On Tue, Dec 7, 2010 at 13:40, Arnd Bergmann <arnd@xxxxxxxx> wrote: > On Tuesday 07 December 2010, Kay Sievers wrote: >> On Tue, Dec 7, 2010 at 10:16, Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx> wrote: >> > Hi Henrik, >> > >> > On Tue, Dec 07, 2010 at 08:25:26AM +0100, Henrik Rydberg wrote: >> >> Today, userspace sets up an input device based on the data it emits. >> >> This is not always enough; a tablet and a touchscreen may emit exactly >> >> the same data, for instance, but the former should be set up with a >> >> pointer whereas the latter does not need to. Recently, a new type of >> >> touchpad has emerged where the buttons are under the pad, which changes >> >> handling logic without changing the emitted data. This patch introduces >> >> a new ioctl, EVIOCGDEVINFO, which allows userspace to extract information >> >> about the device resulting in proper setup. >> > >> > If we agree that the new ioctl is suitable we'llalso need to wireit up >> > through sysfs. Also, can we keep all definitions to INPUT_ namespace? >> >> Please don't add new ioctls which are not extensible. The ioctl should >> carry the length or the version of the structure it asks for, so it >> can be extended in the future. Sysfs should be good enough for such >> interface though. > > Please never add any ioctls that have a version or length field! > > Ideally ioctls should have only scalar arguments, not structures, > so I'd recommend splitting it into two, so you can read type and > capability parameters separately. Please don't add new ioctls with a single value only. :) That's what sysfs is for, today. The problem is that sysfs or ioctls with a single value can not handle atomic queries of multiple values, and (rightfully) needing that in some cases is a reason to add an ioctl() instead of sysfs. Kay -- 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
