Re: [RFC PATCH 0/3] UART slave device bus

Sebastian Reichel
2016-08-22T23:58:28Z

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Hi,

On Mon, Aug 22, 2016 at 11:54:14PM +0100, One Thousand Gnomes wrote:
> On Tue, 23 Aug 2016 00:00:17 +0200
> Pavel Machek <pavel@ucw.cz> wrote:
>
> > On Mon 2016-08-22 22:32:23, One Thousand Gnomes wrote:
> > > > why would we even have it create a /dev/ttyX for these devices in the first place. Lets just not create an uevent for it and lets not create a dev_t for it.
> > >
> > > Because if you don't it's a regression. It's not permissible to break
> > > existing userspace.
> >
> > Well... it would be good to do the right thing, at least in the places
> > where we can.
> >
> > Yes, renumbering people's serials is bad, OTOH for new platforms it
> > would be nice not to expose ttyS15 which can only return -EBUSY.
>
> That would still be a regression. Not everyone even uses the kernel
> bluetooth stack. It would only return EBUSY if you had done an "up"
> on it via the direct bluetooth stack.

So it returns EBUSY when uart-bus is used. Since uart-bus is about
hardwired devices that's basically always.

Also I wonder how relevant your "I want to handle all UART stuff out of
kernel" scenario is for uart-bus, which is about in-kernel UART
drivers.

-- Sebastian

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