Monday, December 08, 2008

Setting the repeat rate on an input device (Kernel 2.4 and 2.6)

If you ever come into the situation of having to set the repeat delay/period on an input device (/dev/input/eventX), with the additional challenge of needing it to work on both 2.4 and 2.6 kernels, maybe this code snippet might help you (fd is the filedescriptor of the device, opened writable):
        #include <linux/input.h>
struct input_event ie;
ie.type = EV_REP;
ie.code = REP_DELAY;
ie.value = 1000; /* 1 second initial delay */
if (write(fd, &ie, sizeof(ie)) == -1)
ie.code = REP_PERIOD;
ie.value = 250; /* 4 events per second */
if (write(fd, &ie, sizeof(ie)) == -1)

Looks pretty trivial, doesn't it? But it took me quite some time to realize that I needed to write a "magic" event into the device to set the properties ;)

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