On Tue, Mar 09, 2021 at 09:59:18PM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski
>
> Implement a new, modern GPIO testing module controlled by configfs
> attributes instead of module parameters. The goal of this driver is
> to provide a replacement for gpio-mockup that will be easily extensible
> with new features and doesn't require reloading the module to change
> the setup.
Thanks for an update!
Looks much better now, although few minor comments below.
Reviewed-by: Andy Shevchenko
>
> Signed-off-by: Bartosz Golaszewski
> ---
> Documentation/admin-guide/gpio/gpio-sim.rst | 72 ++
> drivers/gpio/Kconfig| 8 +
> drivers/gpio/Makefile | 1 +
> drivers/gpio/gpio-sim.c | 879
> 4 files changed, 960 insertions(+)
> create mode 100644 Documentation/admin-guide/gpio/gpio-sim.rst
> create mode 100644 drivers/gpio/gpio-sim.c
>
> diff --git a/Documentation/admin-guide/gpio/gpio-sim.rst
> b/Documentation/admin-guide/gpio/gpio-sim.rst
> new file mode 100644
> index ..08eac487e35e
> --- /dev/null
> +++ b/Documentation/admin-guide/gpio/gpio-sim.rst
> @@ -0,0 +1,72 @@
> +.. SPDX-License-Identifier: GPL-2.0-or-later
> +
> +Configfs GPIO Simulator
> +===
> +
> +The configfs GPIO Simulator (gpio-sim) 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 sysfs attributes.
> +
> +Creating simulated chips
> +
> +
> +The gpio-sim module registers a configfs subsystem called 'gpio-sim'. It's a
> +subsystem with committable items which means two subdirectories are created
> in
> +the filesystem: pending and live. For more information on configfs and
> +committable items, please refer to Documentation/filesystems/configfs.rst.
> +
> +In order to instantiate a new simulated chip, the user needs to mkdir() a new
> +directory in pending/. Inside each new directory, there's a set of attributes
> +that can be used to configure the new chip. Once the configuration is
> complete,
> +the user needs to use rename() to move the chip to the live/ directory. This
> +creates and registers the new device.
> +
> +In order to destroy a simulated chip, it has to be moved back to pending
> first
> +and then removed using rmdir().
> +
> +Currently supported configuration attributes are:
> +
> + num_lines - an unsigned integer value defining the number of GPIO lines to
> + export
> +
> + label - a string defining the label for the GPIO chip
> +
> + line_names - a list of GPIO line names in the form of quoted strings
> + separated by commas, e.g.: '"foo", "bar", "", "foobar"'. The
> + number of strings doesn't have to be equal to the value set in
> + the num_lines attribute. If it's lower than the number of
> lines,
> + the remaining lines are unnamed. If it's larger, the
> superfluous
> + lines are ignored. A name of the form: '""' means the line
> + should be unnamed.
> +
> +Additionally two read-only attributes named 'chip_name' and 'dev_name' are
> +exposed in order to provide users with a mapping from configfs directories to
> +the actual devices created in the kernel. The former returns the name of the
> +GPIO device as assigned by gpiolib (i.e. "gpiochip0", "gpiochip1", etc.). The
> +latter returns the parent device name as defined by the gpio-sim driver (i.e.
> +"gpio-sim.0", "gpio-sim.1", etc.). This allows user-space to map the configfs
> +items both to the correct character device file as well as the associated
> entry
> +in sysfs.
> +
> +Simulated GPIO chips can also be defined in device-tree. The compatible
> string
> +must be: "gpio-simulator". Supported properties are:
> +
> + "gpio-sim,label" - chip label
> +
> + "gpio-sim,nr-gpios" - number of lines
> +
> +Other standard GPIO properties (like "gpio-line-names" and gpio-hog) are also
> +supported.
> +
> +Manipulating simulated lines
> +
> +
> +Each simulated GPIO chip creates a sysfs attribute group under its device
> +directory called 'line-ctrl'. Inside each group, there's a separate attribute
> +for each GPIO line. The name of the attribute is of the form 'gpioX' where X
> +is 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).
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index e3607ec4c2e8..b6b6150d0d04 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -1633,6 +1633,14 @@ config GPIO_MOCKUP
> tools/testing/selftests/gpio/gpio-mockup.sh. Reference the usage in
> it.
>
> +config GPIO_SIM
> +
