Re: Add new ASYNC_SPD_WARP13?

[Grant Edwards <grant.b.edwards@gmail.com>]

On 2011-04-06, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
>> This raises a question I've been wondering about for some time.  While
>> the kernel and the serial driver API support arbitrary baud rates,
>> termios doesn't AFAICT.
>> 
>> How does one use the standard POSIX serial port API to obtain an
>> abritrary baud rate?
>
> The POSIX API is completely broken in this respect. So the kernel
> provides its own interface.
>
>> The only way I can find to get arbitrary baud rates from a user
>> perspective is to use the ASYNC_SPD_xxxx mechanism.
>
> Which is also not POSIX

Right.

> Simple example app:
>  
> http://www.kerneltrap.com/mailarchive/linux-usb/2008/10/2/3484644

Brilliant!

I've been looking for that (off and on) for months.  I knew that the
kernel/driver API supported arbitrary baud rates and that termios
didn't.  So I figured there must be an alternative to SPD_CUST, but
hadn't been able to figure out what it was.

I had found the BSD IOSSIOSPEED ioctl, but hadn't stumbled across the
Linux equivalent.

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