Re: Spliting u16, u32 to u8 array

[Lars-Peter Clausen <lars@metafoo.de>]

On 08/06/2015 12:42 PM, Peter Meerwald wrote:
> Hello,
> 
>> I am sure at least some of you were faced to split a u16 or u32 value
>> in u8 array without being affected by host endianness. My search
>> turned empty for a standardized function for this task, but this seems
>> quite improbable. My task is to send 16 bit LE data through i2c.
>>
>> I am looking for something like:
>> static void u16_to_u8_array(u16 value, u8 *array)
>> {
>>         *array = cpu_to_le16(value) >> 8;
>>         *(++array) = (u8) cpu_to_le16(value);
>> }
> 
> how about
> 
> static void u16_to_le16_array(u16 value, __le16 *array)
> {
> 	*array++ = cpu_to_le16(value);
> }
> 
> and calling it with a cast if need be, such as
> 
> char *u8array;
> u16_to_le16_array(123, (__le16 *) u8array)
> 
> an issue could be alignment of the u8array

There is put_unaligned_le16() and friends for this situation where the
target buffer is just a generic bytestream. This is architecture optimized,
so if the architecture supports unaligned access it will just do a store, if
it doesn't it will split the operation into multiple stores.

> 
> I'd try to avoid u8 altogether and work with le16 as a datatype

That seems to be the best solution in this case.