On Mon, Nov 09, 2020 at 08:47:14PM +0100, Lukasz Stelmach wrote: > It was <2020-11-09 pon 21:02>, when Andy Shevchenko wrote: > > 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: ... > > 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(). > > > > Yes, that is exactly what my POC code does now. But having a lookup > table together with the rest of the device structures has several > advantages. > > 1) The device may be hotpluggable and there is no > gpiod_remove_lookup_table(). % git grep -n -w gpiod_remove_lookup_table Or I did get it wrong? Did you mean that the removal is not being called? > 2) Having the lookup table allocated and managed together with the rest > of the device seems like a better way to go than on gpio_lookup_list. Nice, what are you going to do with the rest of lookup tables (PWM, regulators, etc)? If you convert, convert them all at least. > 3) As of now I've got a minor issue with device naming. I need to set > dev_id of the table before the device is ready and only after it is > ready, its name is set (in the hotpluggable use case). Hotpluggable devices are very much supported by ACPI assistance. DT I have heard has overlays. What's the issue? > 4) Because no other devices would use this lookup table "publishing" it > rather than keeping together with the device seems at least slightly > odd. > > When the lookup table is attached to the devices and can be passed > around the final lookup can be done with a function like > > static struct gpio_desc *gpiod_find_from_table(struct device *dev, > const char *con_id, unsigned int idx, > unsigned long *flags, struct gpiod_lookup *table) Something sounds fishy about your case. Why do you need to have board code / platform data in the first place? Sorry, but I didn't get why you should reconstruct DT (or ACPI) at run-time without using proper framework / feature (overlays)? > >>>> 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
