lkml.org 
[lkml]   [2015]   [Feb]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [RFC PATCH] gpio: support for GPIO forwarding
On Fri, Jan 23, 2015 at 8:21 PM, Heikki Krogerus
<heikki.krogerus@linux.intel.com> wrote:
> Hi guys,
>
> On Thu, Jan 22, 2015 at 05:14:22PM +0100, Rafael J. Wysocki wrote:
>> On Thursday, January 22, 2015 11:57:55 AM Alexandre Courbot wrote:
>> > If we decide to go ahead with the solution proposed by this patch for
>> > practical reasons (which are good reasons indeed), I still have one
>> > problem with its current form.
>> >
>> > As the discussion highlighted, this is an ACPI problem, so I'd very
>> > much like it to be confined to the ACPI GPIO code, to be enabled only
>> > when ACPI is, and to use function names that start with acpi_gpio.
>>
>> I can agree with that.
>>
>> > The current implementation leverages platform lookup, making said lookup
>> > less efficient in the process and bringing confusion about its
>> > purpose. Although the two processes are indeed similar, they are
>> > separate things: one is a legitimate way to map GPIOs, the other is a
>> > fixup for broken firmware.
>> >
>> > I suppose we all agree this is a hackish fix, so let's confine it as
>> > much as we can.
>>
>> OK
>>
>> Heikki, any comments?
>
> I'm fine with that.
>
> That actually makes me think that we could then drop the lookup tables
> completely and use device properties instead with the help of "generic
> property" (attached):
>
> We would just need to agree on the format how to describe a gpio
> property, document it and of course convert the current users as
> usual. The format could be something like this as an example (I'm
> writing this out of my head so don't shoot me if you can see it would
> not work. Just an example):
>
> static const u32 example_gpio[] = { <gpio>, <flags>,爙;
>
> static struct dev_gen_prop example_prop[] =
> {
> .type = DEV_PROP_U32,
> .name = "gpio,<con_id>",
> .nval = 2,
> .num = &example_gpio,
> },
> { },
> };
>
> static struct platform_device example_pdev = {
> ...
> .dev = {
> .gen_prop = &example_prop,
> },
> }
>
>
> In gpiolib.c we would then, instead of going through the lookups,
> simply ask for that property:
>
> ...
> sprintf(propname, "gpio,%s", con_id);
> device_property_read_u32_array(dev, propname, &val, 2);
> ...
> desc = gpio_to_desc(val[0]);
> flags = val[1];
> ...
>
>
> So this is just and idea. I think it would be relatively easy to
> implement. What do you guys think?

At first sight, that looks like a very good idea and a great use of
the device properties API. Are you willing to explore it further?


\
 
 \ /
  Last update: 2015-02-10 10:41    [W:1.076 / U:0.020 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site