Re: [PATCH v14 06/16] of/fdt: add helper functions for handling properties

From: Frank Rowand
Date: Wed Sep 26 2018 - 04:10:38 EST

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In reply to: AKASHI Takahiro: "Re: [PATCH v14 06/16] of/fdt: add helper functions for handling properties"
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Hi Rob,

On 09/25/18 22:57, AKASHI Takahiro wrote:
> Frank,
>
> On Fri, Sep 14, 2018 at 10:19:38AM -0700, Frank Rowand wrote:
>> On 09/13/18 18:26, Frank Rowand wrote:
>>> I was re-reading this while answering a later email in the thread. After reading
>>> other patches in the series that were not sent to me, I have a better understanding
>>> of the intent behind this patch, and some changes to my previous reply.
>>>
>>> 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.
>>> This means most or all of my previous suggested function name changes are no longer
>>> useful.
>>>
>>> Please add devicetree@xxxxxxxxxxxxxxx to the next version of this patch and to
>>> the patches that use the functions in this patch.
>>>
>>>
>>> On 09/07/18 12:53, Frank Rowand wrote:
>>>> On 09/07/18 01:00, AKASHI Takahiro wrote:
>>>>> These functions will be used later to handle kexec-specific properties
>>>>> in arm64's kexec_file implementation.
>>>>>
>>>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
>>>>> Cc: Rob Herring <robh+dt@xxxxxxxxxx>
>>>>> Cc: Frank Rowand <frowand.list@xxxxxxxxx>
>>>>> ---
>>>>> drivers/of/fdt.c | 62 ++++++++++++++++++++++++++++++++++++++++--
>>>>> include/linux/of_fdt.h | 10 +++++--
>>>>> 2 files changed, 68 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>>>>> index 800ad252cf9c..dc960cea1355 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>
>>>>> @@ -537,8 +538,8 @@ void *of_fdt_unflatten_tree(const unsigned long *blob,
>>>>> EXPORT_SYMBOL_GPL(of_fdt_unflatten_tree);
>>>>>
>>>>> /* Everything below here references initial_boot_params directly. */
>>>>> -int __initdata dt_root_addr_cells;
>>>>> -int __initdata dt_root_size_cells;
>>>>> +int dt_root_addr_cells;
>>>>> +int dt_root_size_cells;
>>>>>
>>>>> void *initial_boot_params;
>>>>>
>>>>> @@ -1323,3 +1324,60 @@ late_initcall(of_fdt_raw_init);
>>>>> #endif
>>>>>
>>>>> #endif /* CONFIG_OF_EARLY_FLATTREE */
>>>>> +
>>>
>>> Global comment: this code should not be using the variables
>>> dt_root_addr_cells and dt_root_size_cells. These variables are
>>> __initdata.
>>>
>>> The code that is using these helpers is acting upon a specific FDT
>>> (copied from initial_boot_params). This code should be getting the
>>> values of the root node's "#address-cells" and "#size-cells" from
>>> the FDT.
>>

Can you confirm whether "[PATCH 3/3] scripts/dtc: ..." (see below) will
be in the v4.20 pull request?

>> There will be new functions available soon to return the values of
>> a node's "#address-cells" and "#size-cells" from an fdt. They are
>> fdt_address_cells() and fdt_size_cells().
>>
>> Rob submitted the patch to add them yesterday in "[PATCH 3/3] scripts/dtc:
>> Update to upstream version v1.4.7-14-gc86da84d30e4" [1]
>
> Will this patch go into mainline in v4.20 merge window?
>
>> [1] https://lkml.kernel.org/r/<20180913202828.15372-3-robh@xxxxxxxxxx>
>
> Unfortunately, fdt_addresses.c where fdt_address_cells() and
> fdt_size_cells() are defined is NOT compiled in the kernel.
> I will submit a patch.
>
> -Takahiro Akashi
>
>
>> -Frank

Thanks,

Frank

>>
>>
>>>
>>>
>>>> Please add comment:
>>>>
>>>> /* helper functions for arm64 kexec */
>>>>
>>>>
>>>>> +bool of_fdt_cells_size_fitted(u64 base, u64 size)
>>>>
>>>> Please rename as of_fdt_range_valid()
>>>
>>> I'm not entirely sure of what the caller in 12/16 is trying to ensure
>>> with this function.
>>>
>>> (1) At the minimum (and what the implementation in of_fdt_cells_size_fitted()
>>> does) is make sure that an address and size tuple are consistent with
>>> the root properties "#address-cells" and "#size-cells".
>>>
>>> The caller in 12/16 is using this check to validate values for the
>>> properties "linux,elfcorehdr" and "linux,usable-memory-range".
>>>
>>> (2) A more complete check _might_ be to ensure that the values also
>>> specify memory that is available to the kernel. This memory is described
>>> by the "reg" property of one or more "/memory" nodes.
>>>
>>> This second check is probably what is actually desired.
>>>
>>> One possible issue to note is that the binding for "linux,usable-memory-range"
>>> suggests that available memory could be described by an EFI memory map.
>>> I am not familiar with how or when an EFI memory map might exist instead
>>> of the "/memory" nodes.
>>>
>>>
>>>>> +{
>>>>> + /* if *_cells >= 2, cells can hold 64-bit values anyway */
>>>>> + if ((dt_root_addr_cells == 1) && (base > U32_MAX))
>>>>> + return false;
>>>>> +
>>>>> + if ((dt_root_size_cells == 1) && (size > U32_MAX))
>>>>> + return false;
>>>>
>>>> Should also check that base + size does not wrap around.
>>>>
>>>>
>>>>> +
>>>>> + return true;
>>>>> +}
>>>>> +
>>>>> +size_t of_fdt_reg_cells_size(void)
>>>>
>>>> Please rename as of_fdt_root_range_size()
>>>
>>> Even better would be to remove this function and replace the one place
>>> that it is called from with the one line of code in this function.
>>>
>>> -Frank
>>>
>>>
>>>>> +{
>>>>> + return (dt_root_addr_cells + dt_root_size_cells) * sizeof(u32);
>>>>> +}
>>>>> +
>>>>> +#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)
>>>>
>>>> Please rename as fdt_len_added_prop()
>>>>
>>>>
>>>>> +{
>>>>> + return (strlen(prop_name) + 1) +
>>>>> + sizeof(struct fdt_property) +
>>>>> + FDT_TAGALIGN(len);
>>>>> +}
>>>>> +
>>>>
>>>> Please add comment, something like:
>>>>
>>>> /* cells must be 1 or 2 */
>>>>
>>>>
>>>>> +static void fill_property(void *buf, u64 val64, int cells)
>>>>
>>>> Please rename as cpu64_to_fdt_cells()
>>>>
>>>> Thanks,
>>>>
>>>> Frank
>>>>
>>>>> +{
>>>>> + __be32 val32;
>>>>> +
>>>>> + while (cells) {
>>>>> + val32 = cpu_to_fdt32((val64 >> (32 * (--cells))) & U32_MAX);
>>>>> + memcpy(buf, &val32, sizeof(val32));
>>>>> + buf += sizeof(val32);
>>>>> + }
>>>>> +}
>>>>> +
>>>>> +int fdt_setprop_reg(void *fdt, int nodeoffset, const char *name,
>>>>> + u64 addr, u64 size)
>>>>> +{
>>>>> + char buf[sizeof(__be32) * 2 * 2];
>>>>> + /* assume dt_root_[addr|size]_cells <= 2 */
>>>>> + void *prop;
>>>>> + size_t buf_size;
>>>>> +
>>>>> + buf_size = of_fdt_reg_cells_size();
>>>>> + prop = buf;
>>>>> +
>>>>> + fill_property(prop, addr, dt_root_addr_cells);
>>>>> + prop += dt_root_addr_cells * sizeof(u32);
>>>>> +
>>>>> + fill_property(prop, size, dt_root_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..9615d6142578 100644
>>>>> --- a/include/linux/of_fdt.h
>>>>> +++ b/include/linux/of_fdt.h
>>>>> @@ -37,8 +37,8 @@ extern void *of_fdt_unflatten_tree(const unsigned long *blob,
>>>>> struct device_node **mynodes);
>>>>>
>>>>> /* TBD: Temporary export of fdt globals - remove when code fully merged */
>>>>> -extern int __initdata dt_root_addr_cells;
>>>>> -extern int __initdata dt_root_size_cells;
>>>>> +extern int dt_root_addr_cells;
>>>>> +extern int dt_root_size_cells;
>>>>> extern void *initial_boot_params;
>>>>>
>>>>> extern char __dtb_start[];
>>>>> @@ -108,5 +108,11 @@ static inline void unflatten_device_tree(void) {}
>>>>> static inline void unflatten_and_copy_device_tree(void) {}
>>>>> #endif /* CONFIG_OF_EARLY_FLATTREE */
>>>>>
>>>>> +bool of_fdt_cells_size_fitted(u64 base, u64 size);
>>>>> +size_t of_fdt_reg_cells_size(void);
>>>>> +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 */
>>>>>
>>>>
>>>>
>>>
>>>
>>
>

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