Re: [PATCH 12/19] xen/dt: Move bootfdt functions to xen/bootfdt.h

[Alejandro Vallejo <agarciav@amd.com>]

On Sat May 31, 2025 at 2:35 AM CEST, dmkhn wrote:
> On Fri, May 30, 2025 at 02:02:20PM +0200, Alejandro Vallejo wrote:
>> Part of an unpicking process to extract bootfdt contents independent of bootinfo
>> to a separate file for x86 to take.
>> 
>> Move functions required for early FDT parsing from device_tree.h and arm's
>> setup.h onto bootfdt.h
>> 
>> Declaration motion only. Not a functional change.
>> 
>> Signed-off-by: Alejandro Vallejo <agarciav@amd.com>
>> ---
>>  xen/arch/arm/include/asm/setup.h |  6 ----
>>  xen/include/xen/bootfdt.h        | 62 ++++++++++++++++++++++++++++++++
>>  xen/include/xen/device_tree.h    | 34 +-----------------
>>  3 files changed, 63 insertions(+), 39 deletions(-)
>> 
>> diff --git a/xen/arch/arm/include/asm/setup.h b/xen/arch/arm/include/asm/setup.h
>> index 0f9e531a34..32308837a9 100644
>> --- a/xen/arch/arm/include/asm/setup.h
>> +++ b/xen/arch/arm/include/asm/setup.h
>> @@ -55,12 +55,6 @@ void setup_mm(void);
>>  extern uint32_t hyp_traps_vector[];
>>  void init_traps(void);
>> 
>> -void device_tree_get_reg(const __be32 **cell, uint32_t address_cells,
>> -                         uint32_t size_cells, paddr_t *start, paddr_t *size);
>> -
>> -u32 device_tree_get_u32(const void *fdt, int node,
>> -                        const char *prop_name, u32 dflt);
>> -
>>  int handle_device(struct domain *d, struct dt_device_node *dev, p2m_type_t p2mt,
>>                    struct rangeset *iomem_ranges, struct rangeset *irq_ranges);
>> 
>> diff --git a/xen/include/xen/bootfdt.h b/xen/include/xen/bootfdt.h
>> index fa65e8fcf4..079259c719 100644
>> --- a/xen/include/xen/bootfdt.h
>> +++ b/xen/include/xen/bootfdt.h
>> @@ -2,6 +2,7 @@
>>  #ifndef XEN_BOOTFDT_H
>>  #define XEN_BOOTFDT_H
>> 
>> +#include <xen/byteorder.h>
>>  #include <xen/types.h>
>>  #include <xen/kernel.h>
>>  #include <xen/macros.h>
>> @@ -16,8 +17,53 @@
>>  #define NR_MEM_BANKS 256
>>  #define NR_SHMEM_BANKS 32
>> 
>> +/* Default #address and #size cells */
>> +#define DT_ROOT_NODE_ADDR_CELLS_DEFAULT 2
>> +#define DT_ROOT_NODE_SIZE_CELLS_DEFAULT 1
>> +
>>  #define MAX_MODULES 32 /* Current maximum useful modules */
>> 
>> +#define DEVICE_TREE_MAX_DEPTH 16
>> +
>> +/* Helper to read a big number; size is in cells (not bytes) */
>> +static inline u64 dt_read_number(const __be32 *cell, int size)
>> +{
>> +    u64 r = 0;
>> +
>> +    while ( size-- )
>> +        r = (r << 32) | be32_to_cpu(*(cell++));
>> +    return r;
>> +}
>> +
>> +static inline u64 dt_next_cell(int s, const __be32 **cellp)
>> +{
>> +    const __be32 *p = *cellp;
>> +
>> +    *cellp = p + s;
>> +    return dt_read_number(p, s);
>> +}
>> +
>> +typedef int (*device_tree_node_func)(const void *fdt,
>> +                                     int node, const char *name, int depth,
>> +                                     u32 address_cells, u32 size_cells,
>> +                                     void *data);
>> +
>> +/**
>> + * device_tree_for_each_node - iterate over all device tree sub-nodes
>> + * @fdt: flat device tree.
>> + * @node: parent node to start the search from
>> + * @func: function to call for each sub-node.
>> + * @data: data to pass to @func.
>> + *
>> + * Any nodes nested at DEVICE_TREE_MAX_DEPTH or deeper are ignored.
>> + *
>> + * Returns 0 if all nodes were iterated over successfully.  If @func
>> + * returns a value different from 0, that value is returned immediately.
>> + */
>> +int device_tree_for_each_node(const void *fdt, int node,
>> +                              device_tree_node_func func,
>> +                              void *data);
>> +
>>  typedef enum {
>>      BOOTMOD_XEN,
>>      BOOTMOD_FDT,
>> @@ -246,4 +292,20 @@ static inline struct membanks *membanks_xzalloc(unsigned int nr,
>>      return banks;
>>  }
>> 
>> +/*
>> + * Interpret the property `prop_name` of `node` as a u32.
>> + *
>> + * Returns the property value on success; otherwise returns `dflt`.
>> + */
>> +uint32_t device_tree_get_u32(const void *fdt, int node,
>> +                             const char *prop_name, uint32_t dflt);
>
> Suggest using `dt_` prefix (or any other good prefix) for all functions
> in this header for consistency: e.g. there's dt_read_number() but also
> device_tree_get_u32().

I'd be quite happy with an fdt_ prefix, to clearly show they relate to FDTs.

But I didn't want to do that right away because it would obscure the strict code
motion that's going on.

>
>> +
>> +/*
>> + * Interpret the property `prop_name` of `node` as a "reg".
>> + *
>> + * Returns outputs in `start` and `size`.
>> + */
>> +void device_tree_get_reg(const __be32 **cell, uint32_t address_cells,
>> +                         uint32_t size_cells, paddr_t *start, paddr_t *size);
>> +
>>  #endif /* XEN_BOOTFDT_H */
>> diff --git a/xen/include/xen/device_tree.h b/xen/include/xen/device_tree.h
>> index 6dc1fb5159..0a22b1ba1d 100644
>> --- a/xen/include/xen/device_tree.h
>> +++ b/xen/include/xen/device_tree.h
>> @@ -10,6 +10,7 @@
>>  #ifndef __XEN_DEVICE_TREE_H__
>>  #define __XEN_DEVICE_TREE_H__
>> 
>> +#include <xen/bootfdt.h>
>>  #include <xen/byteorder.h>
>> 
>>  #include <asm/device.h>
>> @@ -22,8 +23,6 @@
>>  #include <xen/list.h>
>>  #include <xen/rwlock.h>
>> 
>> -#define DEVICE_TREE_MAX_DEPTH 16
>> -
>>  /*
>>   * Struct used for matching a device
>>   */
>> @@ -164,17 +163,8 @@ struct dt_raw_irq {
>>      u32 specifier[DT_MAX_IRQ_SPEC];
>>  };
>> 
>> -typedef int (*device_tree_node_func)(const void *fdt,
>> -                                     int node, const char *name, int depth,
>> -                                     u32 address_cells, u32 size_cells,
>> -                                     void *data);
>> -
>>  extern const void *device_tree_flattened;
>> 
>> -int device_tree_for_each_node(const void *fdt, int node,
>> -                              device_tree_node_func func,
>> -                              void *data);
>> -
>>  /**
>>   * dt_unflatten_host_device_tree - Unflatten the host device tree
>>   *
>> @@ -245,10 +235,6 @@ void intc_dt_preinit(void);
>>  #define dt_node_cmp(s1, s2) strcasecmp((s1), (s2))
>>  #define dt_compat_cmp(s1, s2) strcasecmp((s1), (s2))
>> 
>> -/* Default #address and #size cells */
>> -#define DT_ROOT_NODE_ADDR_CELLS_DEFAULT 2
>> -#define DT_ROOT_NODE_SIZE_CELLS_DEFAULT 1
>> -
>>  #define dt_for_each_property_node(dn, pp)                   \
>>      for ( pp = (dn)->properties; (pp) != NULL; pp = (pp)->next )
>> 
>> @@ -258,16 +244,6 @@ void intc_dt_preinit(void);
>>  #define dt_for_each_child_node(dt, dn)                      \
>>      for ( dn = (dt)->child; (dn) != NULL; dn = (dn)->sibling )
>> 
>> -/* Helper to read a big number; size is in cells (not bytes) */
>> -static inline u64 dt_read_number(const __be32 *cell, int size)
>> -{
>> -    u64 r = 0;
>> -
>> -    while ( size-- )
>> -        r = (r << 32) | be32_to_cpu(*(cell++));
>> -    return r;
>> -}
>> -
>>  /* Wrapper for dt_read_number() to return paddr_t (instead of uint64_t) */
>>  static inline paddr_t dt_read_paddr(const __be32 *cell, int size)
>>  {
>> @@ -307,14 +283,6 @@ static inline int dt_size_to_cells(int bytes)
>>      return (bytes / sizeof(u32));
>>  }
>> 
>> -static inline u64 dt_next_cell(int s, const __be32 **cellp)
>> -{
>> -    const __be32 *p = *cellp;
>> -
>> -    *cellp = p + s;
>> -    return dt_read_number(p, s);
>> -}
>> -
>>  static inline const char *dt_node_full_name(const struct dt_device_node *np)
>>  {
>>      return (np && np->full_name) ? np->full_name : "<no-node>";
>> --
>> 2.43.0
>> 
>>