From: Gilles BULOZ <gilles.buloz@kontron.com>
To: Kent Gibson <warthog618@gmail.com>
Cc: Bartosz Golaszewski <brgl@bgdev.pl>, linux-gpio@vger.kernel.org
Subject: Re: [questions] : gpiolib and gpioset behaviour
Date: Mon, 29 Apr 2024 10:50:04 +0200 [thread overview]
Message-ID: <0916be3f-8549-30d2-349d-642f850e0810@kontron.com> (raw)
In-Reply-To: <20240427120902.GA367260@rigel>
On Sat, Apr 27, 2024 at 02:09 PM Kent Gibson wrote:
> On Fri, Apr 26, 2024 at 10:07:20AM +0800, Kent Gibson wrote:
>> On Mon, Apr 22, 2024 at 06:49:05PM +0200, Gilles BULOZ wrote:
>>> On Mon, Apr 22, 2024 at 3:55 PM Bartosz Golaszewski wrote :
>>>> On Mon, Apr 22, 2024 at 2:44 PM Gilles BULOZ <gilles.buloz@kontron.com> wrote:
>>>>>
>>
>> Note that the mask in gc->get_multiple() is unsigned long*, so it is a
>> pointer to an array of unsigned long. Its width is not limited by
>> unsigned long, but by the bits parameter. In your case the mask you pass
>> should contain multiple unsigned longs to achieve 112 bits.
>> Refer to gpiod_get_array_value_complex() for an example of building bitmap
>> masks to pass to gc->get_multiple(), in that case via
>> gpio_chip_get_multiple().
>>
>
> Bah, what was I saying here - both the mask AND bits parameters of
> get_multiple()/set_multiple() are bitmaps of width gc->ngpio, where the
> mask identifies the pins to get/set and bits contains the values.
>
> My bad - must've been before the coffee soaked in.
>
Yes, that's clear to me now thanks to your explainations.
I also understand now the allocation of these "mask" and "bits". I was
missing the fact that gpiod_get_array_value_complex() has two calls to
gpio_chip_get_multiple(), the first without new allocation (value_bitmap
directly passed as last parameter to gpio_chip_get_multiple() and the
second allocating "mask" and "bits" (on FASTPATH_NGPIO bits so 512 bits
by default as set by CONFIG_GPIOLIB_FASTPATH_LIMIT). The second call
is the one used in the path from ioctl GPIO_V2_LINE_GET_VALUES_IOCTL to
the driver so OK.
The same occurs for gpiod_set_array_value_complex() having two calls to
gpio_chip_set_multiple() where the second one is used for ioctl
GPIO_V2_LINE_SET_VALUES_IOCTL.
> Cheers,
> Kent.
>
> .
prev parent reply other threads:[~2024-04-29 8:50 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-22 12:44 [questions] : gpiolib and gpioset behaviour Gilles BULOZ
2024-04-22 15:55 ` Bartosz Golaszewski
2024-04-22 16:49 ` Gilles BULOZ
2024-04-22 18:04 ` Bartosz Golaszewski
2024-04-26 2:07 ` Kent Gibson
2024-04-26 13:08 ` Gilles BULOZ
2024-04-26 13:37 ` Kent Gibson
2024-04-26 16:16 ` Gilles BULOZ
2024-04-27 0:23 ` Kent Gibson
2024-04-27 12:09 ` Kent Gibson
2024-04-29 8:50 ` Gilles BULOZ [this message]
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=0916be3f-8549-30d2-349d-642f850e0810@kontron.com \
--to=gilles.buloz@kontron.com \
--cc=brgl@bgdev.pl \
--cc=linux-gpio@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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.