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

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Date:   Fri, 28 Dec 2018 23:58:07 +0800
From:   Kai Heng Feng <kai.heng.feng@...onical.com>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     benjamin.tissoires@...hat.com, linux-input@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] HID: i2c-hid: Ignore input report if there's no data
 present on Elan touchpanels



> On Dec 19, 2018, at 21:09, Jiri Kosina <jikos@...nel.org> wrote:
> 
> On Fri, 14 Dec 2018, Kai-Heng Feng 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.
> 
> Interesting, never seen such a bug before.
> 
>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
>> ---
>> 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..1776afa6d69c 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_dbg(&ihid->client->dev,
>> +			"%s: IRQ triggered but there's no data\n", __func__);
>> +		return;
>> +	}
> 
> Would it perhaps make sense to make this some sort of printk_once(), so 
> that it's immediately apparent from dmesg that the system/device is 
> suffering from this particular problem? Might potentially be helpful piece 
> of information.

Good advice, I’ll send a v2 patch to address this issue.

Kai-Heng

> 
> Thanks,
> 
> -- 
> Jiri Kosina
> SUSE Labs
>