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

From: AKASHI Takahiro
Date: Wed Sep 26 2018 - 01:56:04 EST

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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.
>
> 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
>
>
> >
> >
> >> 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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