Re: [PATCH v7 44/50] drivers/of: Split unflatten_dt_node()

Gavin Shan
2015-11-04T23:06:46Z

On Wed, Nov 04, 2015 at 12:43:08PM -0600, Rob Herring wrote:
>On Wed, Nov 4, 2015 at 7:12 AM, Gavin Shan <gwshan@linux.vnet.ibm.com> wrote:
>> The function unflatten_dt_node() is called recursively to unflatten
>> device nodes and properties in the FDT blob. It looks complicated
>> and hard to be understood.
>>
>> This splits the function into 3 functions: populate_properties(),
>> populate_node() and unflatten_dt_node(). populate_properties(),
>> which is called by populate_node(), creates properties for the
>> indicated device node. The later one creates the device nodes
>> from FDT blob. populate_node() gets the offset in FDT blob for
>> next device nodes and then calls populate_node(). No logical
>> changes introduced.
>>
>> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
>> ---
>> drivers/of/fdt.c | 275 ++++++++++++++++++++++++++++++++-----------------------
>> 1 file changed, 160 insertions(+), 115 deletions(-)
>>
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index 6e82bc42..173b036 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -160,39 +160,127 @@ static void *unflatten_dt_alloc(void **mem, unsigned long size,
>> return res;
>> }
>>
>> -/**
>> - * unflatten_dt_node - Alloc and populate a device_node from the flat tree
>> - * @blob: The parent device tree blob
>> - * @mem: Memory chunk to use for allocating device nodes and properties
>> - * @poffset: pointer to node in flat tree
>> - * @dad: Parent struct device_node
>> - * @nodepp: The device_node tree created by the call
>> - * @fpsize: Size of the node path up at the current depth.
>> - * @dryrun: If true, do not allocate device nodes but still calculate needed
>> - * memory size
>> - */
>> -static void * unflatten_dt_node(const void *blob,
>> - void *mem,
>> - int *poffset,
>> - struct device_node *dad,
>> - struct device_node **nodepp,
>> - unsigned long fpsize,
>> +static void populate_properties(const void *blob,
>> + int offset,
>> + void **mem,
>> + struct device_node *np,
>> + const char *nodename,
>> bool dryrun)
>
>I'd like to make dryrun implicit. It is basically a function of NULL
>or near NULL pointers.
>

[1] The condition would be something like below:

if ((unsigned long)(*mem) < limit)
dryrun = true;
else
dryrun = false;

The question here is how to choose a sane @limit in practice. In !dryrun case,
the memory is allocated from memblock at system booting time, or slab when system
is up. memblock could assign memory in bottom-up fasion.

When @limit is too small, the condition wouldn't be comprehensive in !dryrun
case. When @limit is too large, the !dryrun cases can be regarded as dryrun case.

>> {
>> - const __be32 *p;
>> + struct property *pp, **pprev = NULL;
>> + int cur;
>> + bool has_name = false;
>> +
>> + pprev = &np->properties;
>> + cur = fdt_first_property_offset(blob, offset);
>> + while (cur >= 0) {
>
>This could be better written as a for loop to avoid the gotos:
>
>for (cur = fdt_first_property_offset(blob, offset); cur >=0; cur =
>fdt_next_property_offset(blob, cur))
>

Thanks, the changes will be included in next revision.

>> + const __be32 *val;
>> + const char *pname;
>> + u32 sz;
>> +
>> + val = fdt_getprop_by_offset(blob, cur, &pname, &sz);
>> + if (!val) {
>> + pr_warn("%s: Cannot locate property at 0x%x\n",
>> + __func__, cur);
>> + goto next;
>> + }
>> +
>> + if (!pname) {
>> + pr_warn("%s: Cannot find property name at 0x%x\n",
>> + __func__, cur);
>> + goto next;
>> + } else if (!strcmp(pname, "name")) {
>> + has_name = true;
>> + }
>> +
>> + pp = unflatten_dt_alloc(mem, sizeof(struct property),
>> + __alignof__(struct property));
>> + if (!dryrun) {
>
>Then:
>
>if (dryrun)
> continue;
>
>to save some indentation and vertical code.
>

Good idea, it will be included in next revision.

>> + /* We accept flattened tree phandles either in
>> + * ePAPR-style "phandle" properties, or the
>> + * legacy "linux,phandle" properties. If both
>> + * appear and have different values, things
>> + * will get weird. Don't do that.
>> + */
>> + if (!strcmp(pname, "phandle") ||
>> + !strcmp(pname, "linux,phandle")) {
>> + if (!np->phandle)
>> + np->phandle = be32_to_cpup(val);
>> + }
>> +
>> + /* And we process the "ibm,phandle" property
>> + * used in pSeries dynamic device tree
>> + * stuff
>> + */
>> + if (!strcmp(pname, "ibm,phandle"))
>> + np->phandle = be32_to_cpup(val);
>> +
>> + pp->name = (char *)pname;
>> + pp->length = sz;
>> + pp->value = (__be32 *)val;
>> + *pprev = pp;
>> + pprev = &pp->next;
>> + }
>> +next:
>> + cur = fdt_next_property_offset(blob, cur);
>> + }
>> +
>> + /* With version 0x10 we may not have the name property,
>> + * recreate it here from the unit name if absent
>> + */
>> + if (!has_name) {
>> + const char *p = nodename, *ps = p, *pa = NULL;
>> + int len;
>> +
>> + while (*p) {
>> + if ((*p) == '@')
>> + pa = p;
>> + else if ((*p) == '/')
>> + ps = p + 1;
>> + p++;
>> + }
>> +
>> + if (pa < ps)
>> + pa = p;
>> + len = (pa - ps) + 1;
>> + pp = unflatten_dt_alloc(mem, sizeof(struct property) + len,
>> + __alignof__(struct property));
>> + if (!dryrun) {
>> + pp->name = "name";
>> + pp->length = len;
>> + pp->value = pp + 1;
>> + *pprev = pp;
>> + pprev = &pp->next;
>> + memcpy(pp->value, ps, len - 1);
>> + ((char *)pp->value)[len - 1] = 0;
>> + pr_debug("fixed up name for %s -> %s\n",
>> + nodename, (char *)pp->value);
>> + }
>> + }
>> +
>> + if (!dryrun)
>> + *pprev = NULL;
>> +}
>> +
>> +static unsigned long populate_node(const void *blob,
>> + int offset,
>> + void **mem,
>> + struct device_node *dad,
>> + unsigned long fpsize,
>> + struct device_node **pnp,
>> + bool dryrun)
>
>I think dryrun could be implied here too.
>

I don't think so. Please refer to the explanation at [1].

>> +{
>> struct device_node *np;
>> - struct property *pp, **prev_pp = NULL;
>> const char *pathp;
>> unsigned int l, allocl;
>> - static int depth = 0;
>> - int old_depth;
>> - int offset;
>> - int has_name = 0;
>> - int new_format = 0;
>> + bool new_format = false;
>> + char *fname;
>>
>> - pathp = fdt_get_name(blob, *poffset, &l);
>> - if (!pathp)
>> - return mem;
>> + pathp = fdt_get_name(blob, offset, &l);
>> + if (!pathp) {
>> + *pnp = NULL;
>
>Can't pnp be NULL?
>

It can't be NULL in both dryrun and !dryrun cases.

>> + return 0;
>> + }
>>
>> allocl = ++l;
>>
>> @@ -202,7 +290,7 @@ static void * unflatten_dt_node(const void *blob,
>> * not '/'.
>> */
>> if ((*pathp) != '/') {
>> - new_format = 1;
>> + new_format = true;
>> if (fpsize == 0) {
>> /* root node: special case. fpsize accounts for path
>> * plus terminating zero. root node only has '/', so
>> @@ -222,112 +310,38 @@ static void * unflatten_dt_node(const void *blob,
>> }
>> }
>>
>> - np = unflatten_dt_alloc(&mem, sizeof(struct device_node) + allocl,
>> + np = unflatten_dt_alloc(mem, sizeof(struct device_node) + allocl,
>> __alignof__(struct device_node));
>> if (!dryrun) {
>> - char *fn;
>> of_node_init(np);
>> - np->full_name = fn = ((char *)np) + sizeof(*np);
>> + np->full_name = fname = ((char *)np) + sizeof(*np);
>
>If you kept "fn" that would cut down the diff and make it a bit easier
>to review.
>

Agree, I'll drop the rename in next revision. I perhaps have separate
patch to do the renaming after this patch. In that way, unrelated code
changes will be avoided in this one.

>> if (new_format) {
>> - /* rebuild full path for new format */
>> + /* Rebuild full path for new format */
>> if (dad && dad->parent) {
>> - strcpy(fn, dad->full_name);
>> + strcpy(fname, dad->full_name);
>> #ifdef DEBUG
>> - if ((strlen(fn) + l + 1) != allocl) {
>> + if ((strlen(fname) + l + 1) != allocl) {
>> pr_debug("%s: p: %d, l: %d, a: %d\n",
>> - pathp, (int)strlen(fn),
>> - l, allocl);
>> + pathp, (int)strlen(fn),
>
>This won't compile if enabled (should be fname).
>

Indeed, I even didn't try to compile this piece of debugging code. Will change
accordingly in next revision.

>> + l, allocl);
>> }
>> #endif
>> - fn += strlen(fn);
>> + fname += strlen(fname);
>> }
>> - *(fn++) = '/';
>> + *(fname++) = '/';
>> }
>> - memcpy(fn, pathp, l);
>> + memcpy(fname, pathp, l);
>>
>> - prev_pp = &np->properties;
>> - if (dad != NULL) {
>> + if (dad) {
>> np->parent = dad;
>> np->sibling = dad->child;
>> dad->child = np;
>> }
>> }
>> - /* process properties */
>> - for (offset = fdt_first_property_offset(blob, *poffset);
>> - (offset >= 0);
>> - (offset = fdt_next_property_offset(blob, offset))) {
>> - const char *pname;
>> - u32 sz;
>>
>> - if (!(p = fdt_getprop_by_offset(blob, offset, &pname, &sz))) {
>> - offset = -FDT_ERR_INTERNAL;
>> - break;
>> - }
>> -
>> - if (pname == NULL) {
>> - pr_info("Can't find property name in list !\n");
>> - break;
>> - }
>> - if (strcmp(pname, "name") == 0)
>> - has_name = 1;
>> - pp = unflatten_dt_alloc(&mem, sizeof(struct property),
>> - __alignof__(struct property));
>> - if (!dryrun) {
>> - /* We accept flattened tree phandles either in
>> - * ePAPR-style "phandle" properties, or the
>> - * legacy "linux,phandle" properties. If both
>> - * appear and have different values, things
>> - * will get weird. Don't do that. */
>> - if ((strcmp(pname, "phandle") == 0) ||
>> - (strcmp(pname, "linux,phandle") == 0)) {
>> - if (np->phandle == 0)
>> - np->phandle = be32_to_cpup(p);
>> - }
>> - /* And we process the "ibm,phandle" property
>> - * used in pSeries dynamic device tree
>> - * stuff */
>> - if (strcmp(pname, "ibm,phandle") == 0)
>> - np->phandle = be32_to_cpup(p);
>> - pp->name = (char *)pname;
>> - pp->length = sz;
>> - pp->value = (__be32 *)p;
>> - *prev_pp = pp;
>> - prev_pp = &pp->next;
>> - }
>> - }
>> - /* with version 0x10 we may not have the name property, recreate
>> - * it here from the unit name if absent
>> - */
>> - if (!has_name) {
>> - const char *p1 = pathp, *ps = pathp, *pa = NULL;
>> - int sz;
>> -
>> - while (*p1) {
>> - if ((*p1) == '@')
>> - pa = p1;
>> - if ((*p1) == '/')
>> - ps = p1 + 1;
>> - p1++;
>> - }
>> - if (pa < ps)
>> - pa = p1;
>> - sz = (pa - ps) + 1;
>> - pp = unflatten_dt_alloc(&mem, sizeof(struct property) + sz,
>> - __alignof__(struct property));
>> - if (!dryrun) {
>> - pp->name = "name";
>> - pp->length = sz;
>> - pp->value = pp + 1;
>> - *prev_pp = pp;
>> - prev_pp = &pp->next;
>> - memcpy(pp->value, ps, sz - 1);
>> - ((char *)pp->value)[sz - 1] = 0;
>> - pr_debug("fixed up name for %s -> %s\n", pathp,
>> - (char *)pp->value);
>> - }
>> - }
>> + /* Populate the properties */
>
>Kind of a useless comment.
>

Agree, will drop in next revision.

>> + populate_properties(blob, offset, mem, np, pathp, dryrun);
>> if (!dryrun) {
>> - *prev_pp = NULL;
>> np->name = of_get_property(np, "name", NULL);
>> np->type = of_get_property(np, "device_type", NULL);
>>
>> @@ -337,6 +351,37 @@ static void * unflatten_dt_node(const void *blob,
>> np->type = "<NULL>";
>> }
>>
>> + *pnp = np;
>> + return fpsize;
>> +}
>> +
>> +/**
>> + * unflatten_dt_node - Alloc and populate a device_node from the flat tree
>> + * @blob: The parent device tree blob
>> + * @mem: Memory chunk to use for allocating device nodes and properties
>> + * @poffset: pointer to node in flat tree
>> + * @dad: Parent struct device_node
>> + * @nodepp: The device_node tree created by the call
>> + * @fpsize: Size of the node path up at the current depth.
>> + * @dryrun: If true, do not allocate device nodes but still calculate needed
>> + * memory size
>> + */
>> +static void *unflatten_dt_node(const void *blob,
>> + void *mem,
>> + int *poffset,
>> + struct device_node *dad,
>> + struct device_node **nodepp,
>> + unsigned long fpsize,
>> + bool dryrun)
>> +{
>> + struct device_node *np;
>> + static int depth;
>> + int old_depth;
>> +
>> + fpsize = populate_node(blob, *poffset, &mem, dad, fpsize, &np, dryrun);
>
>Doesn't this give a warning assigning a ptr to long?
>
>Looks like np can be moved internal to populate_node.
>

@fpsize and the return value of populate_node() are "unsigned long".

Nope, @np will be used in next patch in this function, which tracks the
device node unflattened in last level of depth.

>
>> + if (!fpsize)
>> + return mem;
>> +
>> old_depth = depth;
>> *poffset = fdt_next_node(blob, *poffset, &depth);
>> if (depth < 0)

Thanks,
Gavin