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 <[email protected]>
---
Documentation/driver-api/gpio/legacy.rst | 6 ++++--
Documentation/userspace-api/gpio/sysfs.rst | 7 ++++---
2 files changed, 8 insertions(+), 5 deletions(-)
diff --git a/Documentation/driver-api/gpio/legacy.rst b/Documentation/driver-api/gpio/legacy.rst
index b6505914791c..c1a083444b0c 100644
--- a/Documentation/driver-api/gpio/legacy.rst
+++ b/Documentation/driver-api/gpio/legacy.rst
@@ -648,8 +648,10 @@ and have the following read/write attributes:
poll(2) will return whenever the interrupt was triggered. If
you use poll(2), set the events POLLPRI. If you use select(2),
set the file descriptor in exceptfds. After poll(2) returns,
- either lseek(2) to the beginning of the sysfs file and read the
- new value or close the file and re-open it to read the value.
+ use pread(2) to read the value at offset zero. Alternatively,
+ either lseek(2) to the beginning of the sysfs file and read
+ the new value or close the file and re-open it to read the
+ value.
"edge" ... reads as either "none", "rising", "falling", or
"both". Write these strings to select the signal edge(s)
diff --git a/Documentation/userspace-api/gpio/sysfs.rst b/Documentation/userspace-api/gpio/sysfs.rst
index 116921048b18..bd64896de91a 100644
--- a/Documentation/userspace-api/gpio/sysfs.rst
+++ b/Documentation/userspace-api/gpio/sysfs.rst
@@ -97,9 +97,10 @@ and have the following read/write attributes:
poll(2) will return whenever the interrupt was triggered. If
you use poll(2), set the events POLLPRI and POLLERR. If you
use select(2), set the file descriptor in exceptfds. After
- poll(2) returns, either lseek(2) to the beginning of the sysfs
- file and read the new value or close the file and re-open it
- to read the value.
+ poll(2) returns, use pread(2) to read the value at offset
+ zero. Alternatively, either lseek(2) to the beginning of the
+ sysfs file and read the new value or close the file and
+ re-open it to read the value.
"edge" ...
reads as either "none", "rising", "falling", or
--
2.34.1
On Tue, May 14, 2024 at 12:12:23PM +0800, Huichun Feng 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 <[email protected]>
LGTM, thanks!
Reviewed-by: Bagas Sanjaya <[email protected]>
--
An old man doll... just what I always wanted! - Clara
Kindly ping.
Sorry that the last ping wasn't sent in plain text.
Huichun Feng <[email protected]> 於 2024年5月14日 週二 下午12:12寫道：
>
> 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 <[email protected]>
> ---
> Documentation/driver-api/gpio/legacy.rst | 6 ++++--
> Documentation/userspace-api/gpio/sysfs.rst | 7 ++++---
> 2 files changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/driver-api/gpio/legacy.rst b/Documentation/driver-api/gpio/legacy.rst
> index b6505914791c..c1a083444b0c 100644
> --- a/Documentation/driver-api/gpio/legacy.rst
> +++ b/Documentation/driver-api/gpio/legacy.rst
> @@ -648,8 +648,10 @@ and have the following read/write attributes:
> poll(2) will return whenever the interrupt was triggered. If
> you use poll(2), set the events POLLPRI. If you use select(2),
> set the file descriptor in exceptfds. After poll(2) returns,
> - either lseek(2) to the beginning of the sysfs file and read the
> - new value or close the file and re-open it to read the value.
> + use pread(2) to read the value at offset zero. Alternatively,
> + either lseek(2) to the beginning of the sysfs file and read
> + the new value or close the file and re-open it to read the
> + value.
>
> "edge" ... reads as either "none", "rising", "falling", or
> "both". Write these strings to select the signal edge(s)
> diff --git a/Documentation/userspace-api/gpio/sysfs.rst b/Documentation/userspace-api/gpio/sysfs.rst
> index 116921048b18..bd64896de91a 100644
> --- a/Documentation/userspace-api/gpio/sysfs.rst
> +++ b/Documentation/userspace-api/gpio/sysfs.rst
> @@ -97,9 +97,10 @@ and have the following read/write attributes:
> poll(2) will return whenever the interrupt was triggered. If
> you use poll(2), set the events POLLPRI and POLLERR. If you
> use select(2), set the file descriptor in exceptfds. After
> - poll(2) returns, either lseek(2) to the beginning of the sysfs
> - file and read the new value or close the file and re-open it
> - to read the value.
> + poll(2) returns, use pread(2) to read the value at offset
> + zero. Alternatively, either lseek(2) to the beginning of the
> + sysfs file and read the new value or close the file and
> + re-open it to read the value.
>
> "edge" ...
> reads as either "none", "rising", "falling", or
> --
> 2.34.1
>
On Mon, May 27, 2024 at 9:05 AM Huichun Feng <[email protected]> wrote:
>
> Kindly ping.
>
> Sorry that the last ping wasn't sent in plain text.
>
>
Please don't ping me on the morning of the day after the merge window
closes. I don't pick up patches for the next release during the merge
window (like most maintainers) and I need some time to catch up on my
queue during rc1.
Bart
On Tue, May 14, 2024 at 6:12 AM Huichun Feng <[email protected]> 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 <[email protected]>
> ---
This doesn't apply on top of gpio/for-next, please rebase and resend.
Bart
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 <[email protected]>
---
Documentation/userspace-api/gpio/sysfs.rst | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/Documentation/userspace-api/gpio/sysfs.rst b/Documentation/userspace-api/gpio/sysfs.rst
index 116921048..bd64896de 100644
--- a/Documentation/userspace-api/gpio/sysfs.rst
+++ b/Documentation/userspace-api/gpio/sysfs.rst
@@ -97,9 +97,10 @@ and have the following read/write attributes:
poll(2) will return whenever the interrupt was triggered. If
you use poll(2), set the events POLLPRI and POLLERR. If you
use select(2), set the file descriptor in exceptfds. After
- poll(2) returns, either lseek(2) to the beginning of the sysfs
- file and read the new value or close the file and re-open it
- to read the value.
+ poll(2) returns, use pread(2) to read the value at offset
+ zero. Alternatively, either lseek(2) to the beginning of the
+ sysfs file and read the new value or close the file and
+ re-open it to read the value.
"edge" ...
reads as either "none", "rising", "falling", or
--
2.34.1
On Sun, Jun 2, 2024 at 9:49 AM Huichun Feng <[email protected]> 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 <[email protected]>
> ---
> Documentation/userspace-api/gpio/sysfs.rst | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/userspace-api/gpio/sysfs.rst b/Documentation/userspace-api/gpio/sysfs.rst
> index 116921048..bd64896de 100644
> --- a/Documentation/userspace-api/gpio/sysfs.rst
> +++ b/Documentation/userspace-api/gpio/sysfs.rst
> @@ -97,9 +97,10 @@ and have the following read/write attributes:
> poll(2) will return whenever the interrupt was triggered. If
> you use poll(2), set the events POLLPRI and POLLERR. If you
> use select(2), set the file descriptor in exceptfds. After
> - poll(2) returns, either lseek(2) to the beginning of the sysfs
> - file and read the new value or close the file and re-open it
> - to read the value.
> + poll(2) returns, use pread(2) to read the value at offset
> + zero. Alternatively, either lseek(2) to the beginning of the
> + sysfs file and read the new value or close the file and
> + re-open it to read the value.
>
> "edge" ...
> reads as either "none", "rising", "falling", or
> --
> 2.34.1
>
Please don't send new versions of a patch as responses in an email
thread. Otherwise tools such as b4 cannot tell if it's a new version
or part of a larger series. Please always start a new thread with get
send-email or - better yet - start using b4 and let it manage the
series for you. Please resend this correctly.
Bart