[U-Boot] [PATCH v2 4/7] usb: dwc2-otg: make regs_otg (in platdata) a uintptr_t

[Dr. Philipp Tomsich]

Simon,

> On 06 Jun 2017, at 23:09, Simon Glass <sjg at chromium.org> wrote:
> 
> Hi Philipp,
> 
> On 6 June 2017 at 07:42, Philipp Tomsich
> <philipp.tomsich at theobroma-systems.com> wrote:
>> The regs_otg field in uintptr_t of the platform data structure for
>> dwc2-otg has thus far been an unsigned int, but will eventually be
>> casted into a void*.
>> 
>> This raises the following error with GCC 6.3 and buildman:
>>  ../drivers/usb/gadget/dwc2_udc_otg.c: In function 'dwc2_udc_probe':
>>  ../drivers/usb/gadget/dwc2_udc_otg.c:821:8: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
>>    reg = (struct dwc2_usbotg_reg *)pdata->regs_otg;
>>          ^
>> 
>> This changes regs_otg to a uintptr_t to ensure that it is large enough
>> to hold any valid pointer (and fix the associated warning).
>> 
>> Signed-off-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
>> 
>> ---
>> 
>> Changes in v2:
>> - (new patch) fix a int-to-pointer cast warning for regs_otg in
>>  dwc2-otg to fix a buildman failure for u-boot-rockchip/master at 2b19b2f
>> 
>> include/usb/dwc2_udc.h | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>> 
>> diff --git a/include/usb/dwc2_udc.h b/include/usb/dwc2_udc.h
>> index 7324d8a..1a370e0 100644
>> --- a/include/usb/dwc2_udc.h
>> +++ b/include/usb/dwc2_udc.h
>> @@ -16,7 +16,7 @@ struct dwc2_plat_otg_data {
>>        int             phy_of_node;
>>        int             (*phy_control)(int on);
>>        unsigned int    regs_phy;
>> -       unsigned int    regs_otg;
>> +       uintptr_t       regs_otg;
> 
> Can you use ulong instead?

Sure, but can I first ask “why?”.
I may reopen an old discussion with this… if so, forgive my ignorance:

uintptr_t makes the most sense for this use case in the C99 (or later) type system,
as we want this field to hold an integer (i.e. the address from the physical memory
map for one of the register blocks) that will be casted into a pointer. 
The uintptr_t type will always the matching size in any and all programming models;
in contrast, ulong would be wrong for LLP64 (and LLP64 probably “doesn’t matter”
in the context of U-Boot anyway).

What I always found odd, was that uintptr_t is optional according to ISO9899.
I would thus not have been surprised if there’s a concern for portability between
compilers behind this, but then again … U-Boot makes extensive use of GCC
extensions (such as inline assembly).

So I am apparently missing something here.

Cheers,
Philipp.