linux-kernel - Re: [PATCH v8 3/6] software node: implement reference properties

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Date:   Mon, 9 Nov 2020 19:24:35 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Lukasz Stelmach <l.stelmach@...sung.com>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH v8 3/6] software node: implement reference properties

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:
> > It is possible to store references to software nodes in the same fashion as
> > other static properties, so that users do not need to define separate
> > structures:
> >
> > static const struct software_node gpio_bank_b_node = {
> > 	.name = "B",
> > };
> >
> > static const struct property_entry simone_key_enter_props[] = {
> > 	PROPERTY_ENTRY_U32("linux,code", KEY_ENTER),
> > 	PROPERTY_ENTRY_STRING("label", "enter"),
> > 	PROPERTY_ENTRY_REF("gpios", &gpio_bank_b_node, 123, GPIO_ACTIVE_LOW),
> > 	{ }
> > };
> >
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > ---
> 
> 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.

> 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