On Mon, 28 Jun 2021 11:21:04 +0200
Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> Hi Marek,
>
> On Fri, Jun 25, 2021 at 10:39 PM Marek Behun <marek.behun@xxxxxx> wrote:
> > On Fri, 25 Jun 2021 14:59:02 +0200
> > Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> >
> > > Instantiate a single LED for a segment display. This allows the user to
> > > control display brightness and blinking through the LED class API and
> > > triggers, and exposes the display color.
> > > The LED will be named "auxdisplay:<color>:backlight".
> >
> > What if there are multiple "auxdisplay"s ?
>
> I understand the LED core will just add a suffix on a name collision.
>
> > Doesn't this subsystem have IDs? So that you can use auxdisplayN for
> > device name, for example?
>
> Auxdisplay does not have IDs, as there is no subsystem to register
> with. It's just a collection of drivers for auxiliary displays with
> no common API. Some drivers use fbdev, others use a chardev, or an
> attribute file in sysfs.
>
> BTW, I just followed Pavel's advice in naming.
Very well.
> > > + of_property_read_u32(node, "color", &color);
> > > + seg->led.name = devm_kasprintf(dev, GFP_KERNEL,
> > > + "auxdisplay:%s:" LED_FUNCTION_BACKLIGHT,
> > > + color < LED_COLOR_ID_MAX ? led_colors[color] : "");
> >
> > If you use devm_led_classdev_register_ext and pass struct
> > led_init_data, LED core will generate name of the LED itself.
>
> Will that make any difference, except for adding more code?
You are hardcoding the backlight function. Using the _ext() registering
function will make it so that the function and color are parsed from
fwnode by LED core. I understand that the function will always be
"backlight" in this case, but this should be specified in the
device-tree anyway, so why not use it?
> Looking at the implementation, I still have to use devm_kasprintf()
> to combine color and function for led_init_data.default_label?
AFAIK you don't have to fill in default_label. (If the needed OF
properties are not present so that default_label is tried, it means the
device-tree does not correctly specify the device. In that case I don't
think it is a problem if the default_label is not present and LED
core will use the OF node name as the LED name.)
The code could look like this
struct led_init_data init_data = {};
init_data.fwnode = of_fwnode_handle(node);
init_data.devicename = "auxdisplay";
init_data.devname_mandatory = true;
...register_ext();
But if you still don't want to do this then ignore me :)
Marek
