Re: [PATCH] iio: adc: ti-ads7950: use spi_optimize_message()

[Andy Shevchenko]

On Tue, Apr 14, 2026 at 08:29:29AM -0500, David Lechner wrote:
> On 4/14/26 4:54 AM, Andy Shevchenko wrote:
> > On Sat, Apr 11, 2026 at 05:13:33PM -0500, David Lechner wrote:
> >> Use spi_optimize_message() to reduce CPU usage during buffered reads.
> >>
> >> On hardware with support for SPI_CS_WORD, this reduced the CPU usage
> >> of the threaded interrupt by about 5%. On hardware without support, this
> >> should reduce CPU usage even more since it won't have to split the SPI
> >> transfers each time the interrupt handler is called.
> >>
> >> The update_scan_mode callback hand to be moved to the buffer preenable
> 
> s/hand/had/
> 
> >> callback since the SPI transfer mode can't be changed after
> >> spi_optimize_message() has been called. (The buffer postenable callback
> >> can't be used because it happens after the trigger is enabled, so the
> >> SPI message needs to be optimized before that.)
> >>
> >> The indent of ti_ads7950_read_raw is changed since there is no longer
> >> anything else in the struct to align with since we removed
> >> ti_ads7950_update_scan_mode.
> > 
> > Some of the func() are mentioned w/o parentheses and I got lost which one is
> > which. Also callbacks usually mentioned as .callback() (with a leading dot).
> 
> I didn't put () in the last paragraph because I was talking about the function
> pointer, not the function. I guess I missed update_scan_mode() though.

Then probably spell it as "pointer to func()" ?

> > The second paragraph doesn't tell me clearly if there is a behaviour change
> > from user perspective.
> 
> It is not clear that the difference the user can notice is that there are
> some CPU cycles freed up for other tasks?

He-he :-)

I asked more about possible behaviour changes in ABI (note, that [significant]
delays moved around might affect ABI if some user's program times out due to
that). But I think it's not the case here.

-- 
With Best Regards,
Andy Shevchenko