From: Christian Riesch <christian.riesch@omicron.at>
To: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Rodolfo Giometti <giometti@enneenne.com>
Subject: Re: [PATCH] pps: Add support for read operations and return a useful value in poll
Date: Wed, 1 Apr 2015 14:01:36 +0200 [thread overview]
Message-ID: <CABkLObqCWn3WZzs-eMYaBAOYuM6VKxL1Cg1j9Ft05JAjENJXnw@mail.gmail.com> (raw)
In-Reply-To: <20150401081133.GA4384@enneenne.com>
[sent again with Rodolfo in the list of recipients, something went
wrong, sorry!]
Hi Rodolfo,
Thanks for your reply!
On Wed, Apr 1, 2015 at 10:11 AM, Rodolfo Giometti <giometti@enneenne.com> wrote:
> On Tue, Mar 31, 2015 at 11:31:22PM +0200, Christian Riesch wrote:
>> The PPS_FETCH ioctl in drivers/pps/pps.c blocks until a new PPS event
>> occurs, then returns the time stamp data. While this is fine for
>> lots of applications, sometimes it would be nice if the poll system
>> call and a subsequent read could be used to obtain the pps data.
>
> Nak. The read syscall can't be forced to return fix amount of
> data.
I just copied/modified the behavior of ptp_read() in drivers/ptp/ptp_chardev.c:
if (cnt % sizeof(struct ptp_extts_event) != 0)
return -EINVAL;
There the amount of data is forced to be a multiple of sizeof(struct
ptp_extts_event). But if you prefer an ioctl, I can change that of
course.
> Use a dedicated ioctl instead.
Is it ok to pair POLLIN | POLLRDNORM in the poll function with an
ioctl? Or should returning POLLIN | POLLRDNORM mean that a read() will
not block? Should I use POLLPRI instead or something else?
Regards, Christian
prev parent reply other threads:[~2015-04-01 12:01 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-31 21:31 [PATCH] pps: Add support for read operations and return a useful value in poll Christian Riesch
2015-04-01 8:11 ` Rodolfo Giometti
2015-04-01 11:56 ` Christian Riesch
2015-04-01 12:01 ` Christian Riesch [this message]
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=CABkLObqCWn3WZzs-eMYaBAOYuM6VKxL1Cg1j9Ft05JAjENJXnw@mail.gmail.com \
--to=christian.riesch@omicron.at \
--cc=giometti@enneenne.com \
--cc=linux-kernel@vger.kernel.org \
/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).