Messages in this thread | | | Date | Wed, 18 Sep 2019 15:32:14 -0700 | From | rananta@codeauro ... | Subject | Re: [PATCH] of: Add of_get_memory_prop() |
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On 2019-09-18 13:13, Rob Herring wrote: > On Wed, Sep 18, 2019 at 1:47 PM Raghavendra Rao Ananta > <rananta@codeaurora.org> wrote: >> >> On some embedded systems, the '/memory' dt-property gets updated >> by the bootloader (for example, the DDR configuration) and then >> gets passed onto the kernel. The device drivers may have to read >> the properties at runtime to make decisions. Hence, add >> of_get_memory_prop() for the device drivers to query the requested > > Function name doesn't match. Device drivers don't need to access the > FDT. > >> properties. >> >> Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org> >> --- >> drivers/of/fdt.c | 27 +++++++++++++++++++++++++++ >> include/linux/of_fdt.h | 1 + >> 2 files changed, 28 insertions(+) > > We don't add kernel api's without users. > >> >> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c >> index 223d617ecfe1..925cf2852433 100644 >> --- a/drivers/of/fdt.c >> +++ b/drivers/of/fdt.c >> @@ -79,6 +79,33 @@ void __init of_fdt_limit_memory(int limit) >> } >> } >> >> +/** >> + * of_fdt_get_memory_prop - Return the requested property from the >> /memory node >> + * >> + * On match, returns a non-zero positive value which represents the >> property >> + * value. Otherwise returns -ENOENT. >> + */ >> +int of_fdt_get_memory_prop(const char *pname) >> +{ >> + int memory; >> + int len; >> + fdt32_t *prop = NULL; >> + >> + if (!pname) >> + return -EINVAL; >> + >> + memory = fdt_path_offset(initial_boot_params, "/memory"); > > Memory nodes should have a unit-address, so this won't work frequently. Sorry, can you please elaborate more on this? What do you mean by unit-address and working frequently? > >> + if (memory > 0) >> + prop = fdt_getprop_w(initial_boot_params, memory, >> + pname, &len); >> + >> + if (!prop || len != sizeof(u32)) >> + return -ENOENT; >> + >> + return fdt32_to_cpu(*prop); >> +} >> +EXPORT_SYMBOL_GPL(of_fdt_get_memory_prop); >> + >> static bool of_fdt_device_is_available(const void *blob, unsigned >> long node) >> { >> const char *status = fdt_getprop(blob, node, "status", NULL); >> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h >> index acf820e88952..537f29373358 100644 >> --- a/include/linux/of_fdt.h >> +++ b/include/linux/of_fdt.h >> @@ -38,6 +38,7 @@ extern char __dtb_end[]; >> /* Other Prototypes */ >> extern u64 of_flat_dt_translate_address(unsigned long node); >> extern void of_fdt_limit_memory(int limit); >> +extern int of_fdt_get_memory_prop(const char *pname); >> #endif /* CONFIG_OF_FLATTREE */ >> >> #ifdef CONFIG_OF_EARLY_FLATTREE >> -- >> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora >> Forum, >> a Linux Foundation Collaborative Project >> - Raghavendra
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