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Date: Wed, 1 Mar 2017 16:42:51 +0530
From: Aishwarya Pant <aishpant@gmail.com>
To: Julia Lawall <julia.lawall@lip6.fr>
Cc: Lidza Louina <lidza.louina@gmail.com>,
	Mark Hounschell <markh@compro.net>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	outreachy-kernel@googlegroups.com
Subject: Re: [Outreachy kernel] [PATCH v3] staging: dgnc: replace
 usleep_range with udelay
Message-ID: <20170301111251.GA2160@aishwarya>
References: <20170301103315.GA4448@aishwarya>
 <alpine.DEB.2.20.1703011154490.3941@hadrien>
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On Wed, Mar 01, 2017 at 11:56:18AM +0100, Julia Lawall wrote:
> 
> 
> On Wed, 1 Mar 2017, Aishwarya Pant wrote:
> 
> > udelay is impelmented using a busy-wait loop and consumes CPU cycles
> > while usleep_range is implemented using interrupts.cls_flush_uart_write()
> > is called after a channel lock is acquired i.e. an atomic context.
> > Hence delay in this method should use udelay instead of usleep_range.
> >
> > Signed-off-by: Aishwarya Pant <aishpant@gmail.com>
> >
> > ---
> > Changes in v3:
> > 	- Add a comment in code udelay to ignore checkpatch warning
> > Changes in v2:
> > 	- Edit commit message to explain why udelay should be used
> >
> >  drivers/staging/dgnc/dgnc_cls.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/staging/dgnc/dgnc_cls.c b/drivers/staging/dgnc/dgnc_cls.c
> > index 28a3e16..ec190e5 100644
> > --- a/drivers/staging/dgnc/dgnc_cls.c
> > +++ b/drivers/staging/dgnc/dgnc_cls.c
> > @@ -609,7 +609,11 @@ static void cls_flush_uart_write(struct channel_t *ch)
> >
> >  	writeb((UART_FCR_ENABLE_FIFO | UART_FCR_CLEAR_XMIT),
> >  	       &ch->ch_cls_uart->isr_fcr);
> > -	usleep_range(10, 20);
> > +
> > +	/* Ignore checkpatch warning to replace udelay by usleep_range
> > +	 * as this function is called under an atomic context
> > +	 */
> > +	udelay(10);
> 
> I think this doesn't follow the proper block comment format?
>
 
I looked through the coding style docs and found the correct format 
for multi-line comments-
/*
 * Some comments spanning over
 * multiple lines
 */

What is convention for single line comments?

> Anyway, perhaps something like "called in atomic context so usleep_range
> not used" would be sufficient.
> 
> julia
> 
> >
> >  	ch->ch_flags |= (CH_TX_FIFO_EMPTY | CH_TX_FIFO_LWM);
> >  }
> > --
> > 2.7.4
> >
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