Re: [PATCH v15 06/16] of/fdt: add helper functions for handling properties

[Frank Rowand]

On 10/04/18 22:06, AKASHI, Takahiro wrote:
> Frank,
> 
> # I haven't reply to your comments.
> 
> On Fri, Sep 28, 2018 at 02:13:58PM -0700, Frank Rowand wrote:
>> On 09/28/18 06:44, Rob Herring wrote:
>>> +David Gibson
>>>
>>> On Fri, Sep 28, 2018 at 1:48 AM AKASHI Takahiro
>>> <takahiro.akashi@xxxxxxxxxx> wrote:
>>>>
>>>> These functions will be used later to handle kexec-specific properties
>>>> in arm64's kexec_file implementation.
>>
>> As I requested in version 14:
>>
>>   The intent of the helper functions is related to properties whose values are
>>    tuples of the same format as the "reg" property of the "/memory" nodes.  For
>>    example, the "linux,usable-memory-range" and "linux,elfcoredhr" properties of
>>    the "/chosen" node.
>>
>>    The patch header and the function names should be updated to reflect this intent.
> 
> I agree regarding the patch header.
> 
>>
>>>>
>>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
>>>> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
>>>> Cc: Frank Rowand <frowand.list@xxxxxxxxx>
>>>> Cc: devicetree@xxxxxxxxxxxxxxx
>>>> ---
>>
>> Missing list of changes since version 14.
> 
> Sorry for the inconvenience, but a whole change list goes into
> the cover letter, not individual patches.

That works for me, but please add us to the distro list for the cover letter.


>>>>  drivers/of/fdt.c       | 56 ++++++++++++++++++++++++++++++++++++++++++
>>>>  include/linux/of_fdt.h |  4 +++
>>>>  2 files changed, 60 insertions(+)
>>>>
>>>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>>>> index 800ad252cf9c..c65c31562ccb 100644
>>>> --- a/drivers/of/fdt.c
>>>> +++ b/drivers/of/fdt.c
>>>> @@ -25,6 +25,7 @@
>>>>  #include <linux/debugfs.h>
>>>>  #include <linux/serial_core.h>
>>>>  #include <linux/sysfs.h>
>>>> +#include <linux/types.h>
>>>>
>>>>  #include <asm/setup.h>  /* for COMMAND_LINE_SIZE */
>>>>  #include <asm/page.h>
>>>> @@ -1323,3 +1324,58 @@ late_initcall(of_fdt_raw_init);
>>>>  #endif
>>>>
>>>>  #endif /* CONFIG_OF_EARLY_FLATTREE */
>>
>> In v14 I requested:
>>
>>    Please add comment:
>>
>>    /* helper functions for arm64 kexec */
> 
> Okay.
> 
>>
>>>> +
>>>> +#define FDT_ALIGN(x, a)        (((x) + (a) - 1) & ~((a) - 1))
>>>> +#define FDT_TAGALIGN(x)        (FDT_ALIGN((x), FDT_TAGSIZE))
>>>> +
>>>> +int fdt_prop_len(const char *prop_name, int len)
>>
>> In v14, I requested:
>>
>>    Please rename as fdt_len_added_prop()
> 
> Anyhow, I will drop this function, preferring to new
> fdt_[address|size]_cells().
> 
>> I'm not really happy with my suggested name, but do not have a
>> better one yet.  As Rob notes, maybe David G will have a helpful
>> comment.
>>
>>>> +{
>>>> +       return (strlen(prop_name) + 1) +
>>>> +               sizeof(struct fdt_property) +
>>>> +               FDT_TAGALIGN(len);
>>>
>>> Looks like you are using this to calculate how much space you need to
>>> allocate in addition to the current DTB for a couple of new or
>>> replaced properties. I'm not sure that this calculation is completely
>>> accurate. And it is strange there doesn't seem to be any libfdt
>>> function for this already. It would be simpler to just add some fixed
>>> additional amount.
>>>
>>> Maybe David G has comments on this?
> 
> I'm not quit sure why it's not that accurate, but as I said in a reply to
> David's comment, I will take your suggestion.
> 
>>>> +}
>>>> +
>>>
>>> The rest of this should go in drivers/of/fdt_address.c. Ultimately, it
>>> should go into libfdt, but I'm fine with having it in the kernel for
>>> now.
>>>
>>>> +static void fill_property(void *buf, u64 val64, int cells)
>>
>> In v14 I requested:
>>
>> Please rename as cpu64_to_fdt_cells()
> 
> I don't mind, but this function may be dropped if Rob sticks to
> u-boot's fdt_pack_reg() over my fdt_setprop_reg().

I have another comment a couple of minutes ago in the longer thread
about this function.


>>
>>>> +{
>>>> +       __be32 val32;
>>>> +
>>>> +       while (cells) {
>>>> +               val32 = cpu_to_fdt32((val64 >> (32 * (--cells))) & U32_MAX);
>>>> +               memcpy(buf, &val32, sizeof(val32));
>>>> +               buf += sizeof(val32);
>>>
>>> This is kind of hard to read. I would copy u-boot's fdt_pack_reg function.
>>>
>>> BTW, for purposes of moving to libfdt, we'll need the authors'
>>> (Masahiro Yamada and Hans de Goede) permission to dual license.
>>>
>>>> +       }
>>>> +}
>>>> +
>>>> +int fdt_setprop_reg(void *fdt, int nodeoffset, const char *name,
>>>> +                                               u64 addr, u64 size)
>>>> +{
>>>> +       int addr_cells, size_cells;
>>
>> unsigned
> 
> fdt_[address|size]_cell() returns an int.

I stand corrected.  They take advantage of the fact that valid values
are in the range 0..4 and return a negative value for error.


>>>> +       char buf[sizeof(__be32) * 2 * 2];
>>>> +               /* assume dt_root_[addr|size]_cells <= 2 */
>>>> +       void *prop;
>>>> +       size_t buf_size;
>>>> +
>>>> +       addr_cells = fdt_address_cells(fdt, 0);
>>>> +       if (addr_cells < 0)
>>>> +               return addr_cells;
>>>> +       size_cells = fdt_size_cells(fdt, 0);
>>>> +       if (size_cells < 0)
>>>> +               return size_cells;
>>>> +
>>>> +       /* if *_cells >= 2, cells can hold 64-bit values anyway */
>>>> +       if ((addr_cells == 1) && (addr > U32_MAX))
>>>> +               return -FDT_ERR_BADVALUE;
>>>> +
>>>> +       if ((size_cells == 1) && (size > U32_MAX))
>>>> +               return -FDT_ERR_BADVALUE;
>>
>> In v14 I requested:
>>
>>    Should also check that base + size does not wrap around.
> 
> Okay, I will start discussion, as you have suggested, in devicetree-spec ML.
> 
> Thanks,
> -Takahiro Akashi
> 
>>
>>>> +
>>>> +       buf_size = (addr_cells + size_cells) * sizeof(u32);
>>>> +       prop = buf;
>>>> +
>>>> +       fill_property(prop, addr, addr_cells);
>>>> +       prop += addr_cells * sizeof(u32);
>>>> +
>>>> +       fill_property(prop, size, size_cells);
>>>> +
>>>> +       return fdt_setprop(fdt, nodeoffset, name, buf, buf_size);
>>>> +}
>>>> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
>>>> index b9cd9ebdf9b9..842af6ea92ea 100644
>>>> --- a/include/linux/of_fdt.h
>>>> +++ b/include/linux/of_fdt.h
>>>> @@ -108,5 +108,9 @@ static inline void unflatten_device_tree(void) {}
>>>>  static inline void unflatten_and_copy_device_tree(void) {}
>>>>  #endif /* CONFIG_OF_EARLY_FLATTREE */
>>>>
>>>> +int fdt_prop_len(const char *prop_name, int len);
>>>> +int fdt_setprop_reg(void *fdt, int nodeoffset, const char *name,
>>>> +                                               u64 addr, u64 size);
>>>> +
>>>>  #endif /* __ASSEMBLY__ */
>>>>  #endif /* _LINUX_OF_FDT_H */
>>>> --
>>>> 2.19.0
>>>>
>>>
>>
>