Re: [PATCH v4 1/4] of: remove *phandle properties from expanded device tree

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On 05/15/17 15:23, Rob Herring wrote:
> On Mon, May 1, 2017 at 9:46 PM,  <frowand.list@xxxxxxxxx> wrote:
>> From: Frank Rowand <frank.rowand@xxxxxxxx>
>>
>> Remove "phandle", "linux,phandle", and "ibm,phandle" properties from
>> the internal device tree.  The phandle will still be in the struct
>> device_node phandle field.
>>
>> This is to resolve the issue found by Stephen Boyd [1] when he changed
>> the type of struct property.value from void * to const void *.  As
>> a result of the type change, the overlay code had compile errors
>> where the resolver updates phandle values.
>>
>>   [1] http://lkml.iu.edu/hypermail/linux/kernel/1702.1/04160.html
>>
>> - Add sysfs infrastructure to report np->phandle, as if it was a property.
>> - Do not create "phandle" "ibm,phandle", and "linux,phandle" properties
>>   in the expanded device tree.
>> - Remove phandle properties in of_attach_node(), for nodes dynamically
>>   attached to the live tree.  Add the phandle sysfs entry for these nodes.
>> - When creating an overlay changeset, duplicate the node phandle in
>>   __of_node_dup().
>> - Remove no longer needed checks to exclude "phandle" and "linux,phandle"
>>   properties in several locations.
>> - A side effect of these changes is that the obsolete "linux,phandle" and
>>   "ibm,phandle" properties will no longer appear in /proc/device-tree (they
>>   will appear as "phandle").
>>
>> Signed-off-by: Frank Rowand <frank.rowand@xxxxxxxx>
>> ---
>>  drivers/of/base.c       | 48 ++++++++++++++++++++++++++++++++++++++++---
>>  drivers/of/dynamic.c    | 54 +++++++++++++++++++++++++++++++++++++------------
>>  drivers/of/fdt.c        | 40 +++++++++++++++++++++---------------
>>  drivers/of/of_private.h |  1 +
>>  drivers/of/overlay.c    |  4 +---
>>  drivers/of/resolver.c   | 23 +--------------------
>>  include/linux/of.h      |  1 +
>>  7 files changed, 114 insertions(+), 57 deletions(-)
>>
>> diff --git a/drivers/of/base.c b/drivers/of/base.c
>> index d7c4629a3a2d..8a0cf9003cf8 100644
>> --- a/drivers/of/base.c
>> +++ b/drivers/of/base.c
>> @@ -116,6 +116,19 @@ static ssize_t of_node_property_read(struct file *filp, struct kobject *kobj,
>>         return memory_read_from_buffer(buf, count, &offset, pp->value, pp->length);
>>  }
>>
>> +static ssize_t of_node_phandle_read(struct file *filp, struct kobject *kobj,
>> +                               struct bin_attribute *bin_attr, char *buf,
>> +                               loff_t offset, size_t count)
>> +{
>> +       phandle phandle;
>> +       struct device_node *np;
>> +
>> +       np = container_of(bin_attr, struct device_node, attr_phandle);
>> +       phandle = cpu_to_be32(np->phandle);
>> +       return memory_read_from_buffer(buf, count, &offset, &phandle,
>> +                                      sizeof(phandle));
>> +}
>> +
>>  /* always return newly allocated name, caller must free after use */
>>  static const char *safe_name(struct kobject *kobj, const char *orig_name)
>>  {
>> @@ -164,6 +177,35 @@ int __of_add_property_sysfs(struct device_node *np, struct property *pp)
>>         return rc;
>>  }
>>
>> +/*
>> + * In the imported device tree (fdt), phandle is a property.  In the
>> + * internal data structure it is instead stored in the struct device_node.
>> + * Make phandle visible in sysfs as if it was a property.
>> + */
>> +int __of_add_phandle_sysfs(struct device_node *np)
>> +{
>> +       int rc;
>> +
>> +       if (!IS_ENABLED(CONFIG_SYSFS))
>> +               return 0;
>> +
>> +       if (!of_kset || !of_node_is_attached(np))
>> +               return 0;
>> +
>> +       if (!np->phandle || np->phandle == 0xffffffff)
>> +               return 0;
>> +
>> +       sysfs_bin_attr_init(&np->attr_phandle);
>> +       np->attr_phandle.attr.name = "phandle";
>> +       np->attr_phandle.attr.mode = 0444;
>> +       np->attr_phandle.size = sizeof(np->phandle);
>> +       np->attr_phandle.read = of_node_phandle_read;
>> +
>> +       rc = sysfs_create_bin_file(&np->kobj, &np->attr_phandle);
>> +       WARN(rc, "error adding attribute phandle to node %s\n", np->full_name);
>> +       return rc;
>> +}
>> +
>>  int __of_attach_node_sysfs(struct device_node *np)
>>  {
>>         const char *name;
>> @@ -193,6 +235,8 @@ int __of_attach_node_sysfs(struct device_node *np)
>>         if (rc)
>>                 return rc;
>>
>> +       __of_add_phandle_sysfs(np);
>> +
>>         for_each_property_of_node(np, pp)
>>                 __of_add_property_sysfs(np, pp);
>>
>> @@ -2097,9 +2141,7 @@ void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align))
>>                 int id, len;
>>
>>                 /* Skip those we do not want to proceed */
>> -               if (!strcmp(pp->name, "name") ||
>> -                   !strcmp(pp->name, "phandle") ||
>> -                   !strcmp(pp->name, "linux,phandle"))
>> +               if (!strcmp(pp->name, "name"))
>>                         continue;
>>
>>                 np = of_find_node_by_path(pp->value);
>> diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
>> index 888fdbc09992..59545b8fbf46 100644
>> --- a/drivers/of/dynamic.c
>> +++ b/drivers/of/dynamic.c
>> @@ -218,19 +218,6 @@ int of_property_notify(int action, struct device_node *np,
>>
>>  void __of_attach_node(struct device_node *np)
>>  {
>> -       const __be32 *phandle;
>> -       int sz;
>> -
>> -       np->name = __of_get_property(np, "name", NULL) ? : "<NULL>";
>> -       np->type = __of_get_property(np, "device_type", NULL) ? : "<NULL>";
>> -
>> -       phandle = __of_get_property(np, "phandle", &sz);
>> -       if (!phandle)
>> -               phandle = __of_get_property(np, "linux,phandle", &sz);
>> -       if (IS_ENABLED(CONFIG_PPC_PSERIES) && !phandle)
>> -               phandle = __of_get_property(np, "ibm,phandle", &sz);
>> -       np->phandle = (phandle && (sz >= 4)) ? be32_to_cpup(phandle) : 0;
>> -
>>         np->child = NULL;
>>         np->sibling = np->parent->child;
>>         np->parent->child = np;
>> @@ -243,11 +230,47 @@ void __of_attach_node(struct device_node *np)
>>  int of_attach_node(struct device_node *np)
>>  {
>>         struct of_reconfig_data rd;
>> +       struct property *prev;
>> +       struct property *prop;
>> +       struct property *save_next;
>>         unsigned long flags;
>> +       const __be32 *phandle;
>> +       int sz;
>>
>>         memset(&rd, 0, sizeof(rd));
>>         rd.dn = np;
>>
>> +       np->name = __of_get_property(np, "name", NULL) ? : "<NULL>";
>> +       np->type = __of_get_property(np, "device_type", NULL) ? : "<NULL>";
> 
> Why can't we just store NULL here? I know you're just moving this
> existing code, but now we have it twice. I assume there was some
> reason, so at least a comment why would be good. (I'm guessing it's
> because strcmp won't take a NULL).

Comment added.

(Yes, the users of the string pointer are not expecting NULL.)


>> +
>> +       phandle = __of_get_property(np, "phandle", &sz);
>> +       if (!phandle)
>> +               phandle = __of_get_property(np, "linux,phandle", &sz);
>> +       if (IS_ENABLED(CONFIG_PPC_PSERIES) && !phandle)
>> +               phandle = __of_get_property(np, "ibm,phandle", &sz);
>> +       np->phandle = (phandle && (sz >= 4)) ? be32_to_cpup(phandle) : 0;
>> +
>> +       /* remove phandle properties from node */
>> +       prev = NULL;
>> +       for (prop = np->properties; prop != NULL; ) {
>> +               save_next = prop->next;
>> +               if (!strcmp(prop->name, "phandle") ||
>> +                   !strcmp(prop->name, "ibm,phandle") ||
>> +                   !strcmp(prop->name, "linux,phandle")) {
>> +                       if (prev)
>> +                               prev->next = prop->next;
>> +                       else
>> +                               np->properties = prop->next;
>> +                       prop->next = np->deadprops;
>> +                       np->deadprops = prop;
>> +               } else {
>> +                       prev = prop;
>> +               }
>> +               prop = save_next;
>> +       }
>> +
>> +       __of_add_phandle_sysfs(np);
>> +
>>         mutex_lock(&of_mutex);
>>         raw_spin_lock_irqsave(&devtree_lock, flags);
>>         __of_attach_node(np);
>> @@ -429,6 +452,7 @@ struct device_node *__of_node_dup(const struct device_node *np, const char *fmt,
>>         /* Iterate over and duplicate all properties */
>>         if (np) {
>>                 struct property *pp, *new_pp;
>> +               node->phandle = np->phandle;
>>                 for_each_property_of_node(np, pp) {
>>                         new_pp = __of_prop_dup(pp, GFP_KERNEL);
>>                         if (!new_pp)
>> @@ -441,6 +465,10 @@ struct device_node *__of_node_dup(const struct device_node *np, const char *fmt,
>>                         }
>>                 }
>>         }
>> +
>> +       node->name = __of_get_property(node, "name", NULL) ? : "<NULL>";
>> +       node->type = __of_get_property(node, "device_type", NULL) ? : "<NULL>";
>> +
>>         return node;
>>
>>   err_prop:
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index e5ce4b59e162..270f31b0c259 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -181,6 +181,8 @@ static void populate_properties(const void *blob,
>>                 const __be32 *val;
>>                 const char *pname;
>>                 u32 sz;
>> +               int prop_is_phandle = 0;
>> +               int prop_is_ibm_phandle = 0;
> 
> Can be bool.

These two variables eliminated while addressing the next comment.


>>
>>                 val = fdt_getprop_by_offset(blob, cur, &pname, &sz);
>>                 if (!val) {
>> @@ -196,11 +198,6 @@ static void populate_properties(const void *blob,
>>                 if (!strcmp(pname, "name"))
>>                         has_name = true;
>>
>> -               pp = unflatten_dt_alloc(mem, sizeof(struct property),
>> -                                       __alignof__(struct property));
>> -               if (dryrun)
>> -                       continue;
>> -
>>                 /* We accept flattened tree phandles either in
>>                  * ePAPR-style "phandle" properties, or the
>>                  * legacy "linux,phandle" properties.  If both
>> @@ -208,23 +205,34 @@ static void populate_properties(const void *blob,
>>                  * will get weird. Don't do that.
>>                  */
>>                 if (!strcmp(pname, "phandle") ||
>> -                   !strcmp(pname, "linux,phandle")) {
>> -                       if (!np->phandle)
>> -                               np->phandle = be32_to_cpup(val);
>> -               }
>> +                   !strcmp(pname, "linux,phandle"))
>> +                       prop_is_phandle = 1;
>>
>>                 /* 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);
>> +               if (!strcmp(pname, "ibm,phandle")) {
>> +                       prop_is_phandle = 1;
>> +                       prop_is_ibm_phandle = 1;
>> +               }
>> +
>> +               if (!prop_is_phandle)
>> +                       pp = unflatten_dt_alloc(mem, sizeof(struct property),
>> +                                               __alignof__(struct property));
>>
>> -               pp->name   = (char *)pname;
>> -               pp->length = sz;
>> -               pp->value  = (__be32 *)val;
>> -               *pprev     = pp;
>> -               pprev      = &pp->next;
>> +               if (dryrun)
>> +                       continue;
>> +
>> +               if (!prop_is_phandle) {
>> +                       pp->name   = (char *)pname;
>> +                       pp->length = sz;
>> +                       pp->value  = (__be32 *)val;
>> +                       *pprev     = pp;
>> +                       pprev      = &pp->next;
>> +               } else if (prop_is_ibm_phandle || !np->phandle) {
> 
> This logic is a bit strange. I think it would be a bit better if we
> can keep all the phandle code together and end with a continue, then
> have the property handling code at the end of the loop.

I will do this.  One side effect will be that the value of property
"ibm,phandle" will no longer override the value of properties "phandle"
and "linux,phandle".


>> +                       np->phandle = be32_to_cpup(val);
>> +               }
>>         }
>>
>>         /* With version 0x10 we may not have the name property,
>> diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
>> index 18bbb4517e25..33f11a5384f3 100644
>> --- a/drivers/of/of_private.h
>> +++ b/drivers/of/of_private.h
>> @@ -47,6 +47,7 @@ extern int of_property_notify(int action, struct device_node *np,
>>  extern void of_node_release(struct kobject *kobj);
>>  extern int __of_changeset_apply(struct of_changeset *ocs);
>>  extern int __of_changeset_revert(struct of_changeset *ocs);
>> +extern int __of_add_phandle_sysfs(struct device_node *np);
>>  #else /* CONFIG_OF_DYNAMIC */
>>  static inline int of_property_notify(int action, struct device_node *np,
>>                                      struct property *prop, struct property *old_prop)
>> diff --git a/drivers/of/overlay.c b/drivers/of/overlay.c
>> index 7827786718d8..ca0b85f5deb1 100644
>> --- a/drivers/of/overlay.c
>> +++ b/drivers/of/overlay.c
>> @@ -101,9 +101,7 @@ static int of_overlay_apply_single_property(struct of_overlay *ov,
>>         tprop = of_find_property(target, prop->name, NULL);
>>
>>         /* special properties are not meant to be updated (silent NOP) */
>> -       if (of_prop_cmp(prop->name, "name") == 0 ||
>> -           of_prop_cmp(prop->name, "phandle") == 0 ||
>> -           of_prop_cmp(prop->name, "linux,phandle") == 0)
>> +       if (!of_prop_cmp(prop->name, "name"))
>>                 return 0;
>>
>>         propn = __of_prop_dup(prop, GFP_KERNEL);
>> diff --git a/drivers/of/resolver.c b/drivers/of/resolver.c
>> index 7ae9863cb0a4..624cbaeae0a4 100644
>> --- a/drivers/of/resolver.c
>> +++ b/drivers/of/resolver.c
>> @@ -71,30 +71,11 @@ static void adjust_overlay_phandles(struct device_node *overlay,
>>                 int phandle_delta)
>>  {
>>         struct device_node *child;
>> -       struct property *prop;
>> -       phandle phandle;
>>
>>         /* adjust node's phandle in node */
>>         if (overlay->phandle != 0 && overlay->phandle != OF_PHANDLE_ILLEGAL)
>>                 overlay->phandle += phandle_delta;
>>
>> -       /* copy adjusted phandle into *phandle properties */
>> -       for_each_property_of_node(overlay, prop) {
>> -
>> -               if (of_prop_cmp(prop->name, "phandle") &&
>> -                   of_prop_cmp(prop->name, "linux,phandle"))
>> -                       continue;
>> -
>> -               if (prop->length < 4)
>> -                       continue;
>> -
>> -               phandle = be32_to_cpup(prop->value);
>> -               if (phandle == OF_PHANDLE_ILLEGAL)
>> -                       continue;
>> -
>> -               *(uint32_t *)prop->value = cpu_to_be32(overlay->phandle);
>> -       }
>> -
>>         for_each_child_of_node(overlay, child)
>>                 adjust_overlay_phandles(child, phandle_delta);
>>  }
>> @@ -197,9 +178,7 @@ static int adjust_local_phandle_references(struct device_node *local_fixups,
>>         for_each_property_of_node(local_fixups, prop_fix) {
>>
>>                 /* skip properties added automatically */
>> -               if (!of_prop_cmp(prop_fix->name, "name") ||
>> -                   !of_prop_cmp(prop_fix->name, "phandle") ||
>> -                   !of_prop_cmp(prop_fix->name, "linux,phandle"))
>> +               if (!of_prop_cmp(prop_fix->name, "name"))
>>                         continue;
>>
>>                 if ((prop_fix->length % 4) != 0 || prop_fix->length == 0)
>> diff --git a/include/linux/of.h b/include/linux/of.h
>> index 21e6323de0f3..4e86e05853f3 100644
>> --- a/include/linux/of.h
>> +++ b/include/linux/of.h
>> @@ -61,6 +61,7 @@ struct device_node {
>>         struct  kobject kobj;
>>         unsigned long _flags;
>>         void    *data;
>> +       struct bin_attribute attr_phandle;
>>  #if defined(CONFIG_SPARC)
>>         const char *path_component_name;
>>         unsigned int unique_id;
>> --
>> Frank Rowand <frank.rowand@xxxxxxxx>

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