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
