Re: [RFC 1/3] drivers pps: add PPS generators support

[Rodolfo Giometti <giometti@enneenne.com>]

On 09/10/24 04:49, Hall, Christopher S wrote:
> Hi Rudolfo,
> 
>> -----Original Message-----
>> From: Rodolfo Giometti <giometti@enneenne.com>
>> Sent: Tuesday, October 08, 2024 6:51 AM
>> To: linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org
> 
>> Sometimes one needs to be able not only to catch PPS signals but to
>> produce them also. For example, running a distributed simulation,
>> which requires computers' clock to be synchronized very tightly.
>>
>> This patch adds PPS generators class in order to have a well-defined
>> interface for these devices.
>>
>> Signed-off-by: Rodolfo Giometti <giometti@enneenne.com>
>> ---
>>   drivers/pps/Makefile                   |   3 +-
>>   drivers/pps/generators/Kconfig         |  19 +-
>>   drivers/pps/generators/Makefile        |   4 +
>>   drivers/pps/generators/pps_gen-dummy.c |  83 ++++++++
>>   drivers/pps/generators/pps_gen.c       | 283 +++++++++++++++++++++++++
>>   drivers/pps/generators/sysfs.c         |  89 ++++++++
>>   include/linux/pps_gen_kernel.h         |  57 +++++
>>   include/uapi/linux/pps_gen.h           |  35 +++
>>   8 files changed, 571 insertions(+), 2 deletions(-)
>>   create mode 100644 drivers/pps/generators/pps_gen-dummy.c
>>   create mode 100644 drivers/pps/generators/pps_gen.c
>>   create mode 100644 drivers/pps/generators/sysfs.c
>>   create mode 100644 include/linux/pps_gen_kernel.h
>>   create mode 100644 include/uapi/linux/pps_gen.h
> 
> This looks pretty good to me. I would like to see an alarm callback. We are able
> to detect a missed event and rather than stopping inexplicably or writing to the
> system log, it would be better to be able to notify an application directly.
> 
> Off the top of my head, something like:
> 
> void pps_gen_alarm(pps_gen_device *pps_gen) {
> 	pps_gen->alarm = 1;
> 	sysfs_notify(pps_gen->dev->kobj, NULL, "alarm");
> }
> 
> The device is reset by disabling/enabling and this resets the alarm flag.
> 
> Could we add something like this?

Yes, of course. But it's better to provide a proper patch against my patchset V1 
(I'm going to anticipate them to you shortly), since I'm not sure to understand 
what you need.

Ciao,

Rodolfo

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