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

[AKASHI Takahiro]

Frank,

Thank you for the comments. I will address all of them, but
have one question:

On Fri, Sep 07, 2018 at 12:53:58PM -0700, 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 */
> > +
> 
> 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()
> 
> 
> > +{
> > +	/* 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.

What is the upper limit here?
For instance, #address_cells = <1> and #size_cells = <1>,
and can 'base + size' be over U32_MAX?
Assuming 'not' is quite reasonable, but it seems to me
that devicetree spec doesn't exclude it, as least I couldn't
find any notes about such a case.
(In my understands, #address_cells only restricts a size in 'reg' property.)

Thanks,
-Takahiro Akashi

> 
> > +
> > +	return true;
> > +}
> > +
> > +size_t of_fdt_reg_cells_size(void)
> 
> Please rename as of_fdt_root_range_size()
> 
> 
> > +{
> > +	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 */
> > 
>