On 07.11.2010 15:46, erik quanstrom wrote:
>> writearr should point to a one-member const unsigned char array, and the
>> zeroth element of that array has the value JEDEC_WREN.
>>
> =
> it's not clear to me that c99 allows one to declare an unnamed array
> and assign a pointer to it in this way except if the array is a char* or
> wchar_t*.
>
> i think the cleanest approach to solving your problem is
> to define writeattr as an array, not a uchar*.
>
The big problem with defining it as an array inside struct spicmd is
that writearr has variable length. writearr is a command sent to a SPI
chip by a SPI controller. writearr can have any length of 1-1056 bytes.
There's also an analogous readarr in struct spi_command (not mentioned
in the example to keep it brief) and that one can have any length
between 0 and 16777217 (2^24+1) bytes. One variable-length array at the
end of a struct is possible, but an array of structs with a variable
length array in the struct won't work since you can't compute the offset
of individual members of the outer arrray.
The only solution I can see is this:
#define JEDEC_WREN 0x06
#define JEDEC_SE 0x20
struct spi_command {
const unsigned char *writearr;
};
int main(int argc, char *argv[])
{
const unsigned char writearr_helper1[] = { JEDEC_WREN };
const unsigned char writearr_helper2[] = { JEDEC_SE, 0x01, 0x23, 0x45 };
struct spi_command cmds[] = {
{
.writearr = writearr_helper1,
},{
.writearr = writearr_helper2,
}};
/* ... */
}
That solution wastes variables and is generally pretty ugly.
I still hope we can find a better solution.
Regards,
Carl-Daniel
--
http://www.hailfinger.org/
