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From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Lukasz Stelmach <l.stelmach@samsung.com>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
	platform-driver-x86@vger.kernel.org,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Subject: Re: [PATCH v8 3/6] software node: implement reference properties
Date: Mon, 9 Nov 2020 21:02:45 +0200
Message-ID: <20201109190245.GL4077@smile.fi.intel.com> (raw)
In-Reply-To: <dleftj4klypf5u.fsf%l.stelmach@samsung.com>

On Mon, Nov 09, 2020 at 07:18:37PM +0100, Lukasz Stelmach wrote:
> It was <2020-11-09 pon 19:24>, when Andy Shevchenko wrote:
> > On Mon, Nov 09, 2020 at 06:02:29PM +0100, Lukasz Stelmach wrote:
> >> It was <2019-11-07 czw 20:22>, when Dmitry Torokhov wrote:

...

> >> I am writing a piece that needs to provide a list of gpios to a
> >> diriver. The above example looks like what I need.
> >
> > Nope.
> >
> > It mustn't be used for GPIOs or PWMs or whatever that either should come via
> > lookup tables or corresponding firmware interface.
> 
> May I ask why? I've read commit descriptions for drivers/base/swnode.c
> and the discussion on lkml and I understand software nodes as a way to
> provide (synthesize) a description for a device that is missing a
> description in the firmware. Another use case seems to be to replace (in
> the long run) platform data. That is what I am trying to use it for.

Yes. Both are correct. They are simply not applicable for everything
(it's not a silver bullet).

> I want my device to be configured with either DT or software_nodes
> created at run time with configfs.

Okay.

> My device is going to use GPIOs
> described in the DT and it is going to be configured via configfs at run
> time.

How is this related to swnodes?
Create GPIO lookup table.

> I could use platform_data to pass structures from configfs but
> software nodes would let me save some code in the device driver and use
> the same paths for both static (DT) and dynamic (configfs)
> configuration.
> 
> Probably I have missed something and I will be greatful, if you tell me
> where I can find more information about software nodes. There are few
> users in the kernel and it isn't obvious for me how to use software
> nodes properly.

gpiod_add_lookup_table().

> >> At the moment the driver gets the list from fwnode/of_node. The list
> >> contain references to phandles which get resolved and and the driver
> >> ends up with a bunch of gpio descriptors. Great.
> >> 
> >> This example looks nice but does the code that reads the reference from
> >> the gpios property and returns a gpiod actually exist? If it doesn't, I
> >> am willing to write it.
> >> 
> >> At first glance it makes more sense to me to pass (struct gpiod_lookup
> >> *) instead of (struct software_node *) and make gpiolib's gpiod_find()
> >> accept lookup tables as parameter instead of searching the
> >> gpio_lookup_list? Or do you think such temporary table should be
> >> assembled from the above structure and then used in gpiod_find()?
> >> 
> >> Any other suggestions on how to get a bunch of gpios (the description
> >> for gpios is available in the devicetree) for a device described with a
> >> software nodes?


-- 
With Best Regards,
Andy Shevchenko



  parent reply index

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08  4:22 [PATCH v8 0/6] software node: add support for " Dmitry Torokhov
2019-11-08  4:22 ` [PATCH v8 1/6] software node: rename is_array to is_inline Dmitry Torokhov
2019-11-08  9:49   ` Rafael J. Wysocki
2019-11-13  6:52   ` Bjørn Mork
2019-11-13  8:08     ` Dmitry Torokhov
     [not found]   ` <CGME20191212111237eucas1p1a278d2d5d2437e3219896367e82604cc@eucas1p1.samsung.com>
2019-12-12 11:12     ` Marek Szyprowski
2019-12-12 11:28       ` Andy Shevchenko
2019-12-12 16:41         ` Rafael J. Wysocki
2019-12-13  6:47           ` Marek Szyprowski
2019-12-13  8:37             ` Rafael J. Wysocki
2019-12-13  1:24       ` Dmitry Torokhov
2019-12-13  6:44         ` Marek Szyprowski
2019-11-08  4:22 ` [PATCH v8 2/6] software node: allow embedding of small arrays into property_entry Dmitry Torokhov
2019-11-08  4:22 ` [PATCH v8 3/6] software node: implement reference properties Dmitry Torokhov
     [not found]   ` <CGME20201109170241eucas1p14c2156334d8c6ef15d52664fa4776f41@eucas1p1.samsung.com>
2020-11-09 17:02     ` Lukasz Stelmach
2020-11-09 17:24       ` Andy Shevchenko
     [not found]         ` <CGME20201109181851eucas1p241de8938e399c0b603c764593b057c41@eucas1p2.samsung.com>
2020-11-09 18:18           ` Lukasz Stelmach
2020-11-09 18:53             ` Dmitry Torokhov
2020-11-09 19:05               ` Andy Shevchenko
2020-11-10 12:39                 ` Heikki Krogerus
2020-11-10 12:46                   ` Rafael J. Wysocki
     [not found]               ` <CGME20201109195504eucas1p19d493c947d8752e39c26202cf0978fc0@eucas1p1.samsung.com>
2020-11-09 19:54                 ` Lukasz Stelmach
2020-11-09 19:02             ` Andy Shevchenko [this message]
     [not found]               ` <CGME20201109194725eucas1p2cc9357486879a14b2ad2f6ef968ff4b2@eucas1p2.samsung.com>
2020-11-09 19:47                 ` Lukasz Stelmach
2020-11-09 21:20                   ` Andy Shevchenko
2019-11-08  4:22 ` [PATCH v8 4/6] platform/x86: intel_cht_int33fe: use inline " Dmitry Torokhov
2019-11-08  4:22 ` [PATCH v8 5/6] software node: remove separate handling of references Dmitry Torokhov
2019-11-08  4:22 ` [PATCH v8 6/6] software node: add basic tests for property entries Dmitry Torokhov

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