linux-kernel - Re: [PATCH 6/7] HID: multitouch: append " Pen" to the name of the stylus input

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Date:	Wed, 20 Mar 2013 15:42:27 +0100
From:	Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:	Henrik Rydberg <rydberg@...omail.se>
CC:	Benjamin Tissoires <benjamin.tissoires@...il.com>,
	Jiri Kosina <jkosina@...e.cz>,
	Stephane Chatty <chatty@...c.fr>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/7] HID: multitouch: append " Pen" to the name of the
 stylus input

On 03/19/2013 10:38 PM, Henrik Rydberg wrote:
> Hi Benjamin,
> 
>> This is not just cosmetics, it can help to write udev and X.org
>> rules.
>>
>> Signed-off-by: Benjamin Tissoires <benjamin.tissoires@...hat.com>
>> ---
>>  drivers/hid/hid-multitouch.c | 24 +++++++++++++++++++++++-
>>  1 file changed, 23 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/hid/hid-multitouch.c b/drivers/hid/hid-multitouch.c
>> index d89f0eb..faeec95 100644
>> --- a/drivers/hid/hid-multitouch.c
>> +++ b/drivers/hid/hid-multitouch.c
>> @@ -44,6 +44,7 @@
>>  #include <linux/slab.h>
>>  #include <linux/usb.h>
>>  #include <linux/input/mt.h>
>> +#include <linux/string.h>
>>  
>>  
>>  MODULE_AUTHOR("Stephane Chatty <chatty@...c.fr>");
>> @@ -371,6 +372,15 @@ static int mt_pen_input_mapping(struct hid_device *hdev, struct hid_input *hi,
>>  		unsigned long **bit, int *max)
>>  {
>>  	struct mt_device *td = hid_get_drvdata(hdev);
>> +	char *name;
>> +
>> +	if (hi->input->name == hdev->name) {
>> +		name = kzalloc(sizeof(hdev->name) + 5, GFP_KERNEL);
>> +		if (name) {
>> +			sprintf(name, "%s Pen", hdev->name);
>> +			hi->input->name = name;
>> +		}
>> +	}
> 
> Why not simply duplicate the the string? This kind of magic sharing is
> not really helping.  Also, for multi input devices, the assumptions in
> hidinput_allocate() seem to be the culprit. Perhaps the fix should be
> there instead.

Yes, hidinput_allocate() clearly steals the reference here. However,
fixing this in hid-core would not be simpler: some drivers (ntrig does
at least) assume that there is no need to free input->name, which means
that:
- either we need to fix each individual driver
- either we introduce some kind of mechanism in order not to free "const
char *" declarations like it happens in ntrig.

In v2, I'll just realloc for each input the input->name, and then if the
pen is here, then it will realloc the new name.

Cheers,
Benjamin

> 
>>  
>>  	td->pen_report_id = field->report->id;
>>  
>> @@ -914,6 +924,7 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
>>  	int ret, i;
>>  	struct mt_device *td;
>>  	struct mt_class *mtclass = mt_classes; /* MT_CLS_DEFAULT */
>> +	struct hid_input *hi;
>>  
>>  	for (i = 0; mt_classes[i].name ; i++) {
>>  		if (id->driver_data == mt_classes[i].name) {
>> @@ -964,7 +975,7 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
>>  
>>  	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
>>  	if (ret)
>> -		goto fail;
>> +		goto hid_fail;
>>  
>>  	ret = sysfs_create_group(&hdev->dev.kobj, &mt_attribute_group);
>>  
>> @@ -976,6 +987,10 @@ static int mt_probe(struct hid_device *hdev, const struct hid_device_id *id)
>>  
>>  	return 0;
>>  
>> +hid_fail:
>> +	list_for_each_entry(hi, &hdev->inputs, list)
>> +		if (hi->input->name != hdev->name)
>> +			kfree(hi->input->name);
>>  fail:
>>  	kfree(td->fields);
>>  	kfree(td);
>> @@ -1020,8 +1035,15 @@ static int mt_resume(struct hid_device *hdev)
>>  static void mt_remove(struct hid_device *hdev)
>>  {
>>  	struct mt_device *td = hid_get_drvdata(hdev);
>> +	struct hid_input *hi;
>> +
>>  	sysfs_remove_group(&hdev->dev.kobj, &mt_attribute_group);
>>  	hid_hw_stop(hdev);
>> +
>> +	list_for_each_entry(hi, &hdev->inputs, list)
>> +		if (hi->input->name != hdev->name)
>> +			kfree(hi->input->name);
>> +
>>  	kfree(td);
>>  	hid_set_drvdata(hdev, NULL);
>>  }
>> -- 
>> 1.8.1.2
>>
> 
> Thanks,
> Henrik
> 

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