From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Marcel Holtmann <marcel@holtmann.org>
Cc: Rob Herring <robh@kernel.org>, Jiri Slaby <jslaby@suse.com>,
Sebastian Reichel <sre@kernel.org>, Pavel Machek <pavel@ucw.cz>,
Peter Hurley <peter@hurleysoftware.com>,
NeilBrown <neil@brown.name>,
"Dr . H . Nikolaus Schaller" <hns@goldelico.com>,
Arnd Bergmann <arnd@arndb.de>,
Linus Walleij <linus.walleij@linaro.org>,
"open list:BLUETOOTH DRIVERS" <linux-bluetooth@vger.kernel.org>,
linux-serial@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Loic Poulain <loic.poulain@intel.com>
Subject: Re: [RFC PATCH 0/3] UART slave device bus
Date: Thu, 18 Aug 2016 12:53:33 +0200 [thread overview]
Message-ID: <20160818105333.GA7031@kroah.com> (raw)
In-Reply-To: <FC1D6B2F-E06B-4D8F-90BA-4D6F20F2507A@holtmann.org>
On Thu, Aug 18, 2016 at 12:30:32PM +0200, Marcel Holtmann wrote:
> Hi Greg,
>
> >> Currently, devices attached via a UART are not well supported in the
> >> kernel. The problem is the device support is done in tty line disciplines,
> >> various platform drivers to handle some sideband, and in userspace with
> >> utilities such as hciattach.
> >>
> >> There have been several attempts to improve support, but they suffer from
> >> still being tied into the tty layer and/or abusing the platform bus. This
> >> is a prototype to show creating a proper UART bus for UART devices. It is
> >> tied into the serial core (really struct uart_port) below the tty layer
> >> in order to use existing serial drivers.
> >>
> >> This is functional with minimal testing using the loopback driver and
> >> pl011 (w/o DMA) UART under QEMU (modified to add a DT node for the slave
> >> device). It still needs lots of work and polish.
> >>
> >> TODOs:
> >> - Figure out the port locking. mutex plus spinlock plus refcounting? I'm
> >> hoping all that complexity is from the tty layer and not needed here.
> >
> > It should be.
> >
> >> - Split out the controller for uart_ports into separate driver. Do we see
> >> a need for controller drivers that are not standard serial drivers?
> >
> > What do you mean by "controller" drivers here? I didn't understand them
> > in the code.
> >
> >> - Implement/test the removal paths
> >> - Fix the receive callbacks for more than character at a time (i.e. DMA)
> >> - Need better receive buffering than just a simple circular buffer or
> >> perhaps a different receive interface (e.g. direct to client buffer)?
> >
> > Why? Is the code as-is slow?
> >
> >> - Test with other UART drivers
> >> - Convert a real driver/line discipline over to UART bus.
> >
> > That's going to be the real test, I recommend trying that as soon as
> > possible as it will show where the real pain points are :)
>
> maybe we can get the Intel LnP driver ported over and see how that one
> works out. It is one of the more complex ones when it comes to
> bootloader and firmware loading. Maybe Loic can take a stab at this.
> We would then also see how we can map the ACPI tables into a driver.
Yes, I was going to complain about the OF-only bent of this patch, but I
figured it would get fixed up once Rob started to use a "real" machine
for his testing of this code :)
> >> Before I spend more time on this, I'm looking mainly for feedback on the
> >> general direction and structure (the interface with the existing serial
> >> drivers in particular).
> >
> > Yes, I like the idea (minor nit, you still have SPMI in a lot of places
> > instead of UART), so I recommend keeping going with it.
> >
> >> drivers/uart/Kconfig | 17 ++
> >> drivers/uart/Makefile | 3 +
> >> drivers/uart/core.c | 458 +++++++++++++++++++++++++++++++++++++++
> >> drivers/uart/loopback.c | 72 ++++++
> >
> > Why not just put this in drivers/tty/uart/ ?
>
> Is it really then a TTY at all. Would be the UART become the basic
> core for a TTY?
Hm, interesting idea. Not for all TTYs of course, but for those that
are on UART devices, maybe? How would a usb-serial device fit into that
picture?
> Having tty/uart/ seems a bit backward. Then again, it is just a
> directory name ;)
And as we know, naming is hard :)
thanks,
greg k-h
next prev parent reply other threads:[~2016-08-18 10:53 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-18 1:14 [RFC PATCH 0/3] UART slave device bus Rob Herring
2016-08-18 1:14 ` [RFC PATCH 1/3] uart bus: Introduce new bus for UART slave devices Rob Herring
2016-08-18 1:14 ` [RFC PATCH 2/3] tty: serial_core: make tty_struct optional Rob Herring
2016-08-18 10:50 ` Pavel Machek
2016-08-18 1:14 ` [RFC PATCH 3/3] tty: serial_core: add uart controller registration Rob Herring
2016-08-18 10:22 ` [RFC PATCH 0/3] UART slave device bus Greg Kroah-Hartman
2016-08-18 10:30 ` Marcel Holtmann
2016-08-18 10:53 ` Greg Kroah-Hartman [this message]
2016-08-18 13:53 ` Rob Herring
2016-08-18 13:15 ` Rob Herring
[not found] ` <20160818160449.328b2eec@lxorguk.ukuu.org.uk>
2016-08-18 18:33 ` Rob Herring
2016-08-19 11:03 ` One Thousand Gnomes
2016-08-25 16:40 ` Rob Herring
2016-08-26 13:12 ` One Thousand Gnomes
2016-08-18 10:39 ` H. Nikolaus Schaller
2016-08-18 10:47 ` Pavel Machek
2016-08-18 10:54 ` H. Nikolaus Schaller
2016-08-18 10:57 ` Greg Kroah-Hartman
2016-08-18 11:14 ` H. Nikolaus Schaller
2016-08-18 14:40 ` One Thousand Gnomes
2016-08-18 11:27 ` H. Nikolaus Schaller
2016-08-18 10:49 ` Marcel Holtmann
2016-08-18 10:55 ` Greg Kroah-Hartman
2016-08-18 11:01 ` Marcel Holtmann
2016-08-18 11:24 ` Greg Kroah-Hartman
2016-08-18 11:42 ` Pavel Machek
2016-08-18 11:51 ` Marcel Holtmann
2016-08-18 11:10 ` Pavel Machek
2016-08-18 11:18 ` H. Nikolaus Schaller
2016-08-18 11:49 ` Marcel Holtmann
2016-08-18 12:16 ` H. Nikolaus Schaller
2016-08-18 11:47 ` Marcel Holtmann
2016-08-18 13:01 ` Pavel Machek
2016-08-18 11:02 ` H. Nikolaus Schaller
2016-08-18 11:41 ` Marcel Holtmann
2016-08-18 12:07 ` H. Nikolaus Schaller
2016-08-18 11:02 ` Pavel Machek
2016-08-18 13:07 ` Linus Walleij
2016-08-18 17:31 ` Marcel Holtmann
2016-08-18 14:25 ` One Thousand Gnomes
2016-08-18 15:14 ` H. Nikolaus Schaller
[not found] ` <20160818163809.1b2fcfe5@lxorguk.ukuu.org.uk>
2016-08-18 18:31 ` H. Nikolaus Schaller
2016-08-18 22:25 ` Rob Herring
2016-08-19 11:38 ` One Thousand Gnomes
2016-08-19 15:36 ` Sebastian Reichel
2016-08-18 20:29 ` Sebastian Reichel
2016-08-18 23:08 ` Rob Herring
2016-08-19 5:21 ` Sebastian Reichel
2016-08-19 7:29 ` H. Nikolaus Schaller
2016-08-19 7:49 ` Oleksij Rempel
2016-08-19 17:50 ` H. Nikolaus Schaller
2016-08-19 20:19 ` Oleksij Rempel
2016-08-20 13:34 ` One Thousand Gnomes
2016-08-21 7:50 ` H. Nikolaus Schaller
2016-08-22 20:39 ` Sebastian Reichel
2016-08-22 21:23 ` H. Nikolaus Schaller
2016-08-22 21:43 ` Arnd Bergmann
2016-08-22 22:42 ` Sebastian Reichel
2016-08-22 22:52 ` One Thousand Gnomes
2016-08-22 23:10 ` Sebastian Reichel
2016-08-23 7:28 ` H. Nikolaus Schaller
2016-08-27 12:01 ` Michal Suchanek
2016-08-19 11:06 ` One Thousand Gnomes
2016-08-19 17:42 ` H. Nikolaus Schaller
2016-08-20 13:22 ` One Thousand Gnomes
2016-08-21 7:50 ` H. Nikolaus Schaller
2016-08-21 17:09 ` One Thousand Gnomes
2016-08-21 18:23 ` H. Nikolaus Schaller
2016-08-22 9:09 ` One Thousand Gnomes
2016-08-22 9:33 ` Marcel Holtmann
2016-08-19 11:03 ` One Thousand Gnomes
2016-08-19 14:44 ` Sebastian Reichel
2016-08-22 12:37 ` Arnd Bergmann
2016-08-22 13:38 ` Rob Herring
2016-08-22 15:24 ` Arnd Bergmann
2016-08-22 15:28 ` Marcel Holtmann
2016-08-22 15:46 ` Arnd Bergmann
2016-08-22 15:45 ` One Thousand Gnomes
2016-08-22 21:07 ` Marcel Holtmann
2016-08-22 21:35 ` One Thousand Gnomes
2016-08-22 22:03 ` Sebastian Reichel
2016-08-22 22:46 ` One Thousand Gnomes
2016-08-22 23:41 ` Sebastian Reichel
2016-08-24 12:14 ` Linus Walleij
2016-08-22 16:44 ` Rob Herring
2016-08-22 17:02 ` One Thousand Gnomes
2016-08-22 17:30 ` Rob Herring
2016-08-22 17:38 ` One Thousand Gnomes
2016-08-22 21:16 ` Marcel Holtmann
2016-08-22 21:32 ` One Thousand Gnomes
2016-08-22 22:00 ` Pavel Machek
2016-08-22 22:54 ` One Thousand Gnomes
2016-08-22 23:57 ` Sebastian Reichel
2016-08-23 0:15 ` One Thousand Gnomes
2016-08-23 0:57 ` Sebastian Reichel
2016-08-24 13:57 ` One Thousand Gnomes
2016-08-24 14:29 ` Marcel Holtmann
2016-08-23 11:42 ` Marcel Holtmann
2016-08-22 23:02 ` Sebastian Reichel
2016-08-22 20:00 ` Sebastian Reichel
2016-08-22 22:00 ` Rob Herring
2016-08-22 22:18 ` Sebastian Reichel
2016-08-23 21:04 ` Rob Herring
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