On Fri, May 10, 2019 at 01:28:22PM +0200, Petr Štetiar wrote: > Andy Duan <fugang.duan@xxxxxxx> [2019-05-10 08:23:58]: > > Hi Andy, > > you've probably forget to Cc some maintainers and mailing lists, so I'm > adding them now to the Cc loop. This patch series should be posted against > net-next tree as per netdev FAQ[0], but you've to wait little bit as > net-next is currently closed for the new submissions and you would need to > resend it anyway. > > 0. https://www.kernel.org/doc/html/latest/networking/netdev-FAQ.html > > > ethernet controller driver call .of_get_mac_address() to get > > the mac address from devictree tree, if these properties are > > not present, then try to read from nvmem. i.MX6x/7D/8MQ/8MM > > platforms ethernet MAC address read from nvmem ocotp eFuses, > > but it requires to swap the six bytes order. > > Thanks for bringing up this topic, as I would like to extend the > functionality as well, but I'm still unsure how to tackle this and where, > so I'll (ab)use this opportunity to bring other use cases I would like to > cover in the future, so we could better understand the needs. > > This reverse byte order format/layout is one of a few other storage formats > currently used by vendors, some other (creative) vendors are currently > providing MAC addresses in NVMEMs as ASCII text in following two formats > (hexdump -C /dev/mtdX): > > a) 0090FEC9CBE5 - MAC address stored as ASCII without colon between octets > > 00000090 57 2e 4c 41 4e 2e 4d 41 43 2e 41 64 64 72 65 73 |W.LAN.MAC.Addres| > 000000a0 73 3d 30 30 39 30 46 45 43 39 43 42 45 35 00 48 |s=0090FEC9CBE5.H| > 000000b0 57 2e 4c 41 4e 2e 32 47 2e 30 2e 4d 41 43 2e 41 |W.LAN.2G.0.MAC.A| > > (From https://github.com/openwrt/openwrt/pull/1448#issuecomment-442476695) > > b) D4:EE:07:33:6C:20 - MAC address stored as ASCII with colon between octets > > 00000180 66 61 63 5f 6d 61 63 20 3d 20 44 34 3a 45 45 3a |fac_mac = D4:EE:| > 00000190 30 37 3a 33 33 3a 36 43 3a 32 30 0a 42 44 49 4e |07:33:6C:20.BDIN| > > (From https://github.com/openwrt/openwrt/pull/1906#issuecomment-483881911) > > > The patch set is to add property "nvmem_macaddr_swap" to swap > > macaddr bytes order. > > so it would allow following DT construct (simplified): > > ð0 { > nvmem-cells = <ð0_addr>; > nvmem-cell-names = "mac-address"; > nvmem_macaddr_swap; > }; > > I'm not sure about the `nvmem_macaddr_swap` property name, as currently there > are no other properties with underscores, so it should be probably named as > `nvmem-macaddr-swap`. DT specs permits use of the underscores, but the > estabilished convention is probably prefered. > > In order to cover all above mentioned use cases, it would make more sense > to add a description of the MAC address layout to the DT and use this > information to properly postprocess the NVMEM content into usable MAC > address? > > Something like this? > > - nvmem-cells: phandle, reference to an nvmem node for the MAC address > - nvmem-cell-names: string, should be "mac-address" if nvmem is to be used > - nvmem-mac-address-layout: string, specifies MAC address storage layout. > Supported values are: "binary", "binary-swapped", "ascii", "ascii-delimited". > "binary" is the default. > > Or perhaps something like this? > > - nvmem-cells: phandle, reference to an nvmem node for the MAC address > - nvmem-cell-names: string, should be any of the supported values. > Supported values are: "mac-address", "mac-address-swapped", > "mac-address-ascii", "mac-address-ascii-delimited". > > I'm more inclined towards the first proposed solution, as I would like to > propose MAC address octet incrementation feature in the future, so it would > become: > > - nvmem-cells: phandle, reference to an nvmem node for the MAC address > - nvmem-cell-names: string, should be "mac-address" if nvmem is to be used > - nvmem-mac-address-layout: string, specifies MAC address storage layout. > Supported values are: "binary", "binary-swapped", "ascii", "ascii-delimited". > "binary" is the default. > - nvmem-mac-address-increment: number, value by which should be > incremented MAC address octet, could be negative value as well. > - nvmem-mac-address-increment-octet: number, valid values 0-5, default is 5. > Specifies MAC address octet used for `nvmem-mac-address-increment`. > > What do you think? It looks to me that it should be abstracted away by the nvmem interface and done at the provider level, not the customer. Maxime -- Maxime Ripard, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
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