linux-kernel - Re: [PATCH v2 2/2] mfd: intel_quark_i2c

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Date:   Wed, 24 Mar 2021 13:07:23 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] mfd: intel_quark_i2c_gpio: enable MSI interrupt

On Wed, 24 Mar 2021, Andy Shevchenko wrote:

> On Wed, Mar 24, 2021 at 11:50:33AM +0000, Lee Jones wrote:
> > On Wed, 24 Mar 2021, Andy Shevchenko wrote:
> > 
> > > On Wed, Mar 24, 2021 at 10:47:29AM +0000, Lee Jones wrote:
> > > > On Wed, 24 Mar 2021, Andy Shevchenko wrote:
> > > > > On Wed, Mar 24, 2021 at 10:29:31AM +0000, Lee Jones wrote:
> > > > > > On Tue, 23 Mar 2021, Andy Shevchenko wrote:
> > > 
> > > ...
> > > 
> > > > Also, past acceptance does not guarantee ideal/correct usage.
> > > 
> > > In this case it's hardly can be misused. But I heard you.
> > > 
> > > ...
> > > 
> > > > > The semantic is min-max range and having two defines (*) here for these seems
> > > > > to me as an utter overkill.
> > > > > 
> > > > > Of course, if you insist I may do it.
> > > > > 
> > > > > *) since value is the same, we might have one definition, but it will be even
> > > > >    more confusion to have it as a min and max at the same time.
> > > > 
> > > > It's just tricky to decypher for people who do not know the API, which
> > > > is most people, myself included.  For APIs like usleep_range() et al.,
> > > > obviously this makes no sense at all.
> > > 
> > > Seem like you are insisting. Okay, I will define them. What do you prefer one
> > > or two definitions?
> > 
> > Actually I'm not.  I'm just trying to get my head around where the
> > data comes from and what the values actually mean.
> > 
> > > ...
> > > 
> > > > What defines a vector?
> > > 
> > > The combination is solely of the driver-hardware. Driver explicitly tells that
> > > how many vectors it may consume (taking into account the range asked) and API
> > > returns amount given or an error.
> > 
> > So, where does the information actually come from?
> > 
> > Information that comes from a datasheet is usually defined.
> > 
> > Information that comes from the F/W is usually read and popped into a
> > variable.
> 
> It's a two way road:
> a) driver states that it needs only 1 vector and it's enough to it
> b) hardware must provide at least 1 vector to be served by this driver.
> 
> Look again into grepped output. Most of drivers that define it as an variable
> may dynamically adapt to the different amount of IRQ vectors. When it's static,
> usually drivers just hard code those values.
> 
> I'm really don't see a point to define them _in this driver_.

That's fine.  I just felt like I had to ask.

Would you consider a comment that lets people unfamiliar with the API
what the values mean?

Something to the tune of:

  "This driver requests 1 (and only 1) IRQ vector"

-- 
Lee Jones [李琼斯]
Senior Technical Lead - Developer Services
Linaro.org │ Open source software for Arm SoCs
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