linux-arm-kernel.lists.infradead.org archive mirror
 help / color / mirror / Atom feed
From: David Lechner <david@lechnology.com>
To: William Breathitt Gray <vilhelm.gray@gmail.com>,
	Pavel Machek <pavel@ucw.cz>
Cc: kamel.bouhara@bootlin.com, gwendal@chromium.org,
	alexandre.torgue@st.com, linux-iio@vger.kernel.org,
	patrick.havelange@essensium.com, alexandre.belloni@bootlin.com,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org, mcoquelin.stm32@gmail.com,
	syednwaris@gmail.com, linux-stm32@st-md-mailman.stormreply.com,
	jic23@kernel.org
Subject: Re: [PATCH v5 4/5] docs: counter: Document character device interface
Date: Mon, 12 Oct 2020 12:04:10 -0500	[thread overview]
Message-ID: <d06d5e47-5776-85ee-0dc5-8b624e36d83d@lechnology.com> (raw)
In-Reply-To: <20201008122845.GA3314@shinobu>

On 10/8/20 7:28 AM, William Breathitt Gray wrote:
> On Thu, Oct 08, 2020 at 10:09:09AM +0200, Pavel Machek wrote:
>> Hi!
>>
>>> +        int main(void)
>>> +        {
>>> +                struct pollfd pfd = { .events = POLLIN };
>>> +                struct counter_event event_data[2];
>>> +
>>> +                pfd.fd = open("/dev/counter0", O_RDWR);
>>> +
>>> +                ioctl(pfd.fd, COUNTER_SET_WATCH_IOCTL, watches);
>>> +                ioctl(pfd.fd, COUNTER_SET_WATCH_IOCTL, watches + 1);
>>> +                ioctl(pfd.fd, COUNTER_LOAD_WATCHES_IOCTL);
>>> +
>>> +                for (;;) {
>>> +                        poll(&pfd, 1, -1);
>>
>> Why do poll, when you are doing blocking read?
>>
>>> +                        read(pfd.fd, event_data,  sizeof(event_data));
>>
>> Does your new chrdev always guarantee returning complete buffer?
>>
>> If so, should it behave like that?
>>
>> Best regards,
>> 									Pavel
>> -- 
>> (english) http://www.livejournal.com/~pavelmachek
>> (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
> 
> I suppose you're right: a poll() should be redundant now with this
> version of the character device implementation because buffers will
> always return complete; so a blocking read() should achieve the same
> behavior that a poll() with read() would.
> 
> I'll give some more time for additional feedback to come in for this
> version of the patchset, and then likely remove support for poll() in
> the v6 submission.
> 
> William Breathitt Gray
> 

I hope that you mean that you will just remove it from the example
and not from the chardev. Otherwise it won't be possible to
integrate this with an event loop.


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2020-10-12 17:06 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-27  2:18 [PATCH v5 0/5] Introduce the Counter character device interface William Breathitt Gray
2020-09-27  2:18 ` [PATCH v5 2/5] docs: counter: Update to reflect sysfs internalization William Breathitt Gray
2020-09-27  2:18 ` [PATCH v5 3/5] counter: Add character device interface William Breathitt Gray
2020-10-14  1:40   ` David Lechner
2020-10-18 16:49     ` William Breathitt Gray
2020-10-20 15:53       ` David Lechner
2020-10-25 12:55         ` William Breathitt Gray
2020-10-25 16:36           ` David Lechner
2020-10-14 17:43   ` David Lechner
2020-10-14 19:05     ` William Breathitt Gray
2020-10-14 22:32       ` David Lechner
2020-10-14 22:40   ` David Lechner
2020-10-18 16:58     ` William Breathitt Gray
2020-10-20 16:06       ` David Lechner
2020-10-25 13:18         ` William Breathitt Gray
2020-10-25 16:34           ` David Lechner
2020-10-25 17:53             ` William Breathitt Gray
2020-09-27  2:18 ` [PATCH v5 4/5] docs: counter: Document " William Breathitt Gray
2020-10-08  8:09   ` Pavel Machek
2020-10-08 12:28     ` William Breathitt Gray
2020-10-12 17:04       ` David Lechner [this message]
2020-10-13 18:58         ` William Breathitt Gray
2020-10-13 19:08           ` David Lechner
2020-10-13 19:27             ` William Breathitt Gray
2020-09-27  2:18 ` [PATCH v5 5/5] counter: 104-quad-8: Add IRQ support for the ACCES 104-QUAD-8 William Breathitt Gray
2020-10-14  0:13   ` David Lechner
2020-10-18 14:50     ` William Breathitt Gray
2020-10-13  0:35 ` [PATCH v5 0/5] Introduce the Counter character device interface David Lechner
2020-10-18 14:14   ` William Breathitt Gray
     [not found] ` <e38f6dc3a08bf2510034334262776a6ed1df8b89.1601170670.git.vilhelm.gray@gmail.com>
2020-10-13  2:15   ` [PATCH v5 1/5] counter: Internalize sysfs interface code David Lechner
2020-10-18 14:49     ` William Breathitt Gray
2020-10-20 15:38       ` David Lechner
2020-10-23 13:12         ` William Breathitt Gray
2020-10-15  1:38   ` David Lechner
2020-10-18 17:00     ` William Breathitt Gray

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=d06d5e47-5776-85ee-0dc5-8b624e36d83d@lechnology.com \
    --to=david@lechnology.com \
    --cc=alexandre.belloni@bootlin.com \
    --cc=alexandre.torgue@st.com \
    --cc=gwendal@chromium.org \
    --cc=jic23@kernel.org \
    --cc=kamel.bouhara@bootlin.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-iio@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-stm32@st-md-mailman.stormreply.com \
    --cc=mcoquelin.stm32@gmail.com \
    --cc=patrick.havelange@essensium.com \
    --cc=pavel@ucw.cz \
    --cc=syednwaris@gmail.com \
    --cc=vilhelm.gray@gmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).