From: Kent Gibson <warthog618@gmail.com>
To: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [PATCH v2 05/18] gpiolib: cdev: support GPIO_GET_LINE_IOCTL and GPIOLINE_GET_VALUES_IOCTL
Date: Sun, 2 Aug 2020 11:31:58 +0800 [thread overview]
Message-ID: <20200802033158.GA13174@sol> (raw)
In-Reply-To: <CAMpxmJWaEVwjXSFHTYmwdfA+88upVkJ4ePSQf_ziSOa1YdOUKQ@mail.gmail.com>
On Fri, Jul 31, 2020 at 06:05:10PM +0200, Bartosz Golaszewski wrote:
> On Sun, Jul 26, 2020 at 3:12 AM Kent Gibson <warthog618@gmail.com> wrote:
> >
>
> [snip]
>
> > >
> > > > +static bool padding_not_zeroed(__u32 *padding, int pad_size)
> > > > +{
> > > > + int i, sum = 0;
> > > > +
> > > > + for (i = 0; i < pad_size; i++)
> > > > + sum |= padding[i];
> > > > +
> > > > + return sum;
> > > > +}
> > >
> > > Reimplementation of memchr_inv() ?
> > >
> >
> > I was hoping to find an existing function, surely checking a region is
> > zeroed is a common thing, right?, so this was a place holder as much
> > as anything. Not sure memchr_inv fits the bill, but I'll give it a
> > try...
> >
>
> If you don't find an appropriate function: please put your new
> implementation in lib/ so that others may reuse it.
>
Changed to memchr_inv.
> > > ...
> > >
> > > > +static u64 gpioline_config_flags(struct gpioline_config *lc, int line_idx)
> > > > +{
> > > > + int i;
> > > > +
> > > > + for (i = lc->num_attrs - 1; i >= 0; i--) {
> > >
> > > Much better to read is
> > >
> > > unsigned int i = lc->num_attrs;
> > >
> > > while (i--) {
> > > ...
> > > }
> > >
> >
> > Really? I find that the post-decrement in the while makes determining the
> > bounds of the loop more confusing.
> >
>
> Agreed, Andy: this is too much nit-picking. :)
>
I was actually hoping for some feedback on the direction of that loop,
as it relates to the handling of multiple instances of the same
attribute associated with a given line.
The reverse loop here implements a last in wins policy, but I'm now
thinking the kernel should be encouraging userspace to only associate a
given attribute with a line once, and that a first in wins would help do
that - as additional associations would be ignored.
Alternatively, the kernel should enforce that an attribute can only be
associated once, but that would require adding more request validation.
> [snip]
>
> > > ...
> > >
> > > > + struct gpio_desc *desc = gpiochip_get_desc(gdev->chip, offset);
> > >
> > > I prefer to see this split, but it's minor.
> > >
> > > > + if (IS_ERR(desc)) {
> > > > + ret = PTR_ERR(desc);
> > > > + goto out_free_line;
> > > > + }
> > >
> > > ...
> > >
> > > > + dev_dbg(&gdev->dev, "registered chardev handle for line %d\n",
> > > > + offset);
> > >
> > > Perhaps tracepoint / event?
> > >
> >
> > Again, a cut-and-paste from V1, and I have no experience with
> > tracepoints or events, so I have no opinion on that.
> >
> > So, yeah - perhaps?
> >
>
> I think it's a good idea to add some proper instrumentation this time
> other than much less reliable logs. Can you take a look at
> include/trace/events/gpio.h? Adding new GPIO trace events should be
> pretty straightforward by copy-pasti... drawing inspiration from
> existing ones.
>
You only want tracepoints to replace those dev_dbg()s, so when a line
is requested? What about the release? Any other points?
Cheers,
Kent.
next prev parent reply other threads:[~2020-08-02 3:32 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-25 4:19 [PATCH v2 00/18] gpio: cdev: add uAPI V2 Kent Gibson
2020-07-25 4:19 ` [PATCH v2 01/18] gpio: uapi: define GPIO_MAX_NAME_SIZE for array sizes Kent Gibson
2020-07-25 4:19 ` [PATCH v2 02/18] gpio: uapi: define uAPI v2 Kent Gibson
2020-08-04 17:42 ` Bartosz Golaszewski
2020-08-05 5:18 ` Kent Gibson
2020-08-05 17:47 ` Bartosz Golaszewski
2020-08-06 1:03 ` Kent Gibson
2020-08-06 1:15 ` Kent Gibson
2020-08-06 15:53 ` Bartosz Golaszewski
2020-07-25 4:19 ` [PATCH v2 03/18] gpiolib: make cdev a build option Kent Gibson
2020-07-25 20:29 ` Andy Shevchenko
2020-07-26 22:25 ` Linus Walleij
2020-07-27 1:46 ` Kent Gibson
2020-07-27 5:57 ` Kent Gibson
2020-07-27 8:15 ` Linus Walleij
2020-07-25 4:19 ` [PATCH v2 04/18] gpiolib: add build option for CDEV v1 ABI Kent Gibson
2020-07-25 4:19 ` [PATCH v2 05/18] gpiolib: cdev: support GPIO_GET_LINE_IOCTL and GPIOLINE_GET_VALUES_IOCTL Kent Gibson
2020-07-25 20:51 ` Andy Shevchenko
2020-07-26 1:12 ` Kent Gibson
2020-07-26 3:24 ` Kent Gibson
2020-07-29 2:28 ` Kent Gibson
2020-07-29 8:05 ` Andy Shevchenko
2020-07-29 10:01 ` Kent Gibson
2020-07-31 16:05 ` Bartosz Golaszewski
2020-08-02 3:31 ` Kent Gibson [this message]
2020-08-02 9:32 ` Kent Gibson
2020-08-03 19:59 ` Bartosz Golaszewski
2020-08-03 20:02 ` Bartosz Golaszewski
2020-08-03 23:01 ` Kent Gibson
2020-08-04 17:47 ` Bartosz Golaszewski
2020-08-05 3:06 ` Kent Gibson
2020-07-25 4:19 ` [PATCH v2 06/18] gpiolib: cdev: support GPIO_GET_LINEINFO_V2_IOCTL and GPIO_GET_LINEINFO_WATCH_V2_IOCTL Kent Gibson
2020-07-25 4:19 ` [PATCH v2 07/18] gpiolib: cdev: support edge detection for uAPI v2 Kent Gibson
2020-08-04 19:28 ` Bartosz Golaszewski
2020-07-25 4:19 ` [PATCH v2 08/18] gpiolib: cdev: support GPIOLINE_SET_CONFIG_IOCTL Kent Gibson
2020-07-25 4:19 ` [PATCH v2 09/18] gpiolib: cdev: support GPIOLINE_SET_VALUES_IOCTL Kent Gibson
2020-07-25 4:19 ` [PATCH v2 10/18] gpiolib: cdev: support setting debounce Kent Gibson
2020-07-25 4:19 ` [PATCH v2 11/18] gpio: uapi: document uAPI v1 as deprecated Kent Gibson
2020-08-04 19:43 ` Bartosz Golaszewski
2020-07-25 4:19 ` [PATCH v2 12/18] tools: gpio: port lsgpio to v2 uAPI Kent Gibson
2020-07-25 4:19 ` [PATCH v2 13/18] tools: gpio: port gpio-watch " Kent Gibson
2020-07-25 4:19 ` [PATCH v2 14/18] tools: gpio: rename nlines to num_lines Kent Gibson
2020-07-25 4:19 ` [PATCH v2 15/18] tools: gpio: port gpio-hammer to v2 uAPI Kent Gibson
2020-07-25 4:19 ` [PATCH v2 16/18] tools: gpio: port gpio-event-mon " Kent Gibson
2020-07-25 4:19 ` [PATCH v2 17/18] tools: gpio: add debounce support to gpio-event-mon Kent Gibson
2020-07-25 4:19 ` [PATCH v2 18/18] tools: gpio: add multi-line monitoring " Kent Gibson
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