Messages in this thread | | | Date | Mon, 28 Jun 2021 12:15:51 +0200 | From | Marek Behun <> | Subject | Re: [PATCH v2 18/18] auxdisplay: ht16k33: Add segment display LED support |
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On Mon, 28 Jun 2021 11:21:04 +0200 Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> Hi Marek, > > On Fri, Jun 25, 2021 at 10:39 PM Marek Behun <marek.behun@nic.cz> wrote: > > On Fri, 25 Jun 2021 14:59:02 +0200 > > Geert Uytterhoeven <geert@linux-m68k.org> 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
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