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    SubjectRe: [PATCH v3] HID: i2c-hid: Ignore input report if there's no data present on Elan touchpanels
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    > On Jan 18, 2019, at 23:50, Benjamin Tissoires <benjamin.tissoires@redhat.com> wrote:
    >
    > Hi Kai-Heng,
    >
    > On Mon, Jan 7, 2019 at 8:24 AM Kai-Heng Feng
    > <kai.heng.feng@canonical.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@canonical.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.

    >
    > 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
    >>

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