linux-kernel - Re: [PATCH v3] of/fdt: Rework early_init_dt_scan

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Date:   Wed, 15 Dec 2021 08:16:28 -0600
From:   Rob Herring <robh@...nel.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     John Crispin <john@...ozen.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Frank Rowand <frowand.list@...il.com>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Frank Rowand <frank.rowand@...y.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v3] of/fdt: Rework early_init_dt_scan_memory() to call directly

On Wed, Dec 15, 2021 at 4:13 AM Michael Ellerman <mpe@...erman.id.au> wrote:
>
> Rob Herring <robh@...nel.org> writes:
> > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > index 5e216555fe4f..97d7607625ec 100644
> > --- a/drivers/of/fdt.c
> > +++ b/drivers/of/fdt.c
> > @@ -1078,49 +1078,50 @@ u64 __init dt_mem_next_cell(int s, const __be32 **cellp)
> >  /*
> >   * early_init_dt_scan_memory - Look for and parse memory nodes
> >   */
> > -int __init early_init_dt_scan_memory(unsigned long node, const char *uname,
> > -                                  int depth, void *data)
> > +int __init early_init_dt_scan_memory(void)
> >  {
> > -     const char *type = of_get_flat_dt_prop(node, "device_type", NULL);
> > -     const __be32 *reg, *endp;
> > -     int l;
> > -     bool hotpluggable;
> > -
> > -     /* We are scanning "memory" nodes only */
> > -     if (type == NULL || strcmp(type, "memory") != 0)
> > -             return 0;
> > +     int node;
> > +     const void *fdt = initial_boot_params;
> >
> > -     reg = of_get_flat_dt_prop(node, "linux,usable-memory", &l);
> > -     if (reg == NULL)
> > -             reg = of_get_flat_dt_prop(node, "reg", &l);
> > -     if (reg == NULL)
> > -             return 0;
> > +     for (node = fdt_node_offset_by_prop_value(fdt, -1, "device_type", "memory", 6);
> > +          node != -FDT_ERR_NOTFOUND;
> > +          node = fdt_node_offset_by_prop_value(fdt, node, "device_type", "memory", 6)) {
>
> The 6 there doesn't work on my machines.

Crap! I meant to keep the original version and just fix the return.

>
> It needs to match the trailing NULL, so 7 or sizeof("memory") works.

That's what I get for trying to look thru libfdt to see what it wants.
Seems to be strlen() on property names and strlen()+1 on values.

Rob