Messages in this thread | | | Date | Tue, 30 Jul 2019 14:30:33 +0300 | From | Heikki Krogerus <> | Subject | Re: [PATCH 2/2] gpiolib: add support for fetching descriptors from static properties |
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Hi Dmitry,
On Sat, Jul 13, 2019 at 12:52:59AM -0700, Dmitry Torokhov wrote: > Now that static device properties understand notion of child nodes, let's > teach gpiolib to tie such children and machine GPIO descriptor tables. > We will continue using a single table for entire device, but instead of > using connection ID as a lookup key in the GPIO descriptor table directly, > we will perform additional translation: fwnode_get_named_gpiod() when > dealing with property_set-backed fwnodes will try parsing string property > with name matching connection ID and use result of the lookup as the key in > the table: > > static const struct property_entry dev_child1_props[] __initconst = { > ... > PROPERTY_ENTRY_STRING("gpios", "child-1-gpios"), > { } > }; > > static struct gpiod_lookup_table dev_gpiod_table = { > .dev_id = "some-device", > .table = { > ... > GPIO_LOOKUP_IDX("B", 1, "child-1-gpios", 1, GPIO_ACTIVE_LOW), > ... > }, > };
We don't need struct gpiod_lookup_table anymore. We can mimic DT with the software nodes now that we have those "reference properties". A gpio reference with the software nodes would look something like this:
enum { GPIO_CONTROLLER, MY_DEVICE };
static const struct software_node nodes[];
static const struct software_node_ref_args reset_gpio_ref = { .node = &nodes[GPIO_CONTROLLER], .nargs = 2, .args = { 14, /* line number */ GPIO_ACTIVE_HIGH /* flags */ } };
static const struct software_node_reference my_refs[] = { { "reset-gpios", 1, &reset_gpio_ref } };
/* Optionally, we could support gpiochip finding by name... */ static const struct property_entry my_props[] = { PROPERTY_ENTRY_STRING("gpio-controller", "name_of_the_controller") };
static const struct software_node nodes[] = { [GPIO_CONTROLLER] = { "gpio_controller" }, [MY_DEVICE] = { "my_device", NULL, my_props, my_refs } };
void my_init(void) { ... ret = software_node_register_nodes(nodes); ... }
In gpiolib we should now be able to access that reference with fwnode_property_get_references_args():
static int gpiochip_match_fwnode(struct gpio_chip *chip, void *fwnode) { /* The fwnode member needs to be added to struct gpio_chip */ return chip->fwnode == fwnode; }
static struct gpio_desc *gpiod_find(struct device *dev, const char *con_id, unsigned int idx, unsigned long flags) { struct fwnode_reference_args args; struct gpio_chip *chip; struct gpio_desc *desc; const char *name; int ret;
ret = fwnode_property_get_refernce_args(dev_fwnode(dev), con_id, NULL, idx, &args); ...
/* Let's find the gpiochip */ chip = gpiochip_find(args.fwnode, gpiochip_match_fwnode); ...
/* Or optionally with find_chip_by_name() */ //ret = device_property_read_string(dev, "gpio-controller", &name); ... //chip = find_chip_by_name(name); ...
/* I'm assuming hwnum is the same as line number? */ desc = gpiochip_get_desc(chip, args.args[0]); *flags = args.args[1];
return desc; }
The above is just an example, but I'm pretty sure that something like it (with a little bit of tuning) is all that we need.
thanks,
-- heikki
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