Re: git: 920518cf2e75 - main - FDT: implement fdt_ether_get_addr()

Hi,

Nice work! I like the usage of ether_gen_addr for user friendliness when no MAC is known.

I did some work on ether_gen_addr in the past and back then I had a situation that an ifp was not (yet) available so I added ether_gen_addr_byname. Somebody (I can look it up if needed) agreed on this and said that ether_gen_addr using ifp is actually a layering violation.
So you might take a look if it is easy to pass in the interface name and call ether_gen_addr_byname instead of using the ifp.

Regards,
Ronald.

 
Van: Michal Meloun <mmel@FreeBSD.org>
Datum: maandag, 13 juli 2026 10:36
Aan: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org
Onderwerp: git: 920518cf2e75 - main - FDT: implement fdt_ether_get_addr()
> 
> The branch main has been updated by mmel:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=920518cf2e75012135104886d92814c048baa2fb
> 
> commit 920518cf2e75012135104886d92814c048baa2fb
> Author:     Michal Meloun <mmel@FreeBSD.org>
> AuthorDate: 2026-07-13 08:34:22 +0000
> Commit:     Michal Meloun <mmel@FreeBSD.org>
> CommitDate: 2026-07-13 08:35:47 +0000
> 
>     FDT: implement fdt_ether_get_addr()
>     
>     Introduce fdt_ether_get_addr() in fdt_common.c/h that tries standard
>     DT properties in the correct order and falls back to a random address
>     when needed. This should be used by ethernet drivers instead of open-coding
>     the same logic.
>     
>     MFC after:      2 weeks
>     
>     Reviewed by:    mhorne, adrian, bz, jrtc27
>     Differential Revision:  https://reviews.freebsd.org/D58104
> ---
>  sys/dev/fdt/fdt_common.c | 40 ++++++++++++++++++++++++++++++++++++++++
>  sys/dev/fdt/fdt_common.h |  4 ++++
>  2 files changed, 44 insertions(+)
> 
> diff --git a/sys/dev/fdt/fdt_common.c b/sys/dev/fdt/fdt_common.c
> index f43551c6310e..93897b598b30 100644
> --- a/sys/dev/fdt/fdt_common.c
> +++ b/sys/dev/fdt/fdt_common.c
> @@ -553,3 +553,43 @@ fdt_get_chosen_bootargs(char *bootargs, size_t max_size)
>         return (ENXIO);
>     return (0);
>  }
> +
> +/*
> + * fdt_ether_get_addr - Get ethernet MAC address using FDT properties.
> + * Order:
> + *   1. "mac-address"
> + *   2. "local-mac-address"
> + *   3. Keep pre-initialized value (if valid)
> + *   4. random ether_gen_addr() as last resort
> + */
> +void
> +fdt_ether_get_addr(phandle_t node, struct ifnet *ifp, uint8_t *eaddr)
> +{
> +   uint8_t tmp[ETHER_ADDR_LEN];
> +   int len;
> +
> +   /* Firstly try "mac-address" */
> +   len = OF_getprop(node, "mac-address", tmp, sizeof(tmp));
> +   if (len == ETHER_ADDR_LEN && !ETHER_IS_ZERO(tmp) &&
> +       !ETHER_IS_MULTICAST(tmp)) {
> +       bcopy(tmp, eaddr, ETHER_ADDR_LEN);
> +       return;
> +   }
> +
> +   /* Next use  "local-mac-address" */
> +   len = OF_getprop(node, "local-mac-address", tmp, sizeof(tmp));
> +   if (len == ETHER_ADDR_LEN && !ETHER_IS_ZERO(tmp) &&
> +       !ETHER_IS_MULTICAST(tmp)) {
> +       bcopy(tmp, eaddr, ETHER_ADDR_LEN);
> +       return;
> +   }
> +
> +   /* Next use existing one if set */
> +   if (!ETHER_IS_ZERO(eaddr) && !ETHER_IS_MULTICAST(eaddr))
> +       return;
> +
> +   /* Last resort - generate random one */
> +   ether_gen_addr(ifp, (struct ether_addr *)eaddr);
> +
> +   return;
> +}
> diff --git a/sys/dev/fdt/fdt_common.h b/sys/dev/fdt/fdt_common.h
> index f597233f9771..3eee6913ad72 100644
> --- a/sys/dev/fdt/fdt_common.h
> +++ b/sys/dev/fdt/fdt_common.h
> @@ -33,8 +33,11 @@
>  
>  #include <sys/sysctl.h>
>  #include <sys/slicer.h>
> +#include <sys/socket.h>
>  #include <contrib/libfdt/libfdt_env.h>
>  #include <dev/ofw/ofw_bus.h>
> +#include <net/ethernet.h>
> +#include <net/if.h>
>  
>  #define FDT_MEM_REGIONS    64
>  
> @@ -70,6 +73,7 @@ typedef void (*fdt_mem_region_cb)(const struct mem_region *, void *);
>  int fdt_addrsize_cells(phandle_t, int *, int *);
>  u_long fdt_data_get(const void *, int);
>  int fdt_data_to_res(const pcell_t *, int, int, u_long *, u_long *);
> +void fdt_ether_get_addr(phandle_t node, struct ifnet *ifp, uint8_t *eaddr);
>  phandle_t fdt_find_compatible(phandle_t, const char *, int);
>  phandle_t fdt_depth_search_compatible(phandle_t, const char *, int);
>  int fdt_foreach_mem_region(fdt_mem_region_cb, void *);
>  
> 
> 
>