t page_start,
 		u32 addr, int extended, u8 *buf, u32 len)
 {
-	int i, ret = 0;
+	int ret = 0;
 	u16 wMax;
 	u32 pagechunk = 0;
 
@@ -196,7 +196,7 @@ static int flexcop_usb_memory_req(struct flexcop_usb *fc_usb,
 	default:
 		return -EINVAL;
 	}
-	for (i = 0; i < len;) {
+	while (len) {
 		pagechunk =
 			wMax < bytes_left_to_read_on_page(addr, len) ?
 				wMax :
@@ -209,11 +209,12 @@ static int flexcop_usb_memory_req(struct flexcop_usb *fc_usb,
 			page_start + (addr / V8_MEMORY_PAGE_SIZE),
 			(addr & V8_MEMORY_PAGE_MASK) |
 				(V8_MEMORY_EXTENDED*extended),
-			&buf[i], pagechunk);
+			buf, pagechunk);
 
 		if (ret < 0)
 			return ret;
 		addr += pagechunk;
+		buf += pagechunk;
 		len -= pagechunk;
 	}
 	return 0;