Stephen Warren <swarren@xxxxxxxxxxxxx> wrote @ Thu, 21 Nov 2013 19:57:00 +0100: > On 11/21/2013 10:17 AM, Hiroshi Doyu wrote: > > Iterating over a property containing a list of phandles with arguments > > is a common operation for device drivers. This patch adds a new > > of_property_for_each_phandle_with_args() macro to make the iteration > > simpler. > > > > Signed-off-by: Hiroshi Doyu <hdoyu@xxxxxxxxxx> > > --- > > v6+: > > Use the description, which Grant Likely proposed, to be full enough > > that a future reader can figure out why a patch was written. > > http://lists.linuxfoundation.org/pipermail/iommu/2013-November/007062.html > > This new version only addresses one of the concerns that Grant had, > namely the commit message. > > > diff --git a/include/linux/of.h b/include/linux/of.h > > > +#define of_property_for_each_phandle_with_args(np, list, cells, i, args) \ > > + for (i = 0; !of_parse_phandle_with_args(np, list, cells, i, args); i++) > > + > > Grant also wanted the actual implementation fixed so that it wasn't so > inefficient. > > What this current patch does is basically: > > for every entry in the property: > for every entry in the property before the current index: > parse the phandle+specifier > > That's roughly O(n^2). (n is # entries in the property) > > Instead, what should happen is: > > for every entry in the property: > parse the phandle+specifier > yield the result > > That's roughly O(n). > > In other words, an implementation more along the lines of > include/linux/of.h's: > > #define of_property_for_each_u32(np, propname, prop, p, u) \ > for (prop = of_find_property(np, propname, NULL), \ > p = of_prop_next_u32(prop, NULL, &u); \ > p; \ > p = of_prop_next_u32(prop, p, &u)) > > ... so you'd need functions like of_prop_first_specifier() and > of_prop_next_specifier(), and perhaps some associated set of state > variables, perhaps with all the state wrapped into a single struct for > simplicity. Although I couldn't invent any struct to hold params and state here, I'd like you to review the following interface is ok or not. At first, I thought to refactor __of_parse_phandle_with_args() but it's a bit highly optimized by Stephen and it looked a bit hard to refactor without perf regressions. Instread, I introduced 2 new functions "of_parse_{first,next}_phandle_with_args()" to parse phandles. If this interface is ok, I'll include this into the next v7 series. -----8<-----8<-----8<-----8<-----8<-----8<-----8<-----8<-----8<----- From: Hiroshi Doyu <hdoyu@xxxxxxxxxx> Iterating over a property containing a list of phandles with arguments is a common operation for device drivers. This patch adds a new of_property_for_each_phandle_with_args() macro to make the iteration simpler. Introduced "of_parse_{first,next}_phandle_with_args()", where "const __be32 **list" is used to hold the next list to be processed as a state pramameter, and both "of_parse_{first,next}_phandle_with_args()" returns the remaining list in the number of cell(4 byte). If any error happens, "list" is set NULL not to proceed the rest. Signed-off-by: Hiroshi Doyu <hdoyu@xxxxxxxxxx> --- v6++: Optimized to avoid O(n^2), suggested by Stephen Warren. http://lists.linuxfoundation.org/pipermail/iommu/2013-November/007066.html v6+: Use the description, which Grant Likely proposed, to be full enough that a future reader can figure out why a patch was written. v5: New patch for v5. Signed-off-by: Hiroshi Doyu <hdoyu@xxxxxxxxxx> --- drivers/of/base.c | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/of.h | 52 ++++++++++++++++++++++++++++++++++ 2 files changed, 134 insertions(+) diff --git a/drivers/of/base.c b/drivers/of/base.c index f807d0e..3e29b10 100644 --- a/drivers/of/base.c +++ b/drivers/of/base.c @@ -1201,6 +1201,88 @@ void of_print_phandle_args(const char *msg, const struct of_phandle_args *args) printk("\n"); } +int __of_parse_next_phandle_with_args(const __be32 **plist, + const char *cells_name, int cell_count, + struct of_phandle_args *out_args) +{ + phandle phandle; + int i, count = 0, err; + struct device_node *dn; + const __be32 *list; + + BUG_ON(!out_args); + BUG_ON(!cells_name && !cell_count); + + /* + * "*plist" should hold phandle, and it's updated to the next + * phandle at return if no error. + */ + list = *plist; + out_args->np = NULL; + + phandle = be32_to_cpup(list); + if (!phandle) + goto err_out; + + dn = of_find_node_by_phandle(phandle); + if (!dn) + goto err_out; + + if (cells_name) { + err = of_property_read_u32(dn, cells_name, &count); + if (err) + goto err_out; + } else { + count = cell_count; + } + + out_args->np = dn; + out_args->args_count = count; + for (i = 0; i < count; i++) + out_args->args[i] = be32_to_cpup(list + 1 + i); + + *plist = list + count + 1; /* update to the next list */ + return count + 1; + +err_out: + *plist = NULL; + return -EINVAL; +} +EXPORT_SYMBOL_GPL(__of_parse_next_phandle_with_args); + +int __of_parse_first_phandle_with_args(const struct device_node *np, + const __be32 **out_list, + const char *list_name, + const char *cells_name, + int cell_count, + struct of_phandle_args *out_args) +{ + int rem, count; + const __be32 *list; + + list = of_get_property(np, list_name, &rem); + if (!list) + goto err_out; + + rem /= sizeof(*list); + if (!rem) + goto err_out; + + count = __of_parse_next_phandle_with_args(&list, cells_name, + cell_count, out_args); + if (!list) + goto err_out; + + rem -= count; + *out_list = list; /* update to the next list */ + return rem; + +err_out: + *out_list = NULL; + return -EINVAL; +} +EXPORT_SYMBOL_GPL(__of_parse_first_phandle_with_args); + static int __of_parse_phandle_with_args(const struct device_node *np, const char *list_name, const char *cells_name, diff --git a/include/linux/of.h b/include/linux/of.h index 276c546..9f15622 100644 --- a/include/linux/of.h +++ b/include/linux/of.h @@ -303,6 +303,35 @@ extern int of_parse_phandle_with_fixed_args(const struct device_node *np, extern int of_count_phandle_with_args(const struct device_node *np, const char *list_name, const char *cells_name); +extern int __of_parse_first_phandle_with_args(const struct device_node *np, + const __be32 **out_list, + const char *list_name, + const char *cells_name, + int cell_count, + struct of_phandle_args *out_args); + +extern int __of_parse_next_phandle_with_args(const __be32 **plist, + const char *cells_name, + int cell_count, + struct of_phandle_args *out_args); + +static inline int of_parse_first_phandle_with_args(const struct device_node *np, + const __be32 **out_list, + const char *list_name, + const char *cells_name, + struct of_phandle_args *out_args) +{ + return __of_parse_first_phandle_with_args(np, out_list, list_name, + cells_name, 0, out_args); +} + +static inline int of_parse_next_phandle_with_args(const __be32 **plist, + const char *cells_name, + struct of_phandle_args *out_args) +{ + return __of_parse_next_phandle_with_args(plist, cells_name, 0, out_args); +} + extern void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align)); extern int of_alias_get_id(struct device_node *np, const char *stem); @@ -527,6 +556,24 @@ static inline int of_count_phandle_with_args(struct device_node *np, return -ENOSYS; } +static inline int __of_parse_first_phandle_with_args( + const struct device_node *np, const __be32 **out_list, + const char *list_name, const char *cells_name, int cell_count, + struct of_phandle_args *out_args) +{ + *out_list = NULL; + return -ENOSYS; +} + + +static inline int __of_parse_next_phandle_with_args( + const __be32 **plist, const char *cells_name, int cell_count, + struct of_phandle_args *out_args) +{ + *plist = NULL; + return -ENOSYS; +} + static inline int of_alias_get_id(struct device_node *np, const char *stem) { return -ENOSYS; @@ -613,6 +660,11 @@ static inline int of_property_read_u32(const struct device_node *np, s; \ s = of_prop_next_string(prop, s)) +#define of_property_for_each_phandle_with_args(node, list, list_name, cells_name, rem, args) \ + for (rem = of_parse_first_phandle_with_args(node, &list, list_name, cells_name, &args); \ + list && rem >= 0; \ + rem -= of_parse_next_phandle_with_args(&list, cells_name, &args)) + #if defined(CONFIG_PROC_FS) && defined(CONFIG_PROC_DEVICETREE) extern void proc_device_tree_add_node(struct device_node *, struct proc_dir_entry *); extern void proc_device_tree_add_prop(struct proc_dir_entry *pde, struct property *prop); -- 1.8.1.5 -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
