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

[Rob Herring]

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).

> +
> +       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.

>
>                 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.

> +                       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>
>