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

[Simon Glass]

Hi,

On 6 June 2017 at 17:59, Dr. Philipp Tomsich
<philipp.tomsich at theobroma-systems.com> wrote:
> 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.

I don't know of any deep reason except that long is defined to be able
to hold an address, and ulong makes sense since an address is
generally considered unsigned.

U-Boot by convention uses ulong for addresses. You can see this all
around the code base so I am really just arguing in favour of
consistency (and I suppose ulong is easier to type!)

Regards,
Simon