Hi Andrew, [CCing David Herrmann] On Sun, 25 November 2012 Andrew de los Reyes wrote: > Benjamin Tissoires and Nestor Lopez Casado have been helping me to add > Linux support for new Logitech Touch Mice (T620, T400). After running > into a road-block in hid-core, and solving it with this patch, we > thought it was good to show the community and see if this is okay, or > if there's a better solution that we've missed. > > Thanks for your comments, > -andrew > > This patch separates struct hid_device's driver_lock into two. The > goal is to allow hid device drivers to receive input during their > probe() function call. This is necessary because some drivers need to > communicate with the device to determine parameters needed during > probe (e.g., size of a multi-touch surface). > > Historically, three functions used driver_lock: > > - hid_device_probe: blocks to acquire lock > - hid_device_remove: blocks to acquire lock > - hid_input_report: if locked returns -EBUSY, else acquires lock > > This patch adds another lock (driver_input_lock) which is used to > block input from occurring. The lock behavior is now: > > - hid_device_probe: blocks to acq. driver_lock, then driver_input_lock > - hid_device_remove: blocks to acq. driver_lock, then driver_input_lock > - hid_input_report: if driver_input_lock locked returns -EBUSY, else > acquires driver_input_lock > > This results in no behavior change for existing devices and > drivers. However, during a probe() function call in a driver, that > driver may now selectively unlock driver_input_lock to let input > events come through, then re-lock. That is more or less a new approach to release the restriction added in commit 4ea5454203d991ec85264f64f89ca8855fce69b0 (HID: Fix race condition between driver core and ll-driver). >From your suggested change the question could be if releasing the input lock should be connected to hw_start() / hw_stop() calls... Though connecting those together would certainly require some review of existing drivers in order not to reopen the can of worms closed by above mentioned commit. Bruno -- 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
