From: Kent Gibson <warthog618@gmail.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
Linus Walleij <linus.walleij@linaro.org>,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v9 04/20] gpio: uapi: define uAPI v2
Date: Wed, 23 Sep 2020 18:30:31 +0800 [thread overview]
Message-ID: <20200923103031.GA579645@sol> (raw)
In-Reply-To: <CAHp75VewJYDQ1Moi4jw=wbBMLNpaUGPgz+AsPjNdZqtHCgkjwA@mail.gmail.com>
On Wed, Sep 23, 2020 at 01:04:05PM +0300, Andy Shevchenko wrote:
> On Tue, Sep 22, 2020 at 5:34 AM Kent Gibson <warthog618@gmail.com> wrote:
> >
[snip]
> > There is also some minor renaming of fields for consistency compared to
> > their v1 counterparts, e.g. offset rather than lineoffset or line_offset,
> > and consumer rather than consumer_label.
> >
> > Additionally, v1 GPIOHANDLES_MAX becomes GPIO_V2_LINES_MAX in v2 for
> > clarity, and the gpiohandle_data __u8 array becomes a bitmap in
> > gpio_v2_line_values.
> >
> > The v2 uAPI is mostly a reorganisation and extension of v1, so userspace
> > code, particularly libgpiod, should readily port to it.
>
> ...
>
> > +struct gpio_v2_line_config {
> > + __aligned_u64 flags;
> > + __u32 num_attrs;
>
> > + /* Pad to fill implicit padding and reserve space for future use. */
> > + __u32 padding[5];
>
> Probably I somehow missed the answer, but why do we need 5 here and not 1?
>
Sorry, I got tired of repeating myself, and just acked that we disagree
on the approach here.
Your suggestion to use the size for version would result in an
explosion of ioctl signatures - every time we add a field we have to add
a new ioctl and handle it separately in gpio_ioctl() or linereq_ioctl().
Instead what we do here is reserve some space for future use - that we
can replace with fields without changing the signature.
The padding is required to be zeroed now, and any future use will take
a 0 to mean "leave alone".
The sizes are a guestimate as to what may be needed in the future, and
as such are almost certainly wrong - but hopefully on the high side.
If that fails we can always fall back to your approach.
Cheers,
Kent.
next prev parent reply other threads:[~2020-09-23 10:30 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 2:31 [PATCH v9 00/20] gpio: cdev: add uAPI v2 Kent Gibson
2020-09-22 2:31 ` [PATCH v9 01/20] gpiolib: cdev: gpio_desc_to_lineinfo() should set info offset Kent Gibson
2020-09-22 2:31 ` [PATCH v9 02/20] gpiolib: cdev: replace strncpy() with strscpy() Kent Gibson
2020-09-22 2:31 ` [PATCH v9 03/20] gpio: uapi: define GPIO_MAX_NAME_SIZE for array sizes Kent Gibson
2020-09-22 2:31 ` [PATCH v9 04/20] gpio: uapi: define uAPI v2 Kent Gibson
2020-09-22 7:41 ` Arnd Bergmann
2020-09-22 9:50 ` Bartosz Golaszewski
2020-09-22 10:07 ` Kent Gibson
2020-09-28 13:42 ` strace decoding for GPIO uAPI Kent Gibson
2020-09-29 13:20 ` Bartosz Golaszewski
2020-09-29 15:04 ` Kent Gibson
2020-09-29 16:19 ` Andy Shevchenko
2020-09-23 10:04 ` [PATCH v9 04/20] gpio: uapi: define uAPI v2 Andy Shevchenko
2020-09-23 10:30 ` Kent Gibson [this message]
2020-09-23 11:16 ` Andy Shevchenko
2020-09-23 12:18 ` Arnd Bergmann
2020-09-23 15:15 ` Andy Shevchenko
2020-09-22 2:31 ` [PATCH v9 05/20] gpiolib: make cdev a build option Kent Gibson
2020-09-22 2:31 ` [PATCH v9 06/20] gpiolib: add build option for CDEV v1 ABI Kent Gibson
2020-09-22 2:31 ` [PATCH v9 07/20] gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL Kent Gibson
2020-09-23 11:11 ` Andy Shevchenko
2020-09-24 8:09 ` Kent Gibson
2020-09-25 10:06 ` Andy Shevchenko
2020-09-26 9:16 ` Kent Gibson
2020-09-27 9:00 ` Andy Shevchenko
2020-09-27 12:39 ` Kent Gibson
2020-09-24 14:29 ` Bartosz Golaszewski
2020-09-22 2:31 ` [PATCH v9 08/20] gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL Kent Gibson
2020-09-23 15:41 ` Andy Shevchenko
2020-09-24 2:39 ` Kent Gibson
2020-09-24 8:39 ` Andy Shevchenko
2020-09-24 9:48 ` Kent Gibson
2020-09-25 10:12 ` Andy Shevchenko
2020-09-25 11:56 ` Kent Gibson
2020-09-25 14:43 ` Andy Shevchenko
2020-09-25 5:32 ` Kent Gibson
2020-09-22 2:31 ` [PATCH v9 09/20] gpiolib: cdev: support edge detection for uAPI v2 Kent Gibson
2020-09-23 15:47 ` Andy Shevchenko
2020-09-24 3:07 ` Kent Gibson
2020-09-25 9:35 ` Andy Shevchenko
2020-09-25 12:26 ` Kent Gibson
2020-09-25 14:48 ` Andy Shevchenko
2020-09-22 2:31 ` [PATCH v9 10/20] gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL Kent Gibson
2020-09-23 16:14 ` Andy Shevchenko
2020-09-23 16:15 ` Andy Shevchenko
2020-09-24 3:24 ` Kent Gibson
2020-09-24 8:26 ` Andy Shevchenko
2020-09-24 9:26 ` Kent Gibson
2020-09-25 9:49 ` Andy Shevchenko
2020-09-22 2:31 ` [PATCH v9 11/20] gpiolib: cdev: support GPIO_V2_LINE_SET_VALUES_IOCTL Kent Gibson
2020-09-23 16:18 ` Andy Shevchenko
2020-09-24 7:32 ` Kent Gibson
2020-09-24 8:21 ` Andy Shevchenko
2020-09-24 9:08 ` Kent Gibson
2020-09-24 12:46 ` Kent Gibson
2020-09-25 9:57 ` Andy Shevchenko
2020-09-25 12:16 ` Kent Gibson
2020-09-22 2:31 ` [PATCH v9 12/20] gpiolib: cdev: support setting debounce Kent Gibson
2020-09-23 16:27 ` Andy Shevchenko
2020-09-24 7:48 ` Kent Gibson
2020-09-25 9:43 ` Andy Shevchenko
2020-09-22 2:31 ` [PATCH v9 13/20] gpio: uapi: document uAPI v1 as deprecated Kent Gibson
2020-09-22 7:49 ` Arnd Bergmann
2020-09-22 8:11 ` Andy Shevchenko
2020-09-22 9:05 ` Kent Gibson
2020-09-22 2:31 ` [PATCH v9 14/20] tools: gpio: port lsgpio to v2 uAPI Kent Gibson
2020-09-22 2:31 ` [PATCH v9 15/20] tools: gpio: port gpio-watch " Kent Gibson
2020-09-22 2:31 ` [PATCH v9 16/20] tools: gpio: rename nlines to num_lines Kent Gibson
2020-09-22 2:31 ` [PATCH v9 17/20] tools: gpio: port gpio-hammer to v2 uAPI Kent Gibson
2020-09-23 16:30 ` Andy Shevchenko
2020-09-24 7:50 ` Kent Gibson
2020-09-22 2:31 ` [PATCH v9 18/20] tools: gpio: port gpio-event-mon " Kent Gibson
2020-09-22 2:31 ` [PATCH v9 19/20] tools: gpio: add multi-line monitoring to gpio-event-mon Kent Gibson
2020-09-22 2:31 ` [PATCH v9 20/20] tools: gpio: add debounce support " Kent Gibson
2020-09-23 16:35 ` [PATCH v9 00/20] gpio: cdev: add uAPI v2 Andy Shevchenko
2020-09-24 8:00 ` Kent Gibson
2020-09-25 9:44 ` Andy Shevchenko
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