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Message-ID: <YdRSnxqIJf1C14+x@smile.fi.intel.com>
Date: Tue, 4 Jan 2022 15:58:55 +0200
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Uwe Kleine-König
<u.kleine-koenig@...gutronix.de>
Cc: vishakha.joshi@...el.com, thierry.reding@...il.com,
lee.jones@...aro.org, linux-pwm@...r.kernel.org,
linux-kernel@...r.kernel.org, jarkko.nikula@...ux.intel.com,
vijayakannan.ayyathurai@...el.com, bala.senthil@...el.com,
tamal.saha@...el.com, lakshmi.bai.raja.subramanian@...el.com
Subject: Re: [PATCH v1 1/2] pwm: Add count to sysfs for Intel PWM driver
On Mon, Jan 03, 2022 at 01:14:54PM +0100, Uwe Kleine-König wrote:
> On Mon, Jan 03, 2022 at 01:46:09PM +0530, vishakha.joshi@...el.com wrote:
> > From: Vishakha Joshi <vishakha.joshi@...el.com>
...
> > struct pwm_state {
> > u64 period;
> > u64 duty_cycle;
> > + u32 count;
> > enum pwm_polarity polarity;
> > bool enabled;
> > bool usage_power;
>
> This needs more documentation about what the semantic should be. E.g.
> what should .get_state return?
Good point. I guess ideally we should return the amount of the periods we still
need to produce, but I'm not sure if it can be done cleanly.
It would probably require a timer to be run in parallel, hence almost full
software implementation of the feature. (This answers the second concern)
> Also I doubt this is a good idea given that most controllers cannot
> implement it.
>
> If we really want to support a count, I request that all drivers that
> don't support it get updated to refuse a request with count != 0.
Hmm... Not sure it worth it, perhaps taking into account above the -1
(in unsigned type) returned on ->get_state() can suffice as not supporting
feature?
--
With Best Regards,
Andy Shevchenko
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