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

["Orzel, Michal" <michal.orzel@xxxxxxx>]

On 31/05/2025 02:35, dmkhn@xxxxxxxxx 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@xxxxxxx>
>> ---
>>  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().
Not really. AFAIR device_tree_ prefix is for functions operating on flattened DT
(usually calling libfdt functions inside) and dt_ otherwise. Let's not mix them.

~Michal