Can't get file to copy from /sys/ on rooted Android
Files in /sys/ are part of sysfs which is a special virtual filesystem to dialog with the Linux kernel.

You can for example have a fast introduction here.

Therefore you cannot treat sysfs files as normal files as it may lead to strange behaviour depending on how the program treats them (same for device files, usually in /dev, or files in procfs in /proc). 

Usually to tweak that files you just write in them with an echo, such as

echo 255 &gt; /sys/class/leds/mmc1::/max_brightness