Re: [PATCH 1/2] iio: light: ltr390: Add sysfs attribute to report data freshness

[Akshay Jindal]

Thanks David for the swift and valuable feedback. Please find replies inline.

On Tue, Jul 22, 2025 at 1:55 AM David Lechner <dlechner@xxxxxxxxxxxx> wrote:
>
> For debugging, using debugfs would make more sense.
Will it make sense if I simply give register access via debugfs?
Something like this:
static const struct iio_info ad7606_info_sw_mode = {
    .read_raw = &ad7606_read_raw,
    .write_raw = &ad7606_write_raw,
    .debugfs_reg_access = &ad7606_reg_access,<---------
    .validate_trigger = &ad7606_validate_trigger,
    .update_scan_mode = &ad7606_update_scan_mode,
};
This way the information about data status will be available on demand,
without exposing any special sysfs attribute.
>
> For application level filtering, why does it matter if we have
> read the same value before or not? The sampling_frequency is
> available, so the application should be able to deduce when
> fresh data should be available based on time.
Agreed.
>
> I could see maybe polling this in the kernel in order to implement
> a buffered capture mode, but not sure passing this on to userspace
> is the best way to go about it.
I had sent 2 patches. This was my PATCH 1 of 2. In patch 2 of 2,
I have done something similar to what you mentioned, not exactly polling,
but reading the data status bit before reading actual data.
Both patches are independent. Please have a look at that as well.

Thanks,
Akshay