linux-kernel - Re: [Outreachy kernel] [PATCH] staging: fbtft: Replace udelay with preferred usleep

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Date:   Mon, 30 Mar 2020 15:03:55 -0700
From:   "John B. Wyatt IV" <jbwyatt4@...il.com>
To:     Stefano Brivio <sbrivio@...hat.com>
Cc:     Julia Lawall <julia.lawall@...ia.fr>,
        Soumyajit Deb <debsoumyajit100@...il.com>,
        outreachy-kernel@...glegroups.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Payal Kshirsagar <payal.s.kshirsagar.98@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [Outreachy kernel] [PATCH] staging: fbtft: Replace udelay with
 preferred usleep_range

On Mon, 2020-03-30 at 19:40 +0200, Stefano Brivio wrote:
> On Sun, 29 Mar 2020 12:37:18 +0200 (CEST)
> Julia Lawall <julia.lawall@...ia.fr> wrote:
> 
> > On Sun, 29 Mar 2020, Soumyajit Deb wrote:
> > 
> > > I had the same doubt the other day about the replacement of
> > > udelay() with
> > > usleep_range(). The corresponding range for the single argument
> > > value of
> > > udelay() is quite confusing as I couldn't decide the range. But
> > > as much as I
> > > noticed checkpatch.pl gives warning for replacing udelay() with
> > > usleep_range() by checking the argument value of udelay(). In the
> > > documentation, it is written udelay() should be used for a sleep
> > > time of at
> > > most 10 microseconds but between 10 microseconds and 20
> > > milliseconds,
> > > usleep_range() should be used. 
> > > I think the range is code specific and will depend on what range
> > > is
> > > acceptable and doesn't break the code.
> > >  Please correct me if I am wrong.  
> > 
> > The range depends on the associated hardware.
> 
> John, by the way, here you could have checked the datasheet of this
> LCD
> controller. It's a pair of those:
> 	https://www.sparkfun.com/datasheets/LCD/ks0108b.pdf
> 

No I have not. This datasheet is a little over my head honestly.

What would you recommend to get familiar with datasheets like this?