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

[Simon Glass]

Hi Marek,

On 7 June 2017 at 06:55, Marek Vasut <marex at denx.de> wrote:
> On 06/07/2017 02:53 PM, Simon Glass wrote:
>> Hi Marek,
>>
>> On 7 June 2017 at 06:41, Marek Vasut <marex at denx.de> wrote:
>>> On 06/07/2017 02:38 PM, Simon Glass wrote:
>>>> +Tom for comment
>>>>
>>>> Hi Marek,
>>>>
>>>> On 7 June 2017 at 00:27, Marek Vasut <marex at denx.de> wrote:
>>>>> On 06/07/2017 02:16 AM, Simon Glass wrote:
>>>>>> 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.
>>>>>
>>>>> I was under the impression that u-boot by convention uses uintptr_t 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!)
>>>>>
>>>>> Then I guess half of the codebase is inconsistent.
>>>>
>>>> Actually about 10%:
>>>>
>>>> git grep uintptr_t |wc -l
>>>> 395
>>>> git grep ulong |wc -l
>>>> 4024
>>>
>>> I don't think this is a valid way to count it at all, since uintptr_t is
>>> only used for casting pointer to number, while ulong is used for
>>> arbitrary numbers.
>>>
>>>> Clearly we use ulong all over the place for addresses - see image.c,
>>>> most commands, etc.
>>>
>>> But none of those use ulong as device address pointers .
>>
>> Is there a distinction between a device address pointer and some other
>> type of address?
>
> ulong is not used only for addresses, which your metric doesn't account for.

OK, but if you look around you can see my point. See for example
cmd/mem.c which uses ulong everywhere. Image handling is the same -
see e.g. image.h struct image_info and struct bootm_headers. Are you
saying those are wrong, or that this case is different, or something
else?

Regards,
Simon