How to read and interpret /dev/cpu_dma_latency?

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Issue

Reading /dev/cpu_dma_latency from userspace / user mode is not clarified in kernel sources in 'Documentation/power/pm_qos_interface.txt'
reading /dev/cpu_dma_latency prints gibberish

# cat /dev/cpu_dma_latency
�5w

Environment

Red Hat Enterprise Linux 7

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