Hi Sean,
On 11/3/18 12:22 PM, Sean Young wrote:
> Hi Michael,
>
> On Fri, Nov 02, 2018 at 12:43:41PM +0100, Michael Kerrisk (man-pages) wrote:
>> Hi Sean,
>>
>> On 11/02/2018 12:04 PM, Sean Young wrote:
>>> Signed-off-by: Sean Young <sean@xxxxxxxx>
>>> ---
>>> man4/lirc.4 | 9 ++++++++-
>>> 1 file changed, 8 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/man4/lirc.4 b/man4/lirc.4
>>> index 526d8432c..6e9a94a66 100644
>>> --- a/man4/lirc.4
>>> +++ b/man4/lirc.4
>>> @@ -273,7 +273,14 @@ is 1) or disable
>>> .RI ( val
>>> is 0) timeout packages in
>>> .BR LIRC_MODE_MODE2 .
>>> -By default, timeout reports should be turned off.
>>> +Each time the
>>> +.BR lirc
>>> +device is opened, timeout reports are enabled for that
>>> +file descriptor since kernel release 4.16.
>>> +In earlier releases, timeout reports were disabled by default, and once
>>> +enabled, enabled for all
>>> +.BR lirc
>>> +file descriptors until turned off again.
>>> .TP
>>> .BR LIRC_SET_REC_CARRIER " (\fIint\fP)"
>>> Set the receive carrier frequency (Hz).
>>
>> I've applied this patch, and also tweaked the text somewhat.
>> Could you take a look please?
>
> Looks good I think. Thanks for fixing up my badly-phrases phrases. :)
No problem :-). Thanks for all the patches.
>
>> One thing I'm still not clear about... Since kernel 4.16,
>> does enabling LIRC_SET_REC_TIMEOUT on an FD referring to a
>> lirc device cause all subsequently opened FDs on the lirc
>> device to have timeouts enabled? The existing text suggests
>> that, but it sounds like odd behavior.
>
> The LIRC_SET_REC_TIMEOUT feature is maintained per-fd, so for each newly
> opened fd, it is enabled.
Sorry, I'm still not clear. Let's look at the current
text, as it looks after my light edits of your patch:
LIRC_SET_REC_TIMEOUT_REPORTS (int)
Enable (val is 1) or disable (val is 0) timeout packages in
LIRC_MODE_MODE2. The behavior of this operation has varied
across kernel versions:
* Since Linux 4.16: each time the lirc device is opened,
timeout reports are enabled for that file descriptor.
* In Linux 4.15 and earlier: timeout reports were disabled
by default, and enabling them had effect for all lirc
file descriptors until timeouts were disabled again.
The 4.16+ text makes it sound like:
a) You use the ioctl() to set a timeout attribute on the lirc device,
and
b) All subsequently opened FDs on that device inherit that attribute.
But, I think that interpretation is not correct(?).
So, explain to me, in Linux 4.16+ what code steps would I make
to open a lirc device and set the timeout. (And would those
steps have any effect on already opened FDs for the lirc device,
or for ant subsequently opened FDs?)
Also, I read the Linux <= 4.15 text to mean that enabling or
disabling timeouts on one lirc FDs affects all currently open
FDs for that lirc device, as well as any subsequently opened
devices. Is that correct?
Thanks,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
