On Wed, Nov 13, 2013 at 4:51 PM, Rob Herring <robherring2@xxxxxxxxx> wrote:
> On Tue, Nov 12, 2013 at 1:42 PM, Geert Uytterhoeven
> <geert@xxxxxxxxxxxxxx> wrote:
>> The different architectures used their own (and different) declarations:
>>
>> extern struct boot_param_header __dtb_start;
>> extern u32 __dtb_start[];
>> extern char __dtb_start[];
>>
>> Consolidate them using the first variant in <linux/of_fdt.h>.
>> This requires adding a few "address of" operators on architectures where
>> __dtb_start was an array before.
>>
>> Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
>> Cc: Vineet Gupta <vgupta@xxxxxxxxxxxx>
>> Cc: James Hogan <james.hogan@xxxxxxxxxx>
>> Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
>> Cc: Jonas Bonn <jonas@xxxxxxxxxxxx>
>> CC: Chris Zankel <chris@xxxxxxxxxx>
>> Cc: Rob Herring <rob.herring@xxxxxxxxxxx>
>> Cc: devicetree@xxxxxxxxxxxxxxx
>> ---
>> arch/arc/include/asm/sections.h | 1 -
>> arch/arc/kernel/setup.c | 2 +-
>> arch/metag/kernel/setup.c | 6 +-----
>> arch/mips/include/asm/mips-boards/generic.h | 4 ----
>> arch/mips/lantiq/prom.h | 2 --
>> arch/mips/netlogic/xlp/dt.c | 4 ++--
>> arch/mips/ralink/of.c | 2 --
>> arch/openrisc/kernel/setup.c | 2 +-
>> arch/openrisc/kernel/vmlinux.h | 2 --
>> arch/xtensa/kernel/setup.c | 3 +--
>> include/linux/of_fdt.h | 3 +++
>> 11 files changed, 9 insertions(+), 22 deletions(-)
>
> This is great, but I would like to see this taken one step further and
> move the selection logic into the core code. We can try to use the
> built-in dtb if early_init_dt_scan is passed a NULL or invalid dtb. This
> should work for most arches I think and still allows an arch to do a
> different selection algorithm if desired.
Yes, that makes sense.
> Are the DT related patches dependent on the rest of the series?
Not really. There may be small rejects if you apply it out-of-order,
but nothing serious.
> Something like this is what I have in mind:
>
> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> index 5c47910..723f854d 100644
> --- a/drivers/of/fdt.c
> +++ b/drivers/of/fdt.c
> @@ -869,14 +869,16 @@ void * __init __weak
> early_init_dt_alloc_memory_arch(u64 size, u64 align)
>
> bool __init early_init_dt_scan(void *params)
> {
> - if (!params)
> - return false;
> -
> /* Setup flat device-tree pointer */
> initial_boot_params = params;
>
> + if (!initial_boot_params ||
> + (be32_to_cpu(initial_boot_params->magic) != OF_DT_HEADER))
> + initial_boot_params = &__dtb_start;
> +
> /* check device tree validity */
> - if (be32_to_cpu(initial_boot_params->magic) != OF_DT_HEADER) {
> + if (!initial_boot_params ||
initial_boot_params cannot be NULL here, so no need to check.
> + (be32_to_cpu(initial_boot_params->magic) != OF_DT_HEADER)) {
However, if __dtb_end == __dtb_start, you may be reading random
data here from the next section. The OF_DT_HEADER check should cover
this, but better safe than sorry?
> initial_boot_params = NULL;
> return false;
> }
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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