[U-Boot] [PATCH] dm: gpio: handle GPIO_ACTIVE_LOW flag in DT

Simon Glass
2016-04-11T14:59:55Z

Hi Eric,

On 11 April 2016 at 08:55, Eric Nelson <eric@nelint.com> wrote:
> Hi Simon,
>
> On 04/11/2016 07:47 AM, Simon Glass wrote:
>> Hi Eric,
>>
>> On 10 April 2016 at 08:48, Eric Nelson <eric@nelint.com> wrote:
>>> Hi Simon,
>>>
>>> On 04/09/2016 11:33 AM, Simon Glass wrote:
>>>> On 4 April 2016 at 11:50, Stephen Warren <swarren@wwwdotorg.org> wrote:
>>>>> On 04/03/2016 08:07 AM, Eric Nelson wrote:
>>>>>> On 04/02/2016 08:37 PM, Stephen Warren wrote:
>>>>>>> On 04/02/2016 09:13 AM, Eric Nelson wrote:
>>>>>>>> On 04/01/2016 10:46 PM, Peng Fan wrote:
>>>>>>>>> On Thu, Mar 31, 2016 at 01:41:04PM -0700, Eric Nelson wrote:
>>>>>>>>>> On 03/28/2016 09:57 PM, Peng Fan wrote:
>>>>>>>>>>> On Fri, Mar 25, 2016 at 01:12:11PM -0700, Eric Nelson wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> Device tree parsing of GPIO nodes is currently ignoring flags.
>>>>>>>>>>>>
>>>>>>>>>>>> Add support for GPIO_ACTIVE_LOW by checking for the presence
>>>>>>>>>>>> of the flag and setting the desc->flags field to the driver
>>>>>>>>>>>> model constant GPIOD_ACTIVE_LOW.
>>>>>>>>>>>
>>>
>>> <snip>
>>>
>>>>>
>>>>> The intent of the change is good.
>>>>>
>>>>> I'm not sure why we need to remove gpio_find_and_xlate(); it provides an API
>>>>> for clients so they don't need to know how to access driver functionality
>>>>> through the ops pointer, which I think is an internal/private implementation
>>>>> detail. Is that detail exposed to clients in other places? If so, removing
>>>>> the wrapper seems fine. If not, I suspect it's a deliberate abstraction.
>>>>
>>>> This seems a bit pedantic, but since Linux does it this way I think we
>>>> should follow along.
>>>>
>>>> Eric you still get to remove the code from all the GPIO drivers - the
>>>> difference is just creating a common function to call when no xlate()
>>>> method is available.
>>>>
>>>> Can you please take a look at what Stephen suggests?
>>>>
>>>
>>> Got it. I'm just not sure about where to start (before or after
>>> the patch set you sent) and whether to also remove offset parsing
>>> from gpio_find_and_xlate().
>>>
>>
>> Which patch did I send? My understanding is:
>>
>
> At the time I sent this, you had just submitted the patch set adding
> more driver-model support for block devices.
>
> http://lists.denx.de/pipermail/u-boot/2016-April/251095.html
>
>> - Add my review/ack tag to the patches as necessary
>> - Drop the tegra patch
>> - Update gpio_find_and_xlate() to call a default function if there is
>> no xlate() method
>> - Resend the series
>>
>> I'm not sure about removing the existing functionality from
>> gpio_find_and_xlate(), but my guess is that it is best to move it to
>> your default function, so that gpio_find_and_xlate() doesn't include
>> any default behaviour in the case where there is a xlate() method.
>>
>
> Reviewing the use of the offset field did yield some information about
> the broken sunxi support and also that Vybrid was also missing
> the xlate routine.
>
> Since reviewing your patch sets (driver model updates for blk and also
> driver model updates for mmc) will take some time, so I'll base an
> updated patch set on master. My guess is that any merge issues will
> be trivial.

Yes, that's right.
>
> I'll remove your acks in the updated patch set, since the updates
> to the drivers won't drop the xlate field, but will connect them
> to the common (__maybe_unused) routine. This will prevent the code
> from leaking into machines like Tegra that don't need the common code.

I'm pretty sure you can drop the xlate() implementations from the
functions, though, and those at the patches I acked.

I don't think you need __maybe_unused

static int gpio_find_and_xlate(...)
{
get ops...

if (ops->xlate)
return ops->xlate(....)
else
return gpio_default_xlate()...
}

gpio_default_xlate() (or whatever name you use) should be exported so
drivers can use it.

Regards,
Simon