diff mbox series

[v1] Documentation: ACPI: explain how to use gpio-line-names

Message ID 20201111130435.432982-1-f.suligoi@asem.it
State New
Headers show
Series [v1] Documentation: ACPI: explain how to use gpio-line-names | expand

Commit Message

Flavio Suligoi Nov. 11, 2020, 1:04 p.m. UTC 
The "gpio-line-names" declaration is not fully
documented, so can be useful to add some important
information and one more example.

This commit also fix a trivial syntax error.

Signed-off-by: Flavio Suligoi <f.suligoi@asem.it>
---
 .../firmware-guide/acpi/gpio-properties.rst   | 58 ++++++++++++++++++-
 1 file changed, 56 insertions(+), 2 deletions(-)

Comments

Andy Shevchenko Nov. 11, 2020, 2:57 p.m. UTC | #1 
On Wed, Nov 11, 2020 at 4:53 PM Flavio Suligoi <f.suligoi@asem.it> wrote:

...

> > Since it's rest, I would expect gpio-line-names in above paragraphs to

> > be a term, something like

> > ``gpio-line-names`` (double back quotes on each side). Yes, I know

> > that there are other places which need to be amended, but I believe

> > it's out of scope of this patch.

>

> Ok, I'll use the backquotes for code samples, right!

> If you want, when this patch will be concluded, I can check all the ACPI

> documentation to put all code samples into backquotes.


I'm not sure I understand what you meant under 'code samples'. The
code excerpts like below are fine, what I'm talking about is the
reference to properties in the text.

...

> > ``""`` but better to check the resulting (rendered) file. You may use

> > rst2pdf script for that.

>

> OK for the``""``.

> I check the rendered HTML using the usual "make htmldocs". Is it enough?


Ideally it's not enough. html, pdf and man all should be checked.

-- 
With Best Regards,
Andy Shevchenko
diff mbox series

Patch

diff --git a/Documentation/firmware-guide/acpi/gpio-properties.rst b/Documentation/firmware-guide/acpi/gpio-properties.rst
index bb6d74f23ee0..a9f4dfa932cc 100644
--- a/Documentation/firmware-guide/acpi/gpio-properties.rst
+++ b/Documentation/firmware-guide/acpi/gpio-properties.rst
@@ -107,7 +107,61 @@  Example::
 
 - gpio-line-names
 
-Example::
+The "gpio-line-names" declaration is a list of strings ("names"), which
+describes each line/pin of a GPIO controller/expander.
+This list, contained in a package, must be inserted inside the GPIO controller
+declaration of an ACPI table (typically inside the DSDT).
+The gpio-line-names list must respect the following rules (see also the
+examples):
+
+  - the first name in the list corresponds with the first line/pin of the GPIO
+    controller/expander
+  - the names inside the list must be consecutive (no "holes" are permitted)
+  - the list can be incomplete and can end before the last GPIO line: in
+    other words, it is not mandatory to fill all the GPIO lines
+  - empty names are allowed (two quotation marks "" correspond to an empty name)
+
+Example of a GPIO controller of 16 lines, with an incomplete list with two
+empty names::
+
+  Package () {
+      "gpio-line-names",
+      Package () {
+          "pin_0",
+          "pin_1",
+          "",
+          "",
+          "pin_3",
+          "pin_4_push_button"
+      }
+  }
+
+At runtime, the above declaration produces the following result (using the
+"libgpiod" tools)::
+
+  root@debian:~# gpioinfo gpiochip4
+  gpiochip4 - 16 lines:
+          line   0:      "pin_0"       unused   input  active-high
+          line   1:      "pin_1"       unused   input  active-high
+          line   2:      unnamed       unused   input  active-high
+          line   3:      unnamed       unused   input  active-high
+          line   4:      "pin_3"       unused   input  active-high
+          line   5: "pin_4_push_button" unused input active-high
+          line   6:      unnamed       unused   input  active-high
+          line   7       unnamed       unused   input  active-high
+          line   8:      unnamed       unused   input  active-high
+          line   9:      unnamed       unused   input  active-high
+          line  10:      unnamed       unused   input  active-high
+          line  11:      unnamed       unused   input  active-high
+          line  12:      unnamed       unused   input  active-high
+          line  13:      unnamed       unused   input  active-high
+          line  14:      unnamed       unused   input  active-high
+          line  15:      unnamed       unused   input  active-high
+  root@debian:~# gpiofind pin_4_push_button
+  gpiochip4 5
+  root@debian:~#
+
+Another example::
 
   Package () {
       "gpio-line-names",
@@ -191,7 +245,7 @@  The driver might expect to get the right GPIO when it does::
 but since there is no way to know the mapping between "reset" and
 the GpioIo() in _CRS desc will hold ERR_PTR(-ENOENT).
 
-The driver author can solve this by passing the mapping explictly
+The driver author can solve this by passing the mapping explicitly
 (the recommended way and documented in the above chapter).
 
 The ACPI GPIO mapping tables should not contaminate drivers that are not