linux-kernel - Re: [PATCH 05/14] gpio: lpc32xx: allow building on non-lpc32xx targets

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Message-ID: <CAMpxmJUdSnp0QNwWB0rJ1opFrYs9R2KSVS64Tz8X5GDYAJYLpg@mail.gmail.com>
Date:   Mon, 5 Aug 2019 10:27:48 +0200
From:   Bartosz Golaszewski <bgolaszewski@...libre.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     soc@...nel.org, arm-soc <linux-arm-kernel@...ts.infradead.org>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Sylvain Lemieux <slemieux.tyco@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Jason Cooper <jason@...edaemon.net>,
        Andrew Lunn <andrew@...n.ch>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Guenter Roeck <linux@...ck-us.net>,
        linux-gpio <linux-gpio@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, linux-serial@...r.kernel.org,
        USB list <linux-usb@...r.kernel.org>,
        LINUXWATCHDOG <linux-watchdog@...r.kernel.org>,
        Lee Jones <lee.jones@...aro.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 05/14] gpio: lpc32xx: allow building on non-lpc32xx targets

pt., 2 sie 2019 o 13:20 Arnd Bergmann <arnd@...db.de> napisał(a):
>
> On Fri, Aug 2, 2019 at 9:10 AM Bartosz Golaszewski
> <bgolaszewski@...libre.com> wrote:
> > > -#include <mach/hardware.h>
> > > -#include <mach/platform.h>
> > > +#define _GPREG(x)                              (x)
> >
> > What purpose does this macro serve?
> >
> > >
> > >  #define LPC32XX_GPIO_P3_INP_STATE              _GPREG(0x000)
> > >  #define LPC32XX_GPIO_P3_OUTP_SET               _GPREG(0x004)
>
> In the existing code base, this macro converts a register offset to
> an __iomem pointer for a gpio register. I changed the definition of the
> macro here to keep the number of changes down, but I it's just
> as easy to remove it if you prefer.

Could you just add a comment so that it's clear at first glance?

>
> > > @@ -167,14 +166,26 @@ struct lpc32xx_gpio_chip {
> > >         struct gpio_regs        *gpio_grp;
> > >  };
> > >
> > > +void __iomem *gpio_reg_base;
> >
> > Any reason why this can't be made part of struct lpc32xx_gpio_chip?
>
> It could be, but it's the same for each instance, and not known until
> probe() time, so the same pointer would need to be copied into each
> instance that is otherwise read-only.
>
> Let me know if you'd prefer me to rework these two things or leave
> them as they are.

I would prefer not to have global state in the driver, let's just
store the pointer in the data passed to gpiochip_add_data().

Bart

>
> > > +static inline u32 gpreg_read(unsigned long offset)
> >
> > Here and elsewhere: could you please keep the lpc32xx_gpio prefix for
> > all symbols?
>
> Sure.
>
>       Arnd