При таком вызове: sudo strace -e fault=write:when=5 sh -c "echo 's 3 1000 800' > /sys/class/drm/card1/device/pp_od_clk_voltage"
получаю:
...
openat(AT_FDCWD, "/sys/class/drm/card1/device/pp_od_clk_voltage", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 3
fcntl(1, F_DUPFD, 10) = 10
close(1) = 0
fcntl(10, F_SETFD, FD_CLOEXEC) = 0
dup2(3, 1) = 1
close(3) = 0
write(1, "s 3 1000 800\n", 13) = 0
write(1, "s 3 1000 800\n", 13) = 0
write(1, "s 3 1000 800\n", 13) = 0
write(1, "s 3 1000 800\n", 13) = 0
write(1, "s 3 1000 800\n", 13) = -1 ENOSYS (Функция не реализована) (INJECTED)
write(2, "sh: 1: echo: ", 13sh: 1: echo: ) = 13
write(2, "echo: I/O error", 15echo: I/O error) = 15
write(2, "\n", 1
) = 1
dup2(10, 1) = 1
close(10) = 0
exit_group(1) = ?
+++ exited with 1 +++
Пнёте в нужном направлении?