[openwrt/openwrt] rockchip: use alternative CID path

[LEDE Commits]

blocktrron pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/eb85ab9ab6a1dbd81103a2d3243e893de3680bf9

commit eb85ab9ab6a1dbd81103a2d3243e893de3680bf9
Author: David Bauer <mail at david-bauer.net>
AuthorDate: Sat Apr 17 20:32:57 2021 +0200

    rockchip: use alternative CID path
    
    Use an alternative path to access the CID of the SD card in MMC0, used
    for the generation of MAC addresses. With Kernel 5.10, the device name
    of the MMC controller changed, breaking MAC address generation.
    
    The new path is compatible with Kernel 5.4 as well as Kernel 5.10.
    
    Signed-off-by: David Bauer <mail at david-bauer.net>
---
 target/linux/rockchip/armv8/base-files/etc/board.d/02_network | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/linux/rockchip/armv8/base-files/etc/board.d/02_network b/target/linux/rockchip/armv8/base-files/etc/board.d/02_network
index 99f55513aa..f5e88cc148 100644
--- a/target/linux/rockchip/armv8/base-files/etc/board.d/02_network
+++ b/target/linux/rockchip/armv8/base-files/etc/board.d/02_network
@@ -18,7 +18,7 @@ rockchip_setup_interfaces()
 
 nanopi_r2s_generate_mac()
 {
-	local sd_hash=$(sha256sum /sys/devices/platform/ff500000.dwmmc/mmc_host/mmc0/mmc0:*/cid)
+	local sd_hash=$(sha256sum /sys/class/block/mmcblk0/device/cid)
 	local mac_base=$(macaddr_canonicalize "$(echo "${sd_hash}" | dd bs=1 count=12 2>/dev/null)")
 	echo "$(macaddr_unsetbit_mc "$(macaddr_setbit_la "${mac_base}")")"
 }