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Date: Tue, 20 Jan 2015 08:47:49 -0600
From: Rob Herring <robherring2@...il.com>
To: Pantelis Antoniou <pantelis.antoniou@...sulko.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Grant Likely <grant.likely@...retlab.ca>,
Randy Dunlap <rdunlap@...radead.org>,
"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Pantelis Antoniou <panto@...oniou-consulting.com>
Subject: Re: [PATCH] of: Custom printk format specifier for device node
On Tue, Jan 20, 2015 at 8:34 AM, Pantelis Antoniou
<pantelis.antoniou@...sulko.com> wrote:
> 90% of the usage of device node's full_name is printing it out
> in a kernel message. Preparing for the eventual delayed allocation
> introduce a custom printk format specifier that is both more
> compact and more pleasant to the eye.
What a great idea. ;)
> For instance typical use is:
> pr_info("Frobbing node %s\n", node->full_name);
>
> Which can be written now as:
> pr_info("Frobbing node %pO\n", node);
>
> A verbose format specifier (1-2) can be used to print extra
> information about the node like its phandle and node flags.
>
> Signed-off-by: Pantelis Antoniou <pantelis.antoniou@...sulko.com>
> ---
> Documentation/printk-formats.txt | 18 +++++++++++
> lib/vsprintf.c | 67 ++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 85 insertions(+)
>
> diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
> index 5a615c1..6ad199f 100644
> --- a/Documentation/printk-formats.txt
> +++ b/Documentation/printk-formats.txt
> @@ -231,6 +231,24 @@ struct va_format:
> Do not use this feature without some mechanism to verify the
> correctness of the format string and va_list arguments.
>
> +Device tree nodes:
> +
> + %pO{,1,2}
'O' is not very obvious, but I imagine we are somewhat limted in our
choice here?
> +
> + For printing device tree nodes. The (optional) number is the verbosity
> + level.
> +
> + Examples:
> +
> + %pO /foo/bar@0 - Node full name
> + %pO0 /foo/bar@0 - Same as above
> + %pO1 /foo/bar@0[10] - Node full name + phandle
> + %pO2 /foo/bar@0[10:DdPB] - Node full name + phandle + node flags
> + D - dynamic
> + d - detached
> + P - Populated
> + B - Populated bus
We should think about what else we want to print for a node. Perhaps
'On' for name, 'Oc' for compatible, etc.
> +
> u64 SHOULD be printed with %llu/%llx:
>
> printk("%llu", u64_var);
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index ec337f6..72896cc 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -29,6 +29,7 @@
> #include <linux/dcache.h>
> #include <linux/cred.h>
> #include <net/addrconf.h>
> +#include <linux/of.h>
>
> #include <asm/page.h> /* for PAGE_SIZE */
> #include <asm/sections.h> /* for dereference_function_descriptor() */
> @@ -1240,6 +1241,68 @@ char *address_val(char *buf, char *end, const void *addr,
> return number(buf, end, num, spec);
> }
>
> +#if IS_ENABLED(CONFIG_OF)
You can move this into the function:
if (!IS_ENABLED(CONFIG_OF)
return NULL;
Looks like you'll need the patch for empty of_node_check_flag as well.
> +static noinline_for_stack
> +char *device_node_string(char *buf, char *end, struct device_node *dn,
> + struct printf_spec spec, const char *fmt)
> +{
> + char tbuf[sizeof("[xxxxxxxxxx:xxxx]") + 1];
> + const char *full_name;
> + int verbosity, len, flen, i;
> +
> + if ((unsigned long)dn < PAGE_SIZE)
> + return string(buf, end, "(null)", spec);
> +
> + full_name = of_node_full_name(dn);
> + verbosity = 0;
> + if (fmt[1] >= '0' && fmt[1] <= '2')
> + verbosity = fmt[1] - '0';
> +
> + /* fast and simple case */
> + switch (verbosity) {
> + default:
> + case 0:
> + tbuf[0] = '\0';
> + break;
> + case 1:
> + snprintf(tbuf, sizeof(tbuf), "[%u]",
> + (u32)dn->phandle);
> + break;
> + case 2:
> + snprintf(tbuf, sizeof(tbuf), "[%u:%c%c%c%c]",
> + (u32)dn->phandle,
> + of_node_check_flag(dn, OF_DYNAMIC) ? 'D' : '-',
> + of_node_check_flag(dn, OF_DETACHED) ? 'd' : '-',
> + of_node_check_flag(dn, OF_POPULATED) ? 'P' : '-',
> + of_node_check_flag(dn, OF_POPULATED_BUS) ? 'B' : '-');
> + break;
> + }
> + flen = strlen(full_name);
> + len = flen + strlen(tbuf);
> + if (spec.precision > 0 && len > spec.precision)
> + len = spec.precision;
> +
> + if (!(spec.flags & LEFT)) {
> + while (len < spec.field_width--) {
> + if (buf < end)
> + *buf = ' ';
> + ++buf;
> + }
> + }
> + for (i = 0; i < len; ++i) {
> + if (buf < end)
> + *buf = i < flen ? full_name[i] : tbuf[i - flen];
> + ++buf;
> + }
> + while (len < spec.field_width--) {
> + if (buf < end)
> + *buf = ' ';
> + ++buf;
> + }
> + return buf;
> +}
> +#endif
> +
> int kptr_restrict __read_mostly;
>
> /*
> @@ -1459,6 +1522,10 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
> return dentry_name(buf, end,
> ((const struct file *)ptr)->f_path.dentry,
> spec, fmt);
> +#if IS_ENABLED(CONFIG_OF)
With the above, then this ifdef should not be needed.
> + case 'O':
> + return device_node_string(buf, end, ptr, spec, fmt);
> +#endif
> }
> spec.flags |= SMALL;
> if (spec.field_width == -1) {
> --
> 1.7.12
>
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