On Wed, Jun 14, 2017 at 3:56 PM, Joe Perches <joe@xxxxxxxxxxx> wrote: > 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' Okay, but it was good enough for the 2-3 versions Pantelis did before... >> 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. So %pOFfullname? We've beat this one to death IMO. > >> 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. 2-6 I'd say is typical. The FDT unflattening code limits things to 64 (which is probably way more than needed). I could re-write it to be non-recursive, but then I'll just have the max sized array of pointers on the stack. > >> + >> + if (buf < end) >> + len = end - buf; >> + else >> + len = 0; >> + ret = snprintf(buf, len, "/%s", kbasename(np->full_name)); I can replace this one too with a strcat and save some stack space. >> + 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. widen_string is called at the end of device_node_string. >> +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? Okay. > >> + 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. Okay. > It's probably better to avoid more recursion stack depth use > and just use *buf++ as appropriate. You can't use *buf++ as this code must work and increment buf even when buf is NULL. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html