Re: [PATCH] USB: serial: ch341: fix simulated-break comment

[Johan Hovold <johan@kernel.org>]

On Tue, Jul 07, 2020 at 04:53:22PM +0200, Michael Hanselmann wrote:
> On devices which do not support break signalling a break condition is
> simulated by sending a NUL byte at the lowest possible speed. The break
> condition will be 9 bit periods long (start bit and eight data bits),
> but the transmission itself also includes the stop bit. The safety
> margin of one bit is kept to account for timing differences.
> 
> Signed-off-by: Michael Hanselmann <public@hansmi.ch>
> ---
> 
> Hi Johan
> 
> On 07.07.20 08:19, Johan Hovold wrote:
> > I reread the break-end comment and found it a bit confusing still. The
> > below seems more correct to me. I'm assuming you did not intend to add
> > an additional bit period as margin?
> 
> The additional bit was intentional, but I missed the start bit and was
> off by one. As such your fix indeed addresses the inconsistency between
> the comment and code. Considering the general quality of the ch341
> chips needing the simulation and to account for timing differences I'd
> instead prefer to increase the delay from 10 to 11 bits (1 start, 8 data,
> 1 stop, 1 margin).

Thanks for confirming. I've applied this patch with a slightly modified
commit message:

	https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial.git/commit/?h=usb-next

Johan