[En-Nut-Discussion] Problem with STM32 pin configuration

Ole Reinhardt ole.reinhardt at embedded-it.de
Wed Oct 7 00:01:54 CEST 2015

Hi Uwe,

Thanks for the fix!

For me the SPI now works fine and the connected MX25 dataflash can be
mounted with UFLASH.

I just committed the Macronix dataflash support to the SVN.

Thanks again for your help,


Am 06.10.2015 um 11:46 schrieb Uwe Bonnes:
>>>>>> "Ole" == Ole Reinhardt <ole.reinhardt at embedded-it.de> writes:
>     Ole> Hi Uwe, there is a problem with your new pin configuration scheme,
>     Ole> which you committed a few days ago, which breaks several drivers.
>     Ole> The problem is, that the GCC preprocessor does not know anything
>     Ole> about types. But in several places, a preprocessor comparison like
>     Ole> #if (SPI_CS0 != PIN_NONE)
>     Ole> is used, where PIN_NONE is of the enum type nutgpio_t.
>     Ole> The above comparison is always true, as the preprocessor takes
>     Ole> SPI_CS0 and PIN_NONE as identifiers, not as macros. These are then
>     Ole> both replaced by 0. So finally the comparison is always true.
>     Ole> This kind of preprocessor comparisons are at least used in
>     Ole> arch/cm3/dev/stm/stm32_spi.c arch/cm3/dev/stm/stm32_emac.c
>     Ole> but perhaps ins several more.
>     Ole> See also https://gcc.gnu.org/onlinedocs/gcc-3.0.2/cpp_4.html#SEC38
>     Ole> for a detailed explanation.
>     Ole> Could you please have a look at it? Unfortunately I do not have an
>     Ole> idea for an elegant solution.
> Thanks for the hint. Argh, I stumbled on that problem before with the vendor
> headers :-(
> There are only the (5) places you pointed out where a compile time test for
> unused pins is done. With your solution, every of the about 200 pins needs a
> corresponding #define. Also pin name would vary when used for compile time
> vs. run-time usage. Let us consider if that is needed.
> The test in stm32_emac.s can easily be rewritten as
>     if (Stm32GpioConfigSet(EMAC_PHY_CLOCK_MCO, GPIO_CFG_PERIPHAL |
>         /* Output HSE clock (25MHz) on MCO pin (PA8) to clock the PHY */
>     }
> without defines and with very low runtime impact.
> The 4 tests for unconnected pins in stm32_spi.h are harder to work around,
> as long as the SPI driver uses per-device files.
> In the long run, I tend to rewrite the spi-driver as one driver as
> stm32_i2cbus_v2.c already is. This will also require run-time decision on
> the pins used and remove the defines.
> On the short run, the setup seems broken anyhow:
> #if (SPI_CS0 != 0)
> #warning bla
> #define SPIBUS_SCK_PORT     (uint32_t)(stm32_port_nr2gpio[SPI_CS0  >> 8])
> #define SPIBUS_SCK_PIN      (SPI_CS0 & 0xf)
> ...
> This mixes SCK with CS0. Argh :-(
> Again, SPIBUS_CSx_INIT(x) can be used without compile-time defines with low
> run-time impact. For SPIBUS_CSx_SET and For SPIBUS_CSx_CLR I will probably
> introduce "void Stm32GpioSet(nutgpio_t gpio, int value)" as exported
> function. The function would return without setting anything if called with
> PIN_NONE. The run-time effect on  Stm32SpiChipSelect() should be barable.
> I will try to fix and test.
> B.t.w. I in spibus.h, don't see a place to store private hardware data like
> in i2cbus.h:
>     /*! \brief Private data of the hardware specific implementation. */
>     void *bus_icb;
> Do I miss something? Otherwise, can we extend struct _NUTSPIBUS  for
>     void *bus_icb;
> at the end, without causing damage to others?
> Any other Ideas?
> Bye

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