linux-kernel - Re: [PATCH v3] HID: i2c-hid: Ignore input report if there's no data present on Elan touchpanels

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Message-Id: <D83049E7-8AE2-4C80-B160-5F35BB8170EE@canonical.com>
Date:   Wed, 30 Jan 2019 11:50:54 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Jiri Kosina <jikos@...nel.org>,
        "open list:HID CORE LAYER" <linux-input@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] HID: i2c-hid: Ignore input report if there's no data
 present on Elan touchpanels



> On Jan 29, 2019, at 18:05, Benjamin Tissoires <benjamin.tissoires@...hat.com> wrote:
> 
> On Mon, Jan 21, 2019 at 4:30 AM Kai-Heng Feng
> <kai.heng.feng@...onical.com> wrote:
>> 
>> 
>> 
>>> On Jan 18, 2019, at 23:50, Benjamin Tissoires <benjamin.tissoires@...hat.com> wrote:
>>> 
>>> Hi Kai-Heng,
>>> 
>>> On Mon, Jan 7, 2019 at 8:24 AM Kai-Heng Feng
>>> <kai.heng.feng@...onical.com> wrote:
>>>> 
>>>> While using Elan touchpads, the message floods:
>>>> [  136.138487] i2c_hid i2c-DELL08D6:00: i2c_hid_get_input: incomplete report (14/65535)
>>>> 
>>>> Though the message flood is annoying, the device it self works without
>>>> any issue. I suspect that the device in question takes too much time to
>>>> pull the IRQ back to high after I2C host has done reading its data.
>>>> 
>>>> Since the host receives all useful data, let's ignore the input report
>>>> when there's no data.
>>>> 
>>>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
>>> 
>>> Thanks for the v3.
>>> 
>>> This patch has just been brought to my attention, and I have one
>>> question before applying it:
>>> are those messages (without your patch) occurring all the time, or
>>> just after resume?
>> 
>> All the time.
>> 
>> The touchpad works fine though. The entire report is 0xff, so it can be
>> safely ignored.
> 
> Couple of things:
> - I have forgotten to tell you that I have applied this patch in
> for-5.1/i2c-hid, it will be pushed to linux-next today.

Thanks!

> - Dell told me that a BIOS fix was solving the issue. We can still
> quarry the patch, but there should not be a strong need for it when
> users upgrade their BIOS.

Multiple platforms are affected by this issue [1], so the patch can still be really helpful.

[1] https://bugs.launchpad.net/bugs/1784152

Kai-Heng

> 
> Cheers,
> Benjamin
> 
>> 
>>> 
>>> I wonder if the pm_suspend delay we talked about in the other thread
>>> would fix that issue in a cleaner way.
>> 
>> I’ve replied in another thread, unfortunately it can’t.
>> 
>> We can introduce msleep() between each commands though, but I don’t
>> think it’s good either.
>> 
>> Kai-Heng
>> 
>>> 
>>> Cheers,
>>> Benjamin
>>> 
>>>> ---
>>>> v3:
>>>> Fix compiler error/warnings.
>>>> 
>>>> v2:
>>>> Use dev_warn_once() to warn the user about the situation.
>>>> 
>>>> drivers/hid/i2c-hid/i2c-hid-core.c | 9 +++++++++
>>>> 1 file changed, 9 insertions(+)
>>>> 
>>>> diff --git a/drivers/hid/i2c-hid/i2c-hid-core.c b/drivers/hid/i2c-hid/i2c-hid-core.c
>>>> index 8555ce7e737b..2f940c1de616 100644
>>>> --- a/drivers/hid/i2c-hid/i2c-hid-core.c
>>>> +++ b/drivers/hid/i2c-hid/i2c-hid-core.c
>>>> @@ -50,6 +50,7 @@
>>>> #define I2C_HID_QUIRK_NO_IRQ_AFTER_RESET       BIT(1)
>>>> #define I2C_HID_QUIRK_NO_RUNTIME_PM            BIT(2)
>>>> #define I2C_HID_QUIRK_DELAY_AFTER_SLEEP                BIT(3)
>>>> +#define I2C_HID_QUIRK_BOGUS_IRQ                        BIT(4)
>>>> 
>>>> /* flags */
>>>> #define I2C_HID_STARTED                0
>>>> @@ -179,6 +180,8 @@ static const struct i2c_hid_quirks {
>>>>               I2C_HID_QUIRK_DELAY_AFTER_SLEEP },
>>>>       { USB_VENDOR_ID_LG, I2C_DEVICE_ID_LG_8001,
>>>>               I2C_HID_QUIRK_NO_RUNTIME_PM },
>>>> +       { USB_VENDOR_ID_ELAN, HID_ANY_ID,
>>>> +                I2C_HID_QUIRK_BOGUS_IRQ },
>>>>       { 0, 0 }
>>>> };
>>>> 
>>>> @@ -503,6 +506,12 @@ static void i2c_hid_get_input(struct i2c_hid *ihid)
>>>>               return;
>>>>       }
>>>> 
>>>> +       if (ihid->quirks & I2C_HID_QUIRK_BOGUS_IRQ && ret_size == 0xffff) {
>>>> +               dev_warn_once(&ihid->client->dev, "%s: IRQ triggered but "
>>>> +                             "there's no data\n", __func__);
>>>> +               return;
>>>> +       }
>>>> +
>>>>       if ((ret_size > size) || (ret_size < 2)) {
>>>>               dev_err(&ihid->client->dev, "%s: incomplete report (%d/%d)\n",
>>>>                       __func__, size, ret_size);
>>>> --
>>>> 2.17.1