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 <20180928170818.32124-1-jekarlson@gmail.com> <84a0aba3-0793-1659-c70c-d5ece650f832@collabora.com>
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From:   Benson Leung <bleung@chromium.org>
Date:   Tue, 9 Oct 2018 20:44:12 -0700
Message-ID: <CANLzEkt4FBZDSTiZqJNkKDFLojMtayVAgusg764nhOcpCDmSOQ@mail.gmail.com>
Subject: Re: [PATCH] mfd: cros-ec: copy the whole event in get_next_event_xfer
To:     Enric Balletbo i Serra <enric.balletbo@collabora.com>
Cc:     jekarlson@gmail.com, kernel@esmil.dk,
        Neil Armstrong <narmstrong@baylibre.com>,
        Stefan Adolfsson <sadolfsson@chromium.org>,
        Lee Jones <lee.jones@linaro.org>,
        Olof Johansson <olof@lixom.net>,
        Linux Kernel <linux-kernel@vger.kernel.org>
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Hi Enric,
On Wed, Oct 3, 2018 at 4:01 AM Enric Balletbo i Serra
<enric.balletbo@collabora.com> wrote:
>
> Hi Emil,
>
> Many thanks to catch this and fix. Some comments below.
>
> You missed to add the v2, please send the next patch with v3 prefix.
>
> On 28/9/18 19:08, Emil Karlson wrote:
> > Commit 57e94c8b974db2d83c60e1139c89a70806abbea0 caused cros-ec keyboard events
> > be truncated on many chromebooks so that Left and Right keys on Column 12 were
> > always 0. Use ret as memcpy len to fix this.
> >
>
> That's fine
>
> > drivers/platform/chrome/cros_ec_proto.c:509
> > get_next_event_xfer uses ret from cros_ec_cmd_xfer for memcpy for msg->data len
> > drivers/platform/chrome/cros_ec_proto.c:445
> > cros_ec_cmd_xfer gets ret from send_command
> > drivers/platform/chrome/cros_ec_proto.c:93
> > send_command gets ret from bus specific xfer_fn
> > drivers/mfd/cros_ec_spi.c:598
> > cros_ec_cmd_xfer_spi copies len amount to ec_msg->data and returns len as ret
> > drivers/mfd/cros_ec_i2c.c:267
> > cros_ec_cmd_xfer_i2c copies len amount to ec_msg->data and returns len as ret
> >
> > so msg->data length is always the same as ret.
> >
>
> Instead of describe the different calls involved and the returns. I'd explain
> why using ret fixes the issue.
>
> > Fixes: 57e94c8b974d ("mfd: cros-ec: Increase maximum mkbp event size")
> > Signed-off-by: Emil Karlson <jekarlson@gmail.com>
> > ---
> >  drivers/platform/chrome/cros_ec_proto.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> > index 398393ab5df8..b6fd4838f60f 100644
> > --- a/drivers/platform/chrome/cros_ec_proto.c
> > +++ b/drivers/platform/chrome/cros_ec_proto.c
> > @@ -520,7 +520,7 @@ static int get_next_event_xfer(struct cros_ec_device *ec_dev,
> >       ret = cros_ec_cmd_xfer(ec_dev, msg);
> >       if (ret > 0) {
> >               ec_dev->event_size = ret - 1;
> > -             memcpy(&ec_dev->event_data, msg->data, ec_dev->event_size);
> > +             memcpy(&ec_dev->event_data, msg->data, ret);
> >       }
> >
> >       return ret;
> >
>
> After thinking a bit more on this I think that how you fixed this is really
> clear. I was wondering if the downstream solution would be better but as is
> really late and will be good have this as urgent fix for the coming release I am
> happy with it. We can always send follow up patches to sync with the downstream
> version if is preferred.
>
> Neil, can you give us your Tested-by to have the make sure this doesn't break
> with protocol v1, I don't have such hardware.
>
> Benson, will be really good have this merged in this rc. Are you fine with this
> solution?

Yes, I'm fine with it. Let me get this ready and try to get it before
we run out of rcs of 4.19.

>
> BTW, you can add my in next version.
>
> Acked-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>


-- 
Benson Leung
Staff Software Engineer
Chrome OS Kernel
Google Inc.
bleung@google.com
Chromium OS Project
bleung@chromium.org