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From: Kent Gibson <>
Subject: Re: [PATCH v6 0/7] gpio: expose line bias flags to userspace
Date: Tue, 5 Nov 2019 23:26:16 +0800	[thread overview]
Message-ID: <20191105152616.GA19978@sol> (raw)
In-Reply-To: <>

On Tue, Nov 05, 2019 at 10:04:22AM +0800, Kent Gibson wrote:
> Patches are against Bart's gpio/for-kent branch[1].
> The patch has been successfully tested against gpio-mockup, and 
> on a Raspberry Pi, in both cases using the feature/pud_set_config 
> branch of my Go gpiod library[2], as well as with my feature/pud 
> development branch of libgpiod[3].  Patch 7 has only been tested using 
> my gpiod library as libgpiod has not yet been updated to support the 
> SET_CONFIG ioctl.

I've just pushed a first pass at SET_CONFIG support into my libgpiod 
feature/pud branch.  It is causing me a bit of grief.  Due to the way
the libgpiod API is structured, with the direction flags pulled out into 
the request type, I thought it would be cleaner to keep changes to direction 
orthogonal to changes to the other handle flags.

So I've added these methods to the API:

int gpiod_line_set_config(struct gpiod_line *line, int flags)
int gpiod_line_set_direction_input(struct gpiod_line *line)
int gpiod_line_set_direction_output(struct gpiod_line *line,
				    int value)

along with their bulk equivalents.

I've coded that and started adding tests when I tripped over changing
bias.  The kernel requires a direction to be set, but I'm setting it
as-is in gpiod_line_set_config - so that wont work.
Open drain/source are in the same boat - they require output mode.

I see these options:
 1. set the direction as part of gpiod_line_set_config
 2. relax the kernel restriction.
 3. don't support changing bias or open source/drain.
 4. rethink the API.

The first option requires caching the value set for outputs which I'm a
bit hesitant to do, though I'm not sure why - I've already added caching
of the handle flags for the direction functions.

Any preferences or suggestions?


  parent reply	other threads:[~2019-11-05 15:26 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-05  2:04 [PATCH v6 0/7] gpio: expose line bias flags to userspace Kent Gibson
2019-11-05  2:04 ` [PATCH v6 1/7] gpio: expose pull-up/pull-down line " Kent Gibson
2019-11-05  2:04 ` [PATCH v6 2/7] gpiolib: add support for pull up/down to lineevent_create Kent Gibson
2019-11-05  2:04 ` [PATCH v6 3/7] gpiolib: add support for disabling line bias Kent Gibson
2019-11-05  2:04 ` [PATCH v6 4/7] gpiolib: add support for biasing output lines Kent Gibson
2019-11-06 19:39   ` Drew Fustini
2019-11-06 23:56     ` Kent Gibson
2019-11-05  2:04 ` [PATCH v6 5/7] gpio: mockup: add set_config to support pull up/down Kent Gibson
2019-11-05  2:04 ` [PATCH v6 6/7] gpiolib: move validation of line handle flags into helper function Kent Gibson
2019-11-05  2:04 ` [PATCH v6 7/7] gpio: add new SET_CONFIG ioctl() to gpio chardev Kent Gibson
2019-11-05 15:05 ` [PATCH v6 0/7] gpio: expose line bias flags to userspace Bartosz Golaszewski
2019-11-07  8:10   ` Linus Walleij
2019-11-05 15:26 ` Kent Gibson [this message]
2019-11-05 16:24   ` Bartosz Golaszewski
2019-11-05 21:07     ` Bartosz Golaszewski
2019-11-06  6:48       ` Kent Gibson
2019-11-06 13:59         ` Bartosz Golaszewski
2019-11-06 16:58           ` Kent Gibson
2019-11-06 17:06             ` Bartosz Golaszewski
2019-11-06 23:20               ` Kent Gibson
2019-11-07 10:39             ` Kent Gibson
2019-11-07 11:28               ` Bartosz Golaszewski
2019-11-07 12:18                 ` Kent Gibson
2019-11-05 23:15     ` Kent Gibson
2019-11-07 17:57 ` Bartosz Golaszewski
2020-04-15 14:03 ` boards to test gpio line bias flags? Drew Fustini

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