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Re: [RFC] termios: non-standard baudrates are not handled properly on Linux-systems (BZ#10339)



On 03/10/2018 19:13, H. Peter Anvin wrote:
> On 10/03/18 15:01, Paul Eggert wrote:
>> On 10/3/18 12:47 PM, Adhemerval Zanella wrote:
>>> Hans Peter Anvin is advocating for second options [2], with the new
>>> API as:
>>>
>>>   -- Function: speed_t cfgetispeedbps (struct termios *TERMIOS-P)
>>>       This function returns the input line speed stored in the
>>>       structure `*TERMIOS-P' as a number of bits per second.
>>
>>
>> speed_t is unsigned int. Is that enough for all devices likely in the
>> reasonably-near future? I see stories about Arduino serial ports running
>> at multiple Mb/s, and although that fits it's getting uncomfortably
>> close to UINT_MAX. USB 3.0 can in theory do 5 Gb/s, which would exceed
>> 'unsigned int' range, and USB 3.1 and 3.2 are even faster.
>>
> 
> speed_t might be 16 bits on some (non-glibc) platforms as far as we know.
> 
> 	-hpa
> 

At least for Linux, it seems speed_t is defined as unsigned int for all
architectures.  It is possible to define the new baud speed abi to take
a new type with larger range, but we will need to describe its interaction
with speed_t and it would add more complexity in glibc application without
much gain.


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