Messages in this thread | | | Subject | Re: [PATCH] Staging: comedi: drivers: comedi_test: Avoid multiple line dereference | From | Ian Abbott <> | Date | Tue, 21 Feb 2017 10:12:57 +0000 |
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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 <thrust73@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.
-- -=( Ian Abbott @ MEV Ltd. E-mail: <abbotti@mev.co.uk> )=- -=( Web: http://www.mev.co.uk/ )=-
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