Date: Fri, 27 Nov 2020 15:05:02 -0700 From: Ian Lepore <ian@freebsd.org> To: freebsd-arm@freebsd.org Subject: Re: User Space GPIO Interrupt programming - GSoC-2018 Message-ID: <d3d830aed6b4323ccdfbb85e5ea0849a2009faa4.camel@freebsd.org> In-Reply-To: <1e6993d43d22d6ce1aa2860a61745356688d1e53.camel@freebsd.org> References: <2B01780F-D367-48A3-A827-B479030A496D@obsigna.com> <c55d7f332631b69c3241a60538a6a7b5475d93b9.camel@freebsd.org> <FBEF19B1-0504-4CDF-976C-C50707E06584@obsigna.com> <8d806302-479c-ca34-3fdb-96d27f40e212@viruzzz.org> <8655AF30-273B-48E7-98CD-007AA1D265F5@obsigna.com> <54ffe2d2-01a2-8b43-94fa-aee4a3f89861@viruzzz.org> <08649892ca2ab434c261d36e0e13ba051086de6f.camel@freebsd.org> <1e6993d43d22d6ce1aa2860a61745356688d1e53.camel@freebsd.org>
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On Fri, 2020-11-27 at 11:04 -0700, Ian Lepore wrote:
> > I think we need a way for the app to choose whether it wants simple
> > reporting of pin number (like the original code) perhaps along with
> > a count, versus requesting detailed per-event data. I'm going to
> > propose something more detailed about this as soon as I get my
> > thoughts all organized.
Okay, here's my current thinking on this (with tabs compressed down to
just a couple spaces to prevent line-wrap in email). This is a snippet
from gpio.h...
/*
* Reporting gpio pin-change per-event details to userland.
*
* When configured for detail reporting, each call to read(2) will
* return one or more of these structures (or will return
* EWOULDBLOCK in non-blocking IO mode when there are no new events
* to report).
*/
struct gpio_event_detail {
struct timespec gp_time; /* Time of event */
uint16_t gp_pin; /* Pin number */
bool gp_pinstate; /* Pin state at time of event */
};
/*
* Reporting gpio pin-change summary data to userland.
*
* When configured for summary reporting (the default), each call to
* read(2) will return one or more of these structures (or will
* return EWOULDBLOCK in non-blocking IO mode when there are no new
* events to report).
*/
struct gpio_event_summary {
struct timespec gp_first_time; /* Time of first event */
struct timespec gp_last_time; /* Time of last event */
uint16_t gp_pin; /* Pin number */
uint16_t gp_count; /* Event count */
bool gp_first_state; /* Pin state at first event */
bool gp_last_state; /* Pin state at last event */
};
/*
* Configuring event reporting to userland.
*
* The default is to deliver gpio_event_summary reporting. To
* change it, you must use the GPIOCONFIGEVENTS ioctl to set the
* event fifo size before using GPIOSETCONFIG to configure reporting
* interrupt events on any pins. This config is tracked on a
* per-open-descriptor basis. Once it has been set, it cannot be
* changed without closing and re-opening the file descriptor.
*/
struct gpio_event_config {
uint32_t gp_fifo_size; /* Zero for summary reporting. */
};
#define GPIOCONFIGEVENTS _IOW('G', 9, struct gpio_event_config)
I haven't written the implementation of all this yet, but I have a
pretty good idea of how to do so.
-- Ian
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