From: "Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>
To: Kent Gibson <warthog618@gmail.com>
Cc: linux-pwm@vger.kernel.org, kernel@pengutronix.de
Subject: Re: [PATCH 8/8] pwm: Add support for pwmchip devices for faster and easier userspace access
Date: Tue, 7 May 2024 08:12:15 +0200 [thread overview]
Message-ID: <vr6abwhdc33u6tbymbu2x77lg3abqr57oi2ia34am3xu2n2ohv@xltf3jxjac3f> (raw)
In-Reply-To: <20240507011103.GA26136@rigel>
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On Tue, May 07, 2024 at 09:11:03AM +0800, Kent Gibson wrote:
> On Sun, Mar 17, 2024 at 11:40:39AM +0100, Uwe Kleine-König wrote:
> > With this change each pwmchip can be accessed from userspace via a
> > character device. Compared to the sysfs-API this is faster (on a
> > stm32mp157 applying a new configuration takes approx 25% only) and
> > allows to pass the whole configuration in a single ioctl.
> >
> > Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
>
> > new file mode 100644
> > index 000000000000..ca765bfaa68d
> > --- /dev/null
> > +++ b/include/uapi/linux/pwm.h
> > @@ -0,0 +1,23 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
> > +
> > +#ifndef _UAPI_PWM_H_
> > +#define _UAPI_PWM_H_
> > +
> > +#include <linux/ioctl.h>
> > +#include <linux/types.h>
> > +
> > +struct pwmchip_state {
> > + unsigned int hwpwm;
> > + __u64 period;
> > + __u64 duty_cycle;
> > + __u64 duty_offset;
> > +};
> > +
>
> Sorry for being late to the party, but I only ran across this thread by
> accident.
>
> Have you considered the implications of sizing and alignment here[1]?
>
> Change this to:
>
> struct pwmchip_state {
> __u32 hwpwm;
> __u32 __pad;
> __u64 period;
> __u64 duty_cycle;
> __u64 duty_offset;
> };
>
> to clarify?
Good catch. There is some pending rework necessary for the inner
mechanism of the pwm framework that has to be done before the ioctl goes
into the mainline. So you're not (too) late with your concerns.
I'll take care of the explicit padding.
Thanks for your attention,
Uwe
--
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | https://www.pengutronix.de/ |
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next prev parent reply other threads:[~2024-05-07 6:12 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-17 10:40 [PATCH 0/8] pwm: Add support for character devices Uwe Kleine-König
2024-03-17 10:40 ` [PATCH 1/8] pwm: Ensure that pwm_chips are allocated using pwmchip_alloc() Uwe Kleine-König
2024-03-17 10:40 ` [PATCH 2/8] pwm: Give some sysfs related variables and functions better names Uwe Kleine-König
2024-03-17 10:40 ` [PATCH 3/8] pwm: Move contents of sysfs.c into core.c Uwe Kleine-König
2024-03-17 10:40 ` [PATCH 4/8] pwm: Ensure a struct pwm has the same lifetime as its pwm_chip Uwe Kleine-König
2024-03-17 10:40 ` [PATCH 5/8] pwm: Add a struct device to struct pwm_chip Uwe Kleine-König
2024-03-28 18:44 ` David Lechner
2024-03-29 10:19 ` Uwe Kleine-König
2024-03-17 10:40 ` [PATCH 6/8] pwm: Make pwmchip_[sg]et_drvdata() a wrapper around dev_set_drvdata() Uwe Kleine-König
2024-03-17 10:40 ` [PATCH 7/8] pwm: Add more locking Uwe Kleine-König
2024-03-18 7:28 ` Thorsten Scherer
[not found] ` <CGME20240404120932eucas1p1b3c1e07bf6f41f6330725148b0268b13@eucas1p1.samsung.com>
2024-04-04 12:09 ` Marek Szyprowski
2024-04-04 15:33 ` Uwe Kleine-König
2024-03-17 10:40 ` [PATCH 8/8] pwm: Add support for pwmchip devices for faster and easier userspace access Uwe Kleine-König
2024-04-08 15:42 ` John Ernberg
2024-04-09 7:49 ` Uwe Kleine-König
2024-04-15 11:27 ` John Ernberg
2024-05-07 1:11 ` Kent Gibson
2024-05-07 6:12 ` Uwe Kleine-König [this message]
2024-04-13 9:22 ` [PATCH 0/8] pwm: Add support for character devices Uwe Kleine-König
2024-04-22 18:59 ` David Lechner
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