Hi Nuno On Mon, Nov 14, 2011 at 5:31 PM, Nuno Santos <nsantos@xxxxxxxxxx> wrote: > On 11/14/2011 04:09 PM, David Herrmann wrote: >>> I need to be able to communicate to and from the device from the an >>> application build in Qt. So, there must be something really generic that >>> I >>> can call from the application environment. In windows I use window API to >>> call IOCTLS interaction. >> >> Why? I thought this thing is an input device? Why does an application >> have to modify a running device? Is this modification local to the >> application<->device interface or does it also affect all other >> running applications that use this device? > > Yes, it is an multitouch overlay input device. However all the processing is > done on the host side. The device delivers raw data into the system and all > the tracking and touch information is processed on the kernel side. The > control panel for this device shows the input data and permits some > parameter change. In order to visualize that data I need to be able to get a > complete structure from it. When I change a parameter it will reflect the > change to the input being reported to all the applications that use that > input device. The most straightforward approach would be applying default values I think. If there is still a need to have variable configuration values you should use sysfs attributes here. Maybe Dmitry knows other generic ways in the input layer, but I would recommend sysfs attributes here. This is never wrong ;) >> If it is a configuration value to put the device into a different >> state or similar, then you can use a sysfs attribute. The user can >> change this with "echo<value> >/sys/class/input/inputX/<attribute>" > > For setting new simple values I see I can use this interface, but two > questions arise. How can I send a structure with this interface? Can I fopen > this sys file and send the whole structure thru this mechanism. What about > receiving data from the device? sysfs attributes are simple files. That is, you can write to and read from them. Please see ./Documentation/driver-model/device.txt for a rough overview. You basically register two callbacks: read and write. The read callback is called when userspace reads the file. You should then pass the requested data to userspace. The write callback is called when userspace writes the file. You should parse the data and modify your internal structures accordingly. But please take into account that you should never use a single attribute for multiple values. If you need to pass a structure to the driver then register multiple attributes, one for each member of the structure. It is *not* bad style to have several attributes. If there are possible race-conditions if a structure is not passed atomically, you may violate this rule in some places. Almost every driver today registers several attributes so it shouldn't be hard to find examples. > Regards, > > Nuno Regards David -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
