On Mon, Feb 20, 2017 at 05:36:52PM +0000, Ian Abbott wrote:
> On 20/02/17 16:02, Cheah Kok Cheong wrote:
> >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 <thrus...@gmail.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 ]
> 
> It will work, but you could just use a pointer variable set to
> &devpriv->ao_loopbacks[chan] and pass that to comedi_buf_read_samples().
> 

Thanks for the suggestion. I tried below snippet 1 with the shortest pointer
name but 80 characters is exceeded. The declaration and initialisation
will have to be splitted. Will this be acceptable or am I doing it wrong
again?

Sorry for the trouble.

Snippet 1:
[ Snip ]

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

                                if (!comedi_buf_read_samples(s, p, 1)) {
                                        /* unexpected underrun! (cancelled?) */
                                        async->events |= COMEDI_CB_OVERFLOW;
                                        goto underrun;
                                }
                        }
                        /* advance time of last scan */

[ Snip ]

Snippet 2:
[ Snip ]

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

                                pd = &devpriv->ao_loopbacks[chan];

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

[ Snip ]

Thks.
Brgds,
CheahKC
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