Re: [PATCH v4 6/7] IIO: add STM32 timer trigger driver

[Daniel Thompson <daniel.thompson@xxxxxxxxxx>]

On 07/12/16 11:00, Benjamin Gaignard wrote:
> 2016-12-07 11:50 GMT+01:00 Lee Jones <lee.jones@xxxxxxxxxx>:
> > On Tue, 06 Dec 2016, Benjamin Gaignard wrote:
> >
> > > [snip]
> > > > > +
> > > > > +static const char * const triggers0[] = {
> > > > > +     TIM1_TRGO, TIM1_CH1, TIM1_CH2, TIM1_CH3, TIM1_CH4, NULL,
> > > > > +};
> > > > > +
> > > > > +static const char * const triggers1[] = {
> > > > > +     TIM2_TRGO, TIM2_CH1, TIM2_CH2, TIM2_CH3, TIM2_CH4, NULL,
> > > > > +};
> > > > > +
> > > > > +static const char * const triggers2[] = {
> > > > > +     TIM3_TRGO, TIM3_CH1, TIM3_CH2, TIM3_CH3, TIM3_CH4, NULL,
> > > > > +};
> > > > > +
> > > > > +static const char * const triggers3[] = {
> > > > > +     TIM4_TRGO, TIM4_CH1, TIM4_CH2, TIM4_CH3, TIM4_CH4, NULL,
> > > > > +};
> > > > > +
> > > > > +static const char * const triggers4[] = {
> > > > > +     TIM5_TRGO, TIM5_CH1, TIM5_CH2, TIM5_CH3, TIM5_CH4, NULL,
> > > > > +};
> > > > > +
> > > > > +static const char * const triggers5[] = {
> > > > > +     TIM6_TRGO, NULL,
> > > > > +};
> > > > > +
> > > > > +static const char * const triggers6[] = {
> > > > > +     TIM7_TRGO, NULL,
> > > > > +};
> > > > > +
> > > > > +static const char * const triggers7[] = {
> > > > > +     TIM8_TRGO, TIM8_CH1, TIM8_CH2, TIM8_CH3, TIM8_CH4, NULL,
> > > > > +};
> > > > > +
> > > > > +static const char * const triggers8[] = {
> > > > > +     TIM9_TRGO, TIM9_CH1, TIM9_CH2, NULL,
> > > > > +};
> > > > > +
> > > > > +static const char * const triggers9[] = {
> > > > > +     TIM12_TRGO, TIM12_CH1, TIM12_CH2, NULL,
> > > > > +};
> > > > > +
> > > > > +static const void *triggers_table[] = {
> > > > > +     triggers0,
> > > > > +     triggers1,
> > > > > +     triggers2,
> > > > > +     triggers3,
> > > > > +     triggers4,
> > > > > +     triggers5,
> > > > > +     triggers6,
> > > > > +     triggers7,
> > > > > +     triggers8,
> > > > > +     triggers9,
> > > > > +};
> > > >
> > > > What about:
> > > >
> > > > static const char * const triggers[][] = {
> > > >         { TIM1_TRGO, TIM1_CH1, TIM1_CH2, TIM1_CH3, TIM1_CH4, NULL },
> > > >         { TIM2_TRGO, TIM2_CH1, TIM2_CH2, TIM2_CH3, TIM2_CH4, NULL },
> > > >         { TIM3_TRGO, TIM3_CH1, TIM3_CH2, TIM3_CH3, TIM3_CH4, NULL },
> > > >         { TIM4_TRGO, TIM4_CH1, TIM4_CH2, TIM4_CH3, TIM4_CH4, NULL },
> > > >         { TIM5_TRGO, TIM5_CH1, TIM5_CH2, TIM5_CH3, TIM5_CH4, NULL },
> > > >         { TIM6_TRGO, NULL },
> > > >         { TIM7_TRGO, NULL },
> > > >         { TIM8_TRGO, TIM8_CH1, TIM8_CH2, TIM8_CH3, TIM8_CH4, NULL },
> > > >         { TIM9_TRGO, TIM9_CH1, TIM9_CH2, NULL },
> > > >         { TIM12_TRGO, TIM12_CH1, TIM12_CH2, NULL }
> > > > };
> > >
> > > I can't because the second dimension of the array isn't fix.
> > > I could have between 2 and 6 elements per row... to create a dual dimension
> > > array I would have to add NULL entries like that:
> > >
> > > #define MAX_TRIGGERS 6
> > >
> > > static const void *triggers_table[][MAX_TRIGGERS] = {
> > > { TIM1_TRGO, TIM1_CH1, TIM1_CH2, TIM1_CH3, TIM1_CH4, NULL,},
> > > { TIM2_TRGO, TIM2_CH1, TIM2_CH2, TIM2_CH3, TIM2_CH4, NULL,},
> > > { TIM3_TRGO, TIM3_CH1, TIM3_CH2, TIM3_CH3, TIM3_CH4, NULL,},
> > > { TIM4_TRGO, TIM4_CH1, TIM4_CH2, TIM4_CH3, TIM4_CH4, NULL,},
> > > { TIM5_TRGO, TIM5_CH1, TIM5_CH2, TIM5_CH3, TIM5_CH4, NULL,},
> > > { TIM6_TRGO, NULL,     NULL,     NULL,     NULL,     NULL,},
> > > { TIM7_TRGO, NULL,     NULL,     NULL,     NULL,     NULL,},
> > > { TIM8_TRGO, TIM8_CH1, TIM8_CH2, TIM8_CH3, TIM8_CH4, NULL,},
> > > { TIM9_TRGO, TIM9_CH1, TIM9_CH2, NULL,     NULL,     NULL,},
> > > { TIM12_TRGO, TIM12_CH1, TIM12_CH2, NULL,  NULL,     NULL,},
> > > };
> >
> > It was just an idea, not a tested implementation.
> >
> > I don't understand why you have to pad with NULLs, but either way, it
> > looks much better than before and saves lots of lines of code.
>
> I have tested it this morning and it works fine so I will include it in v5.
> I use NULL as limit when iterate in the table and for table padding too.

If the initializer is shorter than the array then the array will be 
implicitly zero/NULL padded. I don't think there is any need to type out 
all the NULLs (not even at -Wall).


Daniel.

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