From: Bartosz Golaszewski <brgl@bgdev.pl>
To: Linus Walleij <linus.walleij@linaro.org>,
Jonathan Corbet <corbet@lwn.net>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Kent Gibson <warthog618@gmail.com>
Cc: linux-gpio@vger.kernel.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org,
Bartosz Golaszewski <bgolaszewski@baylibre.com>
Subject: [PATCH 2/9] Documentation: gpio: add documentation for gpio-mockup
Date: Thu, 24 Sep 2020 13:38:35 +0200 [thread overview]
Message-ID: <20200924113842.11670-3-brgl@bgdev.pl> (raw)
In-Reply-To: <20200924113842.11670-1-brgl@bgdev.pl>
From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
There's some documentation for gpio-mockup's debugfs interface in the
driver's source but it's not much. Add proper documentation for this
testing module.
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
.../admin-guide/gpio/gpio-mockup.rst | 50 +++++++++++++++++++
1 file changed, 50 insertions(+)
create mode 100644 Documentation/admin-guide/gpio/gpio-mockup.rst
diff --git a/Documentation/admin-guide/gpio/gpio-mockup.rst b/Documentation/admin-guide/gpio/gpio-mockup.rst
new file mode 100644
index 000000000000..9fa1618b3adc
--- /dev/null
+++ b/Documentation/admin-guide/gpio/gpio-mockup.rst
@@ -0,0 +1,50 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+GPIO Testing Driver
+===================
+
+The GPIO Testing Driver (gpio-mockup) provides a way to create simulated GPIO
+chips for testing purposes. The lines exposed by these chips can be accessed
+using the standard GPIO character device interface as well as manipulated
+using the dedicated debugfs directory structure.
+
+Creating simulated chips using module params
+--------------------------------------------
+
+When loading the gpio-mockup driver a number of parameters can be passed to the
+module.
+
+ gpio_mockup_ranges
+
+ This parameter takes an argument in the form of an array of integer
+ pairs. Each pair defines the base GPIO number (if any) and the number
+ of lines exposed by the chip. If the base GPIO is -1, the gpiolib
+ will assign it automatically.
+
+ Example: gpio_mockup_ranges=-1,8,-1,16,405,4
+
+ The line above creates three chips. The first one will expose 8 lines,
+ the second 16 and the third 4. The base GPIO for the third chip is set
+ to 405 while for two first chips it will be assigned automatically.
+
+ gpio_named_lines
+
+ This parameter doesn't take any arguments. It lets the driver know that
+ GPIO lines exposed by it should be named.
+
+ The name format is: gpio-mockup-X-Y where X is mockup chip's ID
+ and Y is the line offset.
+
+Manipulating simulated lines
+----------------------------
+
+Each mockup chip creates its own subdirectory in /sys/kernel/debug/gpio-mockup/.
+The directory is named after the chip's label. A symlink is also created, named
+after the chip's name, which points to the label directory.
+
+Inside each subdirectory, there's a separate attribute for each GPIO line. The
+name of the attribute represents the line's offset in the chip.
+
+Reading from a line attribute returns the current value. Writing to it (0 or 1)
+changes the configuration of the simulated pull-up/pull-down resistor
+(1 - pull-up, 0 - pull-down).
--
2.26.1
next prev parent reply other threads:[~2020-09-24 11:39 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-24 11:38 [PATCH 0/9] gpio: mockup: refactoring + documentation Bartosz Golaszewski
2020-09-24 11:38 ` [PATCH 1/9] lib: string_helpers: provide kfree_strarray() Bartosz Golaszewski
2020-09-25 8:48 ` Andy Shevchenko
2020-09-25 11:32 ` Bartosz Golaszewski
2020-09-25 12:28 ` Andy Shevchenko
2020-09-24 11:38 ` Bartosz Golaszewski [this message]
2020-09-24 11:38 ` [PATCH 3/9] gpio: mockup: drop unneeded includes Bartosz Golaszewski
2020-09-24 11:38 ` [PATCH 4/9] gpio: mockup: use KBUILD_MODNAME Bartosz Golaszewski
2020-09-24 11:38 ` [PATCH 5/9] gpio: mockup: use pr_fmt() Bartosz Golaszewski
2020-09-24 16:04 ` Joe Perches
2020-09-24 11:38 ` [PATCH 6/9] gpio: mockup: remove unneeded return statement Bartosz Golaszewski
2020-09-24 11:38 ` [PATCH 7/9] gpio: mockup: pass the chip label as device property Bartosz Golaszewski
2020-09-25 9:00 ` Andy Shevchenko
2020-09-24 11:38 ` [PATCH 8/9] gpio: mockup: use the generic 'gpio-line-names' property Bartosz Golaszewski
2020-09-25 9:03 ` Andy Shevchenko
2020-09-25 11:40 ` Bartosz Golaszewski
2020-09-25 12:30 ` Andy Shevchenko
2020-09-28 8:44 ` Bartosz Golaszewski
2020-09-28 9:11 ` Andy Shevchenko
2020-09-28 9:58 ` Bartosz Golaszewski
2020-09-24 11:38 ` [PATCH 9/9] gpio: mockup: refactor the module init function Bartosz Golaszewski
2020-09-25 9:04 ` [PATCH 0/9] gpio: mockup: refactoring + documentation Andy Shevchenko
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200924113842.11670-3-brgl@bgdev.pl \
--to=brgl@bgdev.pl \
--cc=andriy.shevchenko@linux.intel.com \
--cc=bgolaszewski@baylibre.com \
--cc=corbet@lwn.net \
--cc=linus.walleij@linaro.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-gpio@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=warthog618@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).