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. Just because checkpatch suggests something doesn't mean that it is easy to address the problem. julia > > More clarification on this issue will be helpful. > > On Sun, 29 Mar 2020, 15:17 Julia Lawall, <julia.lawall@xxxxxxxx> wrote: > > > On Sun, 29 Mar 2020, John Wyatt wrote: > > > On Sun, 2020-03-29 at 11:28 +0200, Julia Lawall wrote: > > > > > > On Sun, 29 Mar 2020, John B. Wyatt IV wrote: > > > > > > > Fix style issue with usleep_range being reported as > preferred over > > > > udelay. > > > > > > > > Issue reported by checkpatch. > > > > > > > > Please review. > > > > > > > > As written in Documentation/timers/timers-howto.rst udelay > is the > > > > generally preferred API. hrtimers, as noted in the docs, > may be too > > > > expensive for this short timer. > > > > > > > > Are the docs out of date, or, is this a checkpatch issue? > > > > > > > > Signed-off-by: John B. Wyatt IV <jbwyatt4@xxxxxxxxx> > > > > --- > > > > drivers/staging/fbtft/fb_agm1264k-fl.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/drivers/staging/fbtft/fb_agm1264k-fl.c > > > > b/drivers/staging/fbtft/fb_agm1264k-fl.c > > > > index eeeeec97ad27..019c8cce6bab 100644 > > > > --- a/drivers/staging/fbtft/fb_agm1264k-fl.c > > > > +++ b/drivers/staging/fbtft/fb_agm1264k-fl.c > > > > @@ -85,7 +85,7 @@ static void reset(struct fbtft_par *par) > > > > dev_dbg(par->info->device, "%s()\n", __func__); > > > > > > > > gpiod_set_value(par->gpio.reset, 0); > > > > - udelay(20); > > > > + usleep_range(20, 20); > > > > > > usleep_range should have a range, eg usleep_range(50, > 100);. But it > > > is > > > hard to know a priori what the range should be. So it is > probably > > > better > > > to leave the code alone. > > > > Understood. > > > > With the question I wrote in the commit message: > > > > "As written in Documentation/timers/timers-howto.rst udelay is > the > > generally preferred API. hrtimers, as noted in the docs, may > be too > > expensive for this short timer. > > > > Are the docs out of date, or, is this a checkpatch issue?" > > > > Is usleep_range too expensive for this operation? > > > > Why does checkpatch favor usleep_range while the docs favor > udelay? > > I don't know the answer in detail, but it is quite possible that > checkpatch doesn't pay any attention to the delay argument. > Checkpatch is > a perl script that highlights things that may be of concern. It > is not a > precise static analsis tool. > > As a matter of form, all of your Please review comments should > have been > put below the ---. Currently, if someone had wanted to apply > the patch, > you would make them do extra work to remove this information. > > julia > > > > > > > > > julia > > > > > > > gpiod_set_value(par->gpio.reset, 1); > > > > mdelay(120); > > > > } > > > > -- > > > > 2.25.1 > > > > > > > > -- > > > > You received this message because you are subscribed to > the Google > > > > Groups "outreachy-kernel" group. > > > > To unsubscribe from this group and stop receiving emails > from it, > > > > send an email to > outreachy-kernel+unsubscribe@xxxxxxxxxxxxxxxx. > > > > To view this discussion on the web visit > > > >https://groups.google.com/d/msgid/outreachy-kernel/20200329092204.770405-1- > jbwyatt4%40gmail.com > > > > . > > > > > > > > > > -- > You received this message because you are subscribed to the > Google Groups "outreachy-kernel" group. > To unsubscribe from this group and stop receiving emails from > it, send an email to > outreachy-kernel+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visithttps://groups.google.com/d/msgid/outreachy-kernel/alpine.DEB.2.21.20032911 > 44460.2990%40hadrien. > > >
