Re: [RFCv4 06/11] misc: Introduce Nokia CMT driver

[Linus Walleij]

On Mon, Dec 16, 2013 at 1:15 PM, Sebastian Reichel <sre@xxxxxxxxxx> wrote:
> On Mon, Dec 16, 2013 at 10:48:06AM +0100, Linus Walleij wrote:

>> I.e. it doesn't look device-specific at all, just like some
>> generic glue code that could be useful to many such
>> scenarios.
>
> I like the idea.
>
> Probably the remaining gpio exporting code can be converted into
> some generic gpio-sysfs-export driver as well.

I am very reluctant in letting device trees specify exports of GPIOs
to userspace, not so much because it's Linux-specific but for
the fact that people are doing things in userspace that should not
be done in userspace.

Last time it was proposed I asked to the specific usecase,
exactly why userspace needed this handle on a physical
GPIO line, and why it can't use another userspace interface
(example: leds, keys etc.)

> What do you think about the following?
>
> /*
>  * driver, which provides generic reset notifications
>  */
> cmt_reset: reset-notifier {
>     compatible = "linux,reset-notification";
>
>     interrupts = <gpio>;
> };

Looks good to me.

> /*
>  * driver, which exports the specified gpios in sysfs with the
>  * supplied names. The device will be named according to the
>  * label
>  */
> cmt_gpios: gpio-sysfs-export {
>     compatible = "linux,gpio-sysfs-export";
>     label = "nokia-cmt";
>
>     gpios = <A>, <B>, ...;
>     gpio-names = "A", "B", ...;
> };

Please follow the discussion on this topic:
http://marc.info/?l=linux-gpio&m=138201170431416&w=2

>> Why are you using a tasklet rather than a work
>> for this?
>
> No particular reason. I just took this over from Nokia's code.

Can you try to use a work instead?

Yours,
Linus Walleij
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