linux-kernel - Re: [PATCH 5/5] lib/vsprintf: Add %pfw conversion specifier for printing fwnode names

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Message-ID: <20190322172114.GY9224@smile.fi.intel.com>
Date:   Fri, 22 Mar 2019 19:21:14 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     Petr Mladek <pmladek@...e.com>, linux-kernel@...r.kernel.org,
        rafael@...nel.org, linux-acpi@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 5/5] lib/vsprintf: Add %pfw conversion specifier for
 printing fwnode names

On Fri, Mar 22, 2019 at 05:29:30PM +0200, Sakari Ailus wrote:
> Add support for %pfw conversion specifier (with "f" and "P" modifiers) to
> support printing full path of the node, including its name ("f") and only
> the node's name ("P") in the printk family of functions. The two flags
> have equivalent functionality to existing %pOF with the same two modifiers
> ("f" and "P") on OF based systems. The ability to do the same on ACPI
> based systems is added by this patch.

Do we encourage people to use it instead of %pOF cases where it is suitable?

> On ACPI based systems the resulting strings look like
> 
> 	\_SB.PCI0.CIO2.port@...ndpoint@0
> 
> where the nodes are separated by a dot (".") and the first three are
> ACPI device nodes and the latter two ACPI data nodes.

Do we support swnode here?

> +static noinline_for_stack
> +char *fwnode_string(char *buf, char *end, struct fwnode_handle *fwnode,
> +		    struct printf_spec spec, const char *fmt)
> +{
> +	const char * const modifiers = "fP";
> +	struct printf_spec str_spec = spec;
> +	char *buf_start = buf;
> +	bool pass;
> +
> +	str_spec.field_width = -1;
> +

> +	if ((unsigned long)fwnode < PAGE_SIZE)
> +		return string(buf, end, "(null)", spec);

Just put there a NULL pointer, we would not like to maintain duplicated strings
over the kernel.

I remember Petr has a patch series related to address space check, though I
don't remember the status of affairs.

> +
> +	/* simple case without anything any more format specifiers */
> +	fmt++;
> +	if (fmt[0] == '\0' || strcspn(fmt, modifiers) > 0)
> +		fmt = "f";
> +
> +	for (pass = false; strspn(fmt, modifiers); fmt++, pass = true) {

I don't see test cases.

What would we get out of %pfwfffPPPfff?

Hint: I'm expecting above to be equivalent to %pfwf

> +		if (pass) {
> +			if (buf < end)
> +				*buf = ':';
> +			buf++;
> +		}
> +
> +		switch (*fmt) {
> +		case 'f':	/* full_name */
> +			buf = fwnode_gen_full_name(fwnode, buf, end);
> +			break;
> +		case 'P':	/* name */
> +			buf = string(buf, end, fwnode_get_name(fwnode),
> +				     str_spec);
> +			break;
> +		default:
> +			break;
> +		}
> +	}
> +
> +	return widen_string(buf, buf - buf_start, end, spec);
> +}

-- 
With Best Regards,
Andy Shevchenko