On Wed, 2017-06-14 at 15:30 -0500, Rob Herring wrote:
> From: Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx>
I think the commit subject is wrong.
It adds an "of" specific bit to vsprintf.c.
The subject should be
'vsprintf: Add %p extension "%pO" for device tree'
> 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.
>
> For instance typical use is:
> pr_info("Frobbing node %s\n", node->full_name);
>
> Which can be written now as:
> pr_info("Frobbing node %pOF\n", node);
Somehow I think this example is poor as node->full_name
is a pretty obvious to read use. %pOF requires you to
look up or know what the output is going to be.
> More fine-grained control of formatting includes printing the name,
> flag, path-spec name, reference count and others, explained in the
> documentation entry.
>
> Originally written by Pantelis, but pretty much rewrote the core
> function using existing string/number functions. The 2 passes were
> unnecessary and have been removed. Also, updated the checkpatch.pl
> check.
Some comments about the code.
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> []
> @@ -1470,6 +1471,123 @@ char *flags_string(char *buf, char *end, void *flags_ptr, const char *fmt)
> return format_flags(buf, end, flags, names);
> }
>
> +static noinline_for_stack
> +char *device_node_gen_full_name(const struct device_node *np, char *buf, char *end)
> +{
> + int len, ret;
> +
> + if (!np || !np->parent)
> + return buf;
> +
> + buf = device_node_gen_full_name(np->parent, buf, end);
This is recursive. How many levels of parents could there be?
Perhaps there should be a recursion limit.
> +
> + if (buf < end)
> + len = end - buf;
> + else
> + len = 0;
> + ret = snprintf(buf, len, "/%s", kbasename(np->full_name));
> + if (ret <= 0)
> + return buf;
> + else if (len == 0 || ret < len)
> + return buf + ret;
> + return buf + len;
> +}
Does this work with %p<len>OF for a right justified or padded
length string? Perhaps widen_string should be added.
> +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") + 1];
> + const char *fmtp, *p;
> + int ret;
> + char *buf_start = buf;
> + struct property *prop;
> + bool has_mult, pass;
> + const struct printf_spec num_spec = {
> + .flags = SMALL,
> + .field_width = -1,
> + .precision = -1,
> + .base = 10,
> + };
> +
> + struct printf_spec str_spec = spec;
> + str_spec.field_width = -1;
> +
> + if (!IS_ENABLED(CONFIG_OF))
> + return string(buf, end, "(!OF)", spec);
> +
> + if ((unsigned long)dn < PAGE_SIZE)
> + return string(buf, end, "(null)", spec);
> +
> + /* simple case without anything any more format specifiers */
> + if (fmt[1] == '\0' || strcspn(fmt + 1,"fnpPFcCr") > 0)
> + fmt = "Ff";
> +
> + for (fmtp = fmt + 1, pass = false; strspn(fmtp,"fnpPFcCr"); fmtp++, pass = true) {
why not
while (isalpha(*++fmt))
like ip6 or isalnum like FORMAT_TYPE_PTR uses?
> + if (pass && (*fmtp != 'f')) {
> + if (buf < end)
> + *buf = '|';
> + buf++;
> + }
> +
> + switch (*fmtp) {
> + case 'f': /* full_name */
> + if (pass) {
> + if (buf < end)
> + *buf = ':';
> + buf++;
> + }
> + buf = device_node_gen_full_name(dn, buf, end);
> + break;
> + case 'n': /* name */
> + buf = string(buf, end, dn->name, str_spec);
> + break;
> + case 'p': /* phandle */
> + buf = number(buf, end, (unsigned int)dn->phandle, num_spec);
> + break;
> + case 'P': /* path-spec */
> + buf = string(buf, end, kbasename(of_node_full_name(dn)), str_spec);
> + break;
> + case 'F': /* flags */
> + snprintf(tbuf, sizeof(tbuf), "%c%c%c%c",
> + 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' : '-');
I'd try to avoid all uses of snprintf as it's effectively
another fairly
large stack frame.
It's probably better to avoid more recursion stack depth use
and just use *buf++ as appropriate.
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