On Wednesday 08 July 2015 03:55 PM, Ellen Wang wrote:
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@xxxxxxxxxxxxxxxxxxx>
---
This is the updated patch with a check for 0 return from
cp2112_read(). I tested it with a suitable delay in the loop
to trigger the cp2112_raw_event() overrun bug, which must
be fixed before this patch is applied.
---
drivers/hid/hid-cp2112.c | 33 ++++++++++++++++++++++++++-------
1 file changed, 26 insertions(+), 7 deletions(-)
diff --git a/drivers/hid/hid-cp2112.c b/drivers/hid/hid-cp2112.c
index 3318de6..e2ffac0 100644
--- a/drivers/hid/hid-cp2112.c
+++ b/drivers/hid/hid-cp2112.c
@@ -509,13 +509,32 @@ 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);
+ hid_warn(hdev, "read returned %d for %zd\n",
+ ret, msgs->len - count);
Do you always want to throw warning here, unconditionally ?
+ if (ret < 0)
+ goto power_normal;
+ if (ret == 0) {
+ hid_err(hdev, "read returned 0\n");
+ ret = -EIO;
+ goto power_normal;
+ }
bit simplified, I guess :)
if (ret < 0 || ret == 0) {
hid_err(hdev, "read returned %d", ret);
ret = ret == 0 ? -EIO : ret;
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);
You may want to take another look here.
'ret' will be either,
- ret = msgs->len
Not applicable
- ret > msgs->len
(count > msgs->len) will happen in one single
iteration, and will
- ret < msgs->len
(count > msgs->len) will happen in multiple iterations
where count keeps incrementing based on ret
In the 2 scenarios above, I believe you would want to show,
actual read bytes > requested read bytes
Am I missing something here?
Thanks,
Vaibhav
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