From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vaibhav Hiremath Subject: Re: [PATCH v2] HID: cp2112: support large i2c transfers in hid-cp2112 Date: Wed, 08 Jul 2015 17:37:07 +0530 Message-ID: <559D126B.6050505@linaro.org> References: <1436351118-3360-1-git-send-email-ellen@cumulusnetworks.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1436351118-3360-1-git-send-email-ellen-qUQiAmfTcIp+XZJcv9eMoEEOCMrvLtNR@public.gmane.org> Sender: linux-i2c-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Ellen Wang , borneo.antonio-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, dbarksdale-2SNLKkHU5xRBDgjK7y7TUQ@public.gmane.org, jkosina-AlSwsSmVLrQ@public.gmane.org, linux-input-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-input@vger.kernel.org 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 > --- > 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