On Thu, 1 Oct 2020 at 10:36, Lukasz Stelmach [off-list ref] wrote:

It was <2020-10-01 czw 09:22>, when Krzysztof Kozlowski wrote:

quoted

On Wed, Sep 30, 2020 at 04:31:51PM +0200, Łukasz Stelmach wrote:

quoted

Add a placeholder for a MAC address. A bootloader may fill it
to set the MAC address and override EEPROM settings.

Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
---
 arch/arm/boot/dts/exynos5422-odroidxu3.dts | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/arm/boot/dts/exynos5422-odroidxu3.dts b/arch/arm/boot/dts/exynos5422-odroidxu3.dts
index db0bc17a667b..9f7f3eacb750 100644
--- a/arch/arm/boot/dts/exynos5422-odroidxu3.dts
+++ b/arch/arm/boot/dts/exynos5422-odroidxu3.dts

@@ -70,3 +70,21 @@ &pwm {
 &usbdrd_dwc3_1 {
     dr_mode = "peripheral";
 };
+
+&usbhost2 {
+    #address-cells = <1>;
+    #size-cells = <0>;
+
+    hub@1 {
+            compatible = "usb8087,0024";
+            reg = <1>;
+            #address-cells = <1>;
+            #size-cells = <0>;
+
+            ethernet: usbether@1 {
+                    compatible = "usb0c45,6310";
+                    reg = <1>;
+                    mac-address = [00 00 00 00 00 00]; /* Filled in by a bootloader */

Why do you need a placeholder? U-Boot can just append the
address/property.

Several other dts files have such placeholder

git grep 'mac-addr.*\[00 00 00 00 00 00\]' arch/arm/boot/dts/ | wc -l
26

Yeah, but if this is cargo cult, then it is not a good reason. First of all,
git grep '[^-]mac-addr.*\[.*00 00 00 00 00 00.*\]' arch/arm/boot/dts/
gives just seven boards. Not a big number to make a standard. :)

The meaning of mac-address, I think, is not a placeholder, but:
"should be used in cases where the MAC address assigned to the device
by the boot program is different from the local-mac-address property."

I think you actually wanted a local-mac-address and the majority of
DTSes use it. Not mac-address.

I can see two scenarios where this patch may be helpful. Another
(simple) boot loading code might be used.

OK, good point. However other bootloader still has to adhere to the DT
specification and the bindings.

The value may also be
customized during build time and used without any support of a
bootloader.

Yes, with an overlay. You do not need a placeholder for this and
actually having a placeholder instead of using overlays is the wrong
approach for customization of boots/builds.

Finding and filling a placeholder would be easier in u-boot too.

U-Boot already has the code for updating mac-address or
local-mac-address so how is it easier for him? You mean that it cannot
find an ethernet node here?

And it serves as a reference how to configure a USB device in a dts

Great places for references are examples in bindings.

Best regards,
Krzysztof

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel