Re: [PATCH 0/6] GPIO character device skeleton

[Markus Pargmann <mpa@pengutronix.de>]

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On Thu, Oct 22, 2015 at 10:32:24AM +0200, Linus Walleij wrote:
> OK so this is it, I had no patience waiting for users to come up
> with this new ABI, and the requests for a way for userspace to
> use GPIOs properly is coming up again and again. So I created the
> basics for it, so we can then build on top of this to get things
> right. I want to get these very first things right before we go
> wild with setting/getting pin values etc.
> 
> We add ONE ioctl() to get information on the gpiochip. Now we can
> do this (example from ux500):
> 
> root@Ux500:/ lsgpio
> GPIO chip: a03fe000.gpio, 32 GPIO lines
> GPIO chip: 8011e080.gpio, 32 GPIO lines
> GPIO chip: 8011e000.gpio, 32 GPIO lines
> GPIO chip: 8000e180.gpio, 32 GPIO lines
> GPIO chip: 8000e100.gpio, 32 GPIO lines
> GPIO chip: 8000e080.gpio, 32 GPIO lines
> GPIO chip: 8000e000.gpio, 32 GPIO lines
> GPIO chip: 8012e080.gpio, 32 GPIO lines
> GPIO chip: 8012e000.gpio, 32 GPIO lines
> GPIO chip: abx500-gpio, 42 GPIO lines
> GPIO chip: tc3589x, 20 GPIO lines

What happens if we have two I2C gpio expanders with the same I2C
addresses connected to different I2C busses? If I see this correctly
they would both show up with the same name. Is there an easy and
race-free way to see which GPIO chip is connected to which I2C bus?

Best Regards,

Markus

> 
> Johan: I don't have a hot-pluggable GPIO controller :( can you
> do me the favour of testing this and fixing my stupid refcounts
> and race conditions? I only used my brain to try to get things
> right with pluggable GPIO controllers in this patch set, and it
> is bound to fail.
> 
> How to identify and manipulate individual GPIO lines from this
> ABI is a *LATER* *QUESTION*, this is the bare essentials for
> getting there: basic operations on the gpiochip device level.
> 
> Linus Walleij (6):
>   gpio: make the gpiochip a real device
>   gpio: refer to gpio device in prints and debugfs
>   gpio: add a userspace chardev ABI for GPIOs
>   tools/gpio: create GPIO tools
>   gpio: add a userspace character device ABI
>   gpio: ABI: mark the sysfs ABI as obsolete
> 
>  Documentation/ABI/obsolete/sysfs-gpio |  30 ++++++
>  Documentation/ABI/testing/gpio-cdev   |  26 +++++
>  Documentation/ABI/testing/sysfs-gpio  |  28 -----
>  MAINTAINERS                           |   4 +
>  drivers/gpio/gpiolib-sysfs.c          |   2 +-
>  drivers/gpio/gpiolib.c                | 193 +++++++++++++++++++++++++++++++---
>  drivers/gpio/gpiolib.h                |  12 +--
>  include/linux/gpio/driver.h           |  11 +-
>  include/uapi/linux/Kbuild             |   1 +
>  include/uapi/linux/gpio.h             |  28 +++++
>  tools/Makefile                        |   7 +-
>  tools/gpio/Makefile                   |  12 +++
>  tools/gpio/gpio-utils.c               |  11 ++
>  tools/gpio/gpio-utils.h               |  25 +++++
>  tools/gpio/lsgpio.c                   | 128 ++++++++++++++++++++++
>  15 files changed, 462 insertions(+), 56 deletions(-)
>  create mode 100644 Documentation/ABI/obsolete/sysfs-gpio
>  create mode 100644 Documentation/ABI/testing/gpio-cdev
>  delete mode 100644 Documentation/ABI/testing/sysfs-gpio
>  create mode 100644 include/uapi/linux/gpio.h
>  create mode 100644 tools/gpio/Makefile
>  create mode 100644 tools/gpio/gpio-utils.c
>  create mode 100644 tools/gpio/gpio-utils.h
>  create mode 100644 tools/gpio/lsgpio.c
> 
> -- 
> 2.4.3
> 
> 

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