linux-kernel - Re: [PATCH] Staging: comedi: drivers: comedi

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Message-ID: <20170220160205.GA4017@linux-Precision-WorkStation-T5500>
Date:   Tue, 21 Feb 2017 00:02:05 +0800
From:   Cheah Kok Cheong <thrust73@...il.com>
To:     Ian Abbott <abbotti@....co.uk>
Cc:     hsweeten@...ionengravers.com, gregkh@...uxfoundation.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Staging: comedi: drivers: comedi_test: Avoid multiple
 line dereference

On Mon, Feb 20, 2017 at 10:03:39AM +0000, Ian Abbott wrote:
> On 20/02/17 08:28, Cheah Kok Cheong wrote:
> >Fix checkpatch warning "Avoid multiple line dereference"
> >using a local variable to avoid line wrap.
> >
> >Signed-off-by: Cheah Kok Cheong <thrust73@...il.com>
> >---
> > drivers/staging/comedi/drivers/comedi_test.c | 6 ++----
> > 1 file changed, 2 insertions(+), 4 deletions(-)
> >
> >diff --git a/drivers/staging/comedi/drivers/comedi_test.c b/drivers/staging/comedi/drivers/comedi_test.c
> >index 2a063f0..fde83e0 100644
> >--- a/drivers/staging/comedi/drivers/comedi_test.c
> >+++ b/drivers/staging/comedi/drivers/comedi_test.c
> >@@ -480,11 +480,9 @@ static void waveform_ao_timer(unsigned long arg)
> > 			/* output the last scan */
> > 			for (i = 0; i < cmd->scan_end_arg; i++) {
> > 				unsigned int chan = CR_CHAN(cmd->chanlist[i]);
> >+				unsigned short d = devpriv->ao_loopbacks[chan];
> >
> >-				if (comedi_buf_read_samples(s,
> >-							    &devpriv->
> >-							     ao_loopbacks[chan],
> >-							    1) == 0) {
> >+				if (!comedi_buf_read_samples(s, &d, 1)) {
> > 					/* unexpected underrun! (cancelled?) */
> > 					async->events |= COMEDI_CB_OVERFLOW;
> > 					goto underrun;
> >
> 
> NAK.  This leaves devpriv->ao_loopbacks[chan] unchanged.
> 

Thanks for pointing this out. In that case will assigning the variable to
devpriv->ao_loopbacks[chan] be acceptable? Please review below snippet.

Otherwise I'll just drop the variable and adjust the lines to avoid
checkpatch warning.

Sorry for the inconvenience caused.

[ Snip ]

			/* output the last scan */
			for (i = 0; i < cmd->scan_end_arg; i++) {
				unsigned int chan = CR_CHAN(cmd->chanlist[i]);
				unsigned short data;

				if (!comedi_buf_read_samples(s, &data, 1)) {
					/* unexpected underrun! (cancelled?) */
					async->events |= COMEDI_CB_OVERFLOW;
					goto underrun;
				}

				devpriv->ao_loopbacks[chan] = data;
			}
			/* advance time of last scan */

[ Snip ]

Thks.
Brgds,
CheahKC