property, and a #gpio-cells integer property, which indicates the number of
cells in a gpio-specifier.
+Some system-on-chips (SoCs) use the concept of GPIO banks. A GPIO bank is an
+instance of a hardware IP core on a silicon die, usually exposed to the
+programmer as a coherent range of I/O addresses. Usually each such bank is
+exposed in the device tree as an individual gpio-controller node, reflecting
+the fact that the hardware was synthesized by reusing the same IP block a
+few times over.
+
Optionally, a GPIO controller may have a "ngpios" property. This property
indicates the number of in-use slots of available slots for GPIOs. The
typical example is something like this: the hardware register is 32 bits
and which are dummies. The bindings for this case has not yet been
specified, but should be specified if/when such hardware appears.
+Optionally, a GPIO controller may have a "gpio-line-names" property. This is
+an array of strings defining the names of the GPIO lines going out of the
+GPIO controller. This name should be the most meaningful producer name
+for the system, such as a rail name indicating the usage. Package names
+such as pin name are discouraged: such lines have opaque names (since they
+are by definition generic purpose) and such names are usually not very
+helpful. For example "MMC-CD", "Red LED Vdd" and "ethernet reset" are
+reasonable line names as they describe what the line is used for. "GPIO0"
+is not a good name to give to a GPIO line. Placeholders are discouraged:
+rather use the "" (blank string) if the use of the GPIO line is undefined
+in your design. The names are assigned starting from line offset 0 from
+left to right from the passed array. An incomplete array (where the number
+of passed named are less than ngpios) will still be used up until the last
+provided valid line index.
+
Example:
gpio-controller@00000000 {
gpio-controller;
#gpio-cells = <2>;
ngpios = <18>;
+ gpio-line-names = "MMC-CD", "MMC-WP", "VDD eth", "RST eth", "LED R",
+ "LED G", "LED B", "Col A", "Col B", "Col C", "Col D",
+ "Row A", "Row B", "Row C", "Row D", "NMI button",
+ "poweroff", "reset";
}
The GPIO chip may contain GPIO hog definitions. GPIO hogging is a mechanism