Re: [PATCH v3 0/3] IR driver for USB-UIRT device

[Sean Young <sean@mess.org>]

On Thu, May 20, 2021 at 03:31:34PM +0200, Johan Hovold wrote:
> On Mon, May 17, 2021 at 11:35:22AM +0100, Sean Young wrote:
> > On Mon, May 17, 2021 at 11:30:39AM +0200, Johan Hovold wrote:
> > > On Sat, May 15, 2021 at 10:22:26AM +0100, Sean Young wrote:
> > > > The other nice thing is that IR TX feeds data from an urb interrupt handler,
> > > > so you don't need to rely userspace being scheduled quickly enough to feed
> > > > more data before the device runs out.
> > > 
> > > The tty layer and tty drivers provide write buffering so that need not
> > > be an issue.
> >  
> > Ok. I don't know what the size of the write buffer is or what the maximum
> > TX size is; the IR device supports infinite streaming.
> 
> Our tty drivers typically have at least a 4k buffer for transmission.
> Surely that should be enough for a remote control but perhaps there are
> other more demanding applications?

That's more than enough. The most demanding consumer IR I know of, is
an air conditioner which encodes temperature and a few others things. That's
a maximum of 439 pulse/spaces which should into 1k.
> 
> > > Thanks for that pointer. Judging from a quick look, the new driver
> > > appears to based on this one. By abstracting the serial interface bits
> > > in a generic RC serdev/ldisc driver you may be able reuse more code,
> > > even if I'm not in a position to judge how much of the IR protocol bits
> > > that can be shared.
> > 
> > Yes, I agree. Once hotplugging is in place. If you have patches for that,
> > please CC me and I can see if will work for IR drivers.
> 
> Let's hope someone steps up to fund that work then.

I'm just a volunteer. I've literally never heard anything about kernel work
being funded by anyone.

Would you mind giving a brief summary what is needed to implement hotplugging
for serdev? I get the impression it's not a lot of work, but I'm probably
missing something obvious.


Sean