linux-kernel - Re: [PATCH v2 11/11] tools: gpio: implement gpio-watch

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Date:   Thu, 5 Dec 2019 10:45:01 +0100
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Kent Gibson <warthog618@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v2 11/11] tools: gpio: implement gpio-watch

śr., 4 gru 2019 o 23:42 Andy Shevchenko <andy.shevchenko@...il.com> napisał(a):
>
> On Wed, Dec 4, 2019 at 7:19 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
> > Add a simple program that allows to test the new LINECHANGED_FD ioctl().
>
> > --- a/tools/gpio/.gitignore
> > +++ b/tools/gpio/.gitignore
> > @@ -1,4 +1,5 @@
> >  gpio-event-mon
> >  gpio-hammer
> >  lsgpio
> > +gpio-watch
>
> Perhaps keep it sorted?
>

Sure I can do this.

> > +++ b/tools/gpio/gpio-watch.c
> > @@ -0,0 +1,112 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * gpio-watch - monitor unrequested lines for property changes using the
> > + *              character device
> > + *
> > + * Copyright (C) 2019 BayLibre SAS
> > + * Author: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > + */
> > +
> > +#include <ctype.h>
> > +#include <errno.h>
> > +#include <fcntl.h>
> > +#include <linux/gpio.h>
> > +#include <poll.h>
> > +#include <stdbool.h>
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <sys/ioctl.h>
> > +#include <unistd.h>
> > +
> > +static bool isnumber(const char *str)
> > +{
> > +       size_t sz = strlen(str);
> > +       int i;
> > +
> > +       for (i = 0; i < sz; i++) {
> > +               if (!isdigit(str[i]))
> > +                       return false;
> > +       }
> > +
> > +       return true;
> > +}
>
> strtoul() will do the same.
>
> char *p;
> unsigned long dummy; // do we need it?
> dummy = strtoul(..., &p);
> return *p == '\0';

Yeah strtoul does allow for error checking. I'll change this in v3.

>
> > +int main(int argc, char **argv)
> > +{
> > +       struct gpioline_info_changed chg;
> > +       struct gpioline_info req;
> > +       struct pollfd pfd;
> > +       int fd, i, j, ret;
> > +       char *event;
> > +       ssize_t rd;
> > +
> > +       if (argc < 3)
> > +               goto err_usage;
> > +
> > +       fd = open(argv[1], O_RDWR | O_CLOEXEC);
> > +       if (fd < 0) {
> > +               perror("unable to open gpiochip");
> > +               return EXIT_FAILURE;
> > +       }
> > +
> > +       for (i = 0, j = 2; i < argc - 2; i++, j++) {
> > +               if (!isnumber(argv[j]))
> > +                       goto err_usage;
> > +
> > +               memset(&req, 0, sizeof(req));
> > +               req.line_offset = atoi(argv[j]);
>
> Oh, why not to call strtoul() directly?
>
> > +
> > +               ret = ioctl(fd, GPIO_GET_LINEINFO_WATCH_IOCTL, &req);
> > +               if (ret) {
> > +                       perror("unable to set up line watch");
>
> Don't you need to unwatch previously added ones?

Nah, we're exiting anyway, the fd will be released.

>
> > +                       return EXIT_FAILURE;
> > +               }
> > +       }
>
> > +       for (;;) {
> > +               ret = poll(&pfd, 1, 5000);
> > +               if (ret < 0) {
> > +                       perror("error polling the linechanged fd");
> > +                       return EXIT_FAILURE;
> > +               } else if (ret > 0) {
> > +                       memset(&chg, 0, sizeof(chg));
>
> > +                       rd = read(pfd.fd, &chg, sizeof(chg));
> > +                       if (rd < 0 || rd != sizeof(chg)) {
> > +                               if (rd != sizeof(chg))
> > +                                       errno = EIO;
> > +
> > +                               perror("error reading line change event");
> > +                               return EXIT_FAILURE;
> > +                       }
>
> Shouldn't we handle the -EINTR?

Indeed we should. Will fix.

Bart

>
> > +               }
> > +       }
> > +
> > +       return 0;
>
>
> --
> With Best Regards,
> Andy Shevchenko