Re: [PATCH] commands: add new of_fixup command to list and disable DT fixups

[Sascha Hauer <sha@pengutronix.de>]

On Fri, Feb 17, 2023 at 09:31:48PM +0100, Ahmad Fatoum wrote:
> For debugging, it can be useful to disable a fixup to rule out it causing
> issues. For platforms supporting kallsyms, we can readily allow enabling
> and disabling fixups by name, so let's add a command that does just that.
> 
> Suggested-by: Daniel Brát <danek.brat@gmail.com>
> Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
> ---
>  commands/Kconfig    | 15 ++++++++
>  commands/Makefile   |  1 +
>  commands/of_fixup.c | 86 +++++++++++++++++++++++++++++++++++++++++++++
>  common/kallsyms.c   |  8 ++---
>  common/oftree.c     | 17 +++++----
>  drivers/of/Kconfig  |  6 ++++
>  include/kallsyms.h  |  4 +++
>  include/of.h        | 10 ++++++
>  8 files changed, 137 insertions(+), 10 deletions(-)
>  create mode 100644 commands/of_fixup.c
> 
> +static int do_of_fixup(int argc, char *argv[])
> +{
> +	struct of_fixup *of_fixup;
> +	int opt, enable = -1;
> +
> +	while ((opt = getopt(argc, argv, "ed")) > 0) {
> +		switch (opt) {
> +		case 'e':
> +			enable = 1;
> +			break;
> +		case 'd':
> +			enable = 0;
> +			break;
> +		default:
> +			return COMMAND_ERROR_USAGE;
> +		}
> +	}
> +
> +	argv += optind;
> +	argc -= optind;
> +
> +	if ((enable < 0 && argc > 0) || (enable >= 0 && argc == 0))
> +		return COMMAND_ERROR_USAGE;
> +
> +	list_for_each_entry(of_fixup, &of_fixup_list, list) {
> +		int i;
> +		ulong addr = (ulong)of_fixup->fixup;
> +		char sym[KSYM_SYMBOL_LEN];
> +		const char *name;
> +
> +		name = kallsyms_lookup(addr, NULL, NULL, NULL, sym);
> +		if (!name) {
> +			sprintf(sym, "<0x%lx>", addr);
> +			name = sym;
> +		}

Does this fallback make sense? kallsyms_lookup() should always return a
name, otherwise something is really wrong.

> +
> +		if (enable == -1) {
> +			printf("%s(0x%p)%s\n", name, of_fixup->context,
> +			       of_fixup->disabled ? " [DISABELD]" : "");

s/DISABELD/DISABLED/

We can have the same fixup function with different contexts, that's why
you print the context pointer here. Shouldn't we then have a way to
disable a specific fixup, like "of_fixup -d mtd_partition_fixup(0x2fed7a00)"?

Sascha

> +config OF_FIXUP_TOGGLE
> +	bool
> +	help
> +	  This is selected when some device tree fixups may be selectively
> +	  disabled.

Why does this have an extra config option? It doesn't look like it's
saving a lot of binary space.

Sascha

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