Re: Interacting with a input kernel driver from user space

[Nuno Santos <nsantos@edigma.com>]

On 11/14/2011 06:57 PM, Dmitry Torokhov wrote:
> On Monday, November 14, 2011 10:24:17 AM Nuno Santos wrote:
>> Hi,
>>
>> I have defined my first attribute in the following way:
>>
>> static ssize_t usbtouchscreen_update_sensibility(struct device *dev,
>>                                           struct device_attribute *attr,
>>                                           const char *buf, size_t count)
>> {
>>
>>       printk(KERN_INFO "update sensibility called");
>>
> Updating sensibility is always a good thing but I gather you mean
> sensitivity here...

hahaahha thanks for the correction!!!! I need to do it in several places 
now! :)
>
> BTW this should probably be a per-user setting and belong to the X driver,
> not kernel driver. I.e. kernel streams all data and userspace (X) decides
> what data do discard according to current user preferences.
didn't knew about this capability. but how do you change the settings 
thru X? where can I find the API for that?
>
>>       return 0;
>> }
>>
>> static DEVICE_ATTR(sensibility, 0664, NULL,
>> usbtouchscreen_update_sensibility);
>>
>> static struct attribute *usbtouchscreen_attrs[] = {
>> &dev_attr_sensibility.attr,
>>           NULL
>> };
>>
>> static const struct attribute_group usbtouchscreen_attr_group = {
>>           .attrs = usbtouchscreen_attrs,
>> };
>>
>> In the probe function I have added:
>>
>> if (sysfs_create_group(&intf->dev.kobj,&usbtouchscreen_attr_group))
>>           goto out_unregister_input;
>>
>>
>> Then I tried to write on the attribute in the following way:
>>
>> nsantos@NS-PC:~/workspaces/linux-kernel-driver$ echo 45>
>> /sys/class/input/input7/sensibility
>> bash: /sys/class/input/input7/sensibility: No such file or directory
>>
>> After digging a bit under /sys/class/input/input7 i found that the sub
>> directory device add sensibilty listed so I tried the following:
>>
>> nsantos@NS-PC:~/workspaces/workspace-mtt/linux-kernel-driver$ sudo echo
>> 45>  /sys/class/input/input7/device/sensibility
>> bash: /sys/class/input/input7/device/sensibility: Permission denied
>>
>> With no success again...
>>
>> Am I doing something terribly wrong?
> You aren't doing this as root and don't have permission to access the
> attribute.
sudo doesn't work in this case? Because I was suddoing. if I change the 
attribute to 777 will it be available to everyone? is this a good way of 
doing it?


Sorry for all this questions. Is my first linux driver ever!

Thanks,

With my best regards,

Nuno