Re: [PATCH v5 4/4] misc: tps6594-pfsm: Add driver for TI TPS6594 PFSM

[Julien Panis]

On 3/30/23 10:35, Greg KH wrote:
> On Thu, Mar 30, 2023 at 10:20:06AM +0200, Julien Panis wrote:
> > This PFSM controls the operational modes of the PMIC:
> > - STANDBY and LP_STANDBY,
> > - ACTIVE state,
> > - MCU_ONLY state,
> > - RETENTION state, with or without DDR and/or GPIO retention.
> > Depending on the current operational mode, some voltage domains
> > remain energized while others can be off.
> >
> > This PFSM is also used to trigger a firmware update, and provides
> > R/W access to device registers.
> What userspace code uses these new ioctls?  Do you have a pointer to it
> anywhere?

I will provide a user app in 'samples' directory in v6.

> > --- /dev/null
> > +++ b/include/uapi/linux/tps6594_pfsm.h
> > @@ -0,0 +1,45 @@
> > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > +/*
> > + * Userspace ABI for TPS6594 PMIC Pre-configurable Finite State Machine
> > + *
> > + * Copyright (C) 2023 BayLibre Incorporated - https://www.baylibre.com/
> > + */
> > +
> > +#ifndef __TPS6594_PFSM_H
> > +#define __TPS6594_PFSM_H
> > +
> > +#include <linux/const.h>
> > +#include <linux/ioctl.h>
> > +#include <linux/types.h>
> > +
> > +/* PFSM state definitions */
> > +enum pfsm_state {
> > +	PMIC_ACTIVE_STATE,
> > +	PMIC_MCU_ONLY_STATE,
> > +	PMIC_RETENTION_STATE
> > +};
> > +
> > +/**
> > + * struct pmic_state - PMIC state identification
> > + * @state:   PFSM destination state
> > + * @options: options for destination state
> > + */
> > +struct pmic_state {
> > +	enum pfsm_state state;
> > +	__u8 options;
> > +};
> > +
> > +/* Commands */
> > +#define	PMIC_BASE			'P'
> > +
> > +#define	PMIC_GOTO_STANDBY		_IO(PMIC_BASE, 0)
> > +#define	PMIC_GOTO_LP_STANDBY		_IO(PMIC_BASE, 1)
> > +#define	PMIC_UPDATE_PGM			_IO(PMIC_BASE, 2)
> > +#define	PMIC_SET_STATE			_IOW(PMIC_BASE, 3, struct pmic_state)
> > +
> > +/* Options for destination state */
> > +#define PMIC_GPIO_RETENTION		_BITUL(0)
> > +#define PMIC_DDR_RETENTION		_BITUL(1)
> > +#define PMIC_MCU_ONLY_STARTUP_DEST	_BITUL(2)
> Please read Documentation/driver-api/ioctl.rst which says:
>
> * Bitfields and enums generally work as one would expect them to,
>    but some properties of them are implementation-defined, so it is
>    better to avoid them completely in ioctl interfaces.
>
> For a brand-new ioctl interface, you did both of these unrecommended
> things.  Why set yourself for complexity when you do not need to?

I will fix that. Thank you for your feedback.

Julien