On Feb 21 '17 10:12, Ian Abbott wrote:
> On 21/02/2017 09:33, Cheah Kok Cheong wrote:
> > 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 ]
>
> Snippet 2 looks fine. Alternatives are to modify Snippet 1 to split the
> initialization of the pointer variable after the '=', or to shorten the the
> name of the 'chan' variable.
Another option could be using the typedefs from include/linux/types.h,
e.g. ushort. However, this might require changing other declarations as
well to keep consistency.
> --
> -=( Ian Abbott @ MEV Ltd. E-mail: <abbo...@mev.co.uk> )=-
> -=( Web: http://www.mev.co.uk/ )=-
