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

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Date:   Wed, 7 Dec 2016 12:01:52 +0000
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Lee Jones <lee.jones@...aro.org>
Cc:     robh+dt@...nel.org, Mark Rutland <mark.rutland@....com>,
        alexandre.torgue@...com, devicetree@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-pwm@...r.kernel.org, Jonathan Cameron <jic23@...nel.org>,
        knaack.h@....de, Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Fabrice Gasnier <fabrice.gasnier@...com>,
        Gerald Baeza <gerald.baeza@...com>,
        Arnaud Pouliquen <arnaud.pouliquen@...com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Linaro Kernel Mailman List <linaro-kernel@...ts.linaro.org>,
        Benjamin Gaignard <benjamin.gaignard@...com>
Subject: Re: [PATCH v4 6/7] IIO: add STM32 timer trigger driver

On 07/12/16 11:00, Benjamin Gaignard wrote:
> 2016-12-07 11:50 GMT+01:00 Lee Jones <lee.jones@...aro.org>:
>> 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.