[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 07:33, Marek Vasut <marex at denx.de> wrote:
> On 06/07/2017 03:28 PM, Simon Glass wrote:
>> 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?
>
> I guess we could convert them to uintptr_t , but I've mostly used
> uintptr_t when converting void __iomem * to numbers written to HW
> registers .
>
> I also think being explicit about "hey, this is a pointer converted to a
> number" does not hurt, so I like the uintptr_t better than ulong for
> such converted pointers.
>
> re cmd/mem.c , it's legacy code , the new code and/or code which used to
> trigger compiler warnings on ie. arm64 was fixed up mostly to use the
> uintptr_t recently.

OK, how about updating https://www.denx.de/wiki/U-Boot/CodingStyle
with what we now want?

Regards,
Simon