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Message-ID: <CAHp75VeMEngXiFmvTrsW7UZMz0ppR-W-J4D1xU+qKGfLXkG3kg@mail.gmail.com>
Date: Thu, 19 Dec 2019 20:17:30 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Kent Gibson <warthog618@...il.com>,
Linus Walleij <linus.walleij@...aro.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.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 v3 12/13] gpiolib: add new ioctl() for monitoring changes
in line info
On Thu, Dec 19, 2019 at 7:17 PM Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> From: Bartosz Golaszewski <bgolaszewski@...libre.com>
>
> Currently there is no way for user-space to be informed about changes
> in status of GPIO lines e.g. when someone else requests the line or its
> config changes. We can only periodically re-read the line-info. This
> is fine for simple one-off user-space tools, but any daemon that provides
> a centralized access to GPIO chips would benefit hugely from an event
> driven line info synchronization.
>
> This patch adds a new ioctl() that allows user-space processes to reuse
> the file descriptor associated with the character device for watching
> any changes in line properties. Every such event contains the updated
> line information.
>
> Currently the events are generated on three types of status changes: when
> a line is requested, when it's released and when its config is changed.
> The first two are self-explanatory. For the third one: this will only
> happen when another user-space process calls the new SET_CONFIG ioctl()
> as any changes that can happen from within the kernel (i.e.
> set_transitory() or set_debounce()) are of no interest to user-space.
> - } else if (cmd == GPIO_GET_LINEINFO_IOCTL) {
> + } else if (cmd == GPIO_GET_LINEINFO_IOCTL ||
> + cmd == GPIO_GET_LINEINFO_WATCH_IOCTL) {
Wouldn't be better for maintenance to have them separated from the day 1?
...
> + if (test_bit(desc_to_gpio(desc), priv->watched_lines)) {
if (!test_bit(...))
return NOTIFY_DONE;
?
> + pr_debug_ratelimited(
> + "%s: lineinfo event FIFO is full - event dropped\n",
> + __func__);
This is in 99.9% cases redundant in *_dbg() calls.
> + ret = NOTIFY_OK;
> + }
> +
> + return ret;
return NOTIFY_OK;
?
> +}
...
> @@ -3111,6 +3285,7 @@ static int gpio_set_bias(struct gpio_chip *chip, struct gpio_desc *desc)
> if (ret != -ENOTSUPP)
> return ret;
> }
> +
> return 0;
> }
>
This hunk doesn't belong to this patch.
...
> +/**
> + * struct gpioline_info_changed - Information about a change in status
> + * of a GPIO line
> + * @info: updated line information
> + * @timestamp: estimate of time of status change occurrence, in nanoseconds
> + * and GPIOLINE_CHANGED_CONFIG
> + * @event_type: one of GPIOLINE_CHANGED_REQUESTED, GPIOLINE_CHANGED_RELEASED
> + */
> +struct gpioline_info_changed {
> + struct gpioline_info info;
Is this guaranteed to be always 8 byte aligned?
I'm expecting to see some comments there and / or here about it.
> + __u64 timestamp;
> + __u32 event_type;
> + __u32 padding[5]; /* for future use */
> +};
--
With Best Regards,
Andy Shevchenko
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