lkml.org 
[lkml]   [2017]   [Feb]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] Staging: comedi: drivers: comedi_test: Avoid multiple line dereference
From
Date
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/ )=-

\
 
 \ /
  Last update: 2017-02-21 11:14    [W:0.199 / U:0.128 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site