linux-kernel - Re: [PATCH] docs: gpio: prefer pread(2) for interrupt reading

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Message-ID: <CAMRc=MeuHpu4_QbgW-6Kc-TGzhcBim7Eb-TZhPax6G2SZHR5iw@mail.gmail.com>
Date: Mon, 27 May 2024 16:54:52 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Huichun Feng <foxhoundsk.tw@...il.com>
Cc: Linus Walleij <linus.walleij@...aro.org>, Jonathan Corbet <corbet@....net>, 
	Kent Gibson <warthog618@...il.com>, linux-gpio@...r.kernel.org, 
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] docs: gpio: prefer pread(2) for interrupt reading

On Tue, May 14, 2024 at 6:12 AM Huichun Feng <foxhoundsk.tw@...il.com> wrote:
>
> In legacy sysfs GPIO, when using poll(2) on the sysfs GPIO value for
> state change awaiting, a subsequent read(2) is required for consuming
> the event, which the doc recommends the use of lseek(2) or
> close-and-reopen to reset the file offset afterwards.
>
> The recommendations however, require at least 2 syscalls to consume
> the event. Gladly, use of pread(2) require only 1 syscall for the
> consumption. Let's advertise this usage by prioritizing its placement.
>
> Signed-off-by: Huichun Feng <foxhoundsk.tw@...il.com>
> ---

This doesn't apply on top of gpio/for-next, please rebase and resend.

Bart