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

Rob Herring
2015-11-04T18:43:28Z

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.

> {
> - 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))

> + 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.

> + /* 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.

> +{
> 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?

> + 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.

> 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).

> + 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.

> + 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.

> + if (!fpsize)
> + return mem;
> +
> old_depth = depth;
> *poffset = fdt_next_node(blob, *poffset, &depth);
> if (depth < 0)
> --
> 2.1.0
>