HID: cp2112: support large i2c transfers

cp2112_i2c_xfer() only reads up to 61 bytes, returning EIO on longers reads.
The fix is to wrap a loop around cp2112_read() to pick up all the returned
data.

Signed-off-by: Ellen Wang <ellen@cumulusnetworks.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>

1 files changed, 24 insertions, 7 deletions

diff --git a/drivers/hid/hid-cp2112.c b/drivers/hid/hid-cp2112.c
index a2dbbbe0d8d7..75398cb84fde 100644
--- a/drivers/hid/hid-cp2112.c
+++ b/drivers/hid/hid-cp2112.c
@@ -511,13 +511,30 @@ static int cp2112_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
         if (!(msgs->flags & I2C_M_RD))
                 goto finish;
 
-        ret = cp2112_read(dev, msgs->buf, msgs->len);
-        if (ret < 0)
-                goto power_normal;
-        if (ret != msgs->len) {
-                hid_warn(hdev, "short read: %d < %d\n", ret, msgs->len);
-                ret = -EIO;
-                goto power_normal;
+        for (count = 0; count < msgs->len;) {
+                ret = cp2112_read(dev, msgs->buf + count, msgs->len - count);
+                if (ret < 0)
+                        goto power_normal;
+                if (ret == 0) {
+                        hid_err(hdev, "read returned 0\n");
+                        ret = -EIO;
+                        goto power_normal;
+                }
+                count += ret;
+                if (count > msgs->len) {
+                        /*
+                         * The hardware returned too much data.
+                         * This is mostly harmless because cp2112_read()
+                         * has a limit check so didn't overrun our
+                         * buffer.  Nevertheless, we return an error
+                         * because something is seriously wrong and
+                         * it shouldn't go unnoticed.
+                         */
+                        hid_err(hdev, "long read: %d > %zd\n",
+                                ret, msgs->len - count + ret);
+                        ret = -EIO;
+                        goto power_normal;
+                }
         }
 
 finish: