Re: [PATCH 2/4] hid-lenovo: Add support for X1 Tablet cover LED control

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Hi Jiri,

Thanks for your comments. I added comments in-lined.

Best regards,

Dennis

On 19.12.2016 10:54, Jiri Kosina wrote:
> Hi Dennis,
> 
> thanks a lot for the patch.
> 
> On Fri, 9 Dec 2016, Dennis Wassenberg wrote:
> 
>> +int hid_lenovo_led_set(enum hid_lenovo_led_type led, bool on)
>> +{
>> +	struct led_classdev *dev = NULL;
>> +	struct lenovo_led_list_entry *entry;
>> +
>> +	if (led >= HID_LENOVO_LED_MAX)
>> +		return -EINVAL;
>> +
>> +	hid_lenovo_initial_leds[led] = on ? LED_FULL : LED_OFF;
>> +
>> +	list_for_each_entry(entry, &hid_lenovo_leds, list) {
>> +		if (entry->type == led) {
>> +			dev = entry->dev;
>> +			break;
>> +		}
>> +	}
> 
> How exactly is this synchronized against lenovo_remove_tpx1cover()?
> 
In case of that the tpx1cover is disconnected it will be removed from hid_lenovo_leds list. That means not included at the hid_lenovo_leds list. In this case dev is still NULL and the function will return -ENODEV. The static array hid_lenovo_initial_leds is still set to store the current state of a LED type. This is used to set the LED appropriately if the tpx1cover is replugged.

Maybe I should add a mutex to protect the hid_lenovo_leds list operations in hid-lenovo.c to fix the case if a unplug occurred concurrently to setting an led?!

>> +
>> +	if (!dev)
>> +		return -ENODEV;
>> +
>> +	if (!dev->brightness_set)
>> +		return -ENODEV;
>> +
>> +	dev->brightness_set(dev, on ? LED_FULL : LED_OFF);
>> +
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(hid_lenovo_led_set);
> 
> Does this really need to be exported to the whole universe? (I guess this 
> will be further discussed in 4/4).

No, it is sufficient if thinkpad-helper can access it.
> 
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