linux-kernel - Re: [PATCH v10 52/55] input: touchscreen: atmel_mxt_ts: Added sysfs entry for touchscreen status

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Message-ID: <1ea292db-d0c3-935e-e74c-7b4afe251edc@mentor.com>
Date:   Wed, 1 Apr 2020 21:51:28 +0900
From:   "Wang, Jiada" <jiada_wang@...tor.com>
To:     Dmitry Osipenko <digetx@...il.com>, <nick@...anahar.org>,
        <dmitry.torokhov@...il.com>, <jikos@...nel.org>,
        <benjamin.tissoires@...hat.com>, <bsz@...ihalf.com>
CC:     <linux-input@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <erosca@...adit-jv.com>, <Andrew_Gabbasov@...tor.com>
Subject: Re: [PATCH v10 52/55] input: touchscreen: atmel_mxt_ts: Added sysfs
 entry for touchscreen status

Hi Dmitry

Thanks for your comments

On 2020/04/01 0:08, Dmitry Osipenko wrote:
> 31.03.2020 13:50, Jiada Wang пишет:
> ...
>> +static void mxt_watchdog_work(struct work_struct *work)
>> +{
>> +	struct mxt_data *data =
>> +		container_of(work, struct mxt_data, watchdog_work.work);
>> +	u16 info_buf;
>> +	int ret;
>> +
>> +	if (data->suspended || data->in_bootloader ||
>> +	    data->mxt_status.intp_triggered)
>> +		goto sched_work;
> 
> Won't it become a problem if other thread puts device into suspended /
> bootloader state in the same time?
> 
right, I will use mutex lock to prevent such case.
also I think data->mxt_status.intp_triggered isn't necessary,
when lock is used.

>> +	ret = __mxt_read_reg(data->client, 0, sizeof(info_buf), &info_buf);
>> +
>> +	if (ret) {
>> +		data->mxt_status.error_count++;
>> +		data->mxt_status.dev_status = false;
>> +	} else {
>> +		data->mxt_status.dev_status = true;
>> +	}
>> +
>> +sched_work:
>> +	schedule_delayed_work(&data->watchdog_work,
>> +			      msecs_to_jiffies(MXT_WATCHDOG_TIMEOUT));
>> +}
> ...
> 
>> @@ -4329,6 +4390,12 @@ static int mxt_probe(struct i2c_client *client, const struct i2c_device_id *id)
>>   		msleep(MXT_RESET_TIME);
>>   	}
>>   
>> +	if (debug_state) {
>> +		INIT_DELAYED_WORK(&data->watchdog_work, mxt_watchdog_work);
>> +		schedule_delayed_work(&data->watchdog_work,
>> +				      msecs_to_jiffies(MXT_WATCHDOG_TIMEOUT));
>> +	}
>> +
>>   	error = mxt_initialize(data);
>>   	if (error)
>>   		goto err_free_object;
>> @@ -4343,6 +4410,8 @@ static int mxt_probe(struct i2c_client *client, const struct i2c_device_id *id)
>>   	return 0;
>>   
>>   err_free_object:
>> +	if (debug_state)
>> +		cancel_delayed_work_sync(&data->watchdog_work);
>>   	mxt_free_input_device(data);
>>   	mxt_free_object_table(data);
>>   	if (data->reset_gpio) {
>> @@ -4367,6 +4436,9 @@ static int mxt_remove(struct i2c_client *client)
>>   	mxt_free_input_device(data);
>>   	mxt_free_object_table(data);
>>   
>> +	if (debug_state)
>> +		cancel_delayed_work_sync(&data->watchdog_work);
> 
> What will happen if debug_state was false during of mxt_probe() and then
> the debug_state parameter was changed to true via sysfs?

module_param debug_state is added with permission 0,
so it's value won't change during driver operation
> 
> I think the INIT_DELAYED_WORK() and cancel_delayed_work_sync() should be
> invoked unconditionally.
> 
>>   	return 0;
>>   }
>>   
>> @@ -4463,3 +4535,7 @@ module_i2c_driver(mxt_driver);
>>   MODULE_AUTHOR("Joonyoung Shim <jy0922.shim@...sung.com>");
>>   MODULE_DESCRIPTION("Atmel maXTouch Touchscreen driver");
>>   MODULE_LICENSE("GPL");
>> +
>> +module_param(debug_state, bool, 0);
>> +MODULE_PARM_DESC(debug_state, "Enable/Disable watchdog work to check device state (default="
>> +		 __MODULE_STRING(MXT_DEBUG_STATE) ")");
>>
> 
> The "default=..." part of MODULE_PARM_DESC() probably isn't really
> useful and could be omitted, don't you think so?
> 
since debug_state can't be updated via sysfs, so I think add it's 
default in MODULE_PARM_DESC() is useful? what's your opinion?

Thanks,
Jiada