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

From	One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH 0/3] UART slave device bus
Date	2016-08-21 19:20 +0200
Message-ID	<s8EzD-3dF-7@gated-at.bofh.it> (permalink)
References	(4 earlier) <s7Mzh-2Fi-85@gated-at.bofh.it> <s7PQu-4Rb-9@gated-at.bofh.it> <s7W5A-aY-11@gated-at.bofh.it> <s8evv-3Bs-3@gated-at.bofh.it> <s8vPI-5WQ-15@gated-at.bofh.it>
Organization	Intel Corporation

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> Let me ask a question about your centralized and pre-cooked buffering approach.
> 
> As far as I see, even then the kernel API must notify the driver at the right moment
> that a new block has arrived. Right?

The low level driver queues words (data byte, flag byte)
The buffer processing workqueue picks those bytes from the queue and
atomically empties the queue
The workqueue involves the receive handler.

> But how does the kernel API know how long such a block is?

It's as long as the data that has arrived in that time.

> Usually there is a start byte/character, sometimes a length indicator, then payload data,
> some checksum and finally a stop byte/character. For NMEA it is $, no length, * and \r\n.
> For other serial protocols it might be AT, no length, and \r. Or something different.
> HCI seems to use 2 byte op-code or 1 byte event code and 1 byte parameter length.

It doesn't look for any kind of protocol block headers. The routine
invoked by the work queue does any frame recovery.

> So I would even conclude that you usually can't even use DMA based UART receive
> processing for arbitrary and not well-defined protocols. Or have to assume that the

We do, today for bluetooth and other protocols just fine - it's all about
data flows not about framing in the protocol sense.

Alan

Thread

[RFC PATCH 0/3] UART slave device bus Rob Herring <robh@kernel.org> - 2016-08-18 03:20 +0200
  Re: [RFC PATCH 0/3] UART slave device bus Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-18 12:30 +0200
    Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-18 12:40 +0200
      Re: [RFC PATCH 0/3] UART slave device bus Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-18 13:00 +0200
        Re: [RFC PATCH 0/3] UART slave device bus Rob Herring <robh@kernel.org> - 2016-08-18 16:00 +0200
    Re: [RFC PATCH 0/3] UART slave device bus Rob Herring <robh@kernel.org> - 2016-08-18 15:20 +0200
      Re: [RFC PATCH 0/3] UART slave device bus Rob Herring <robh@kernel.org> - 2016-08-19 03:50 +0200
        Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-19 13:10 +0200
  Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-18 12:40 +0200
    Re: [RFC PATCH 0/3] UART slave device bus Pavel Machek <pavel@ucw.cz> - 2016-08-18 12:50 +0200
      Re: [RFC PATCH 0/3] UART slave device bus Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-18 13:00 +0200
        Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-18 13:20 +0200
        Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-18 16:50 +0200
      Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-18 13:00 +0200
      Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-18 13:30 +0200
    Re: [RFC PATCH 0/3] UART slave device bus Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-18 13:00 +0200
      Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-18 13:10 +0200
        Re: [RFC PATCH 0/3] UART slave device bus Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2016-08-18 13:30 +0200
          Re: [RFC PATCH 0/3] UART slave device bus Pavel Machek <pavel@ucw.cz> - 2016-08-18 13:50 +0200
          Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-18 14:00 +0200
      Re: [RFC PATCH 0/3] UART slave device bus Pavel Machek <pavel@ucw.cz> - 2016-08-18 13:20 +0200
        Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-18 13:20 +0200
          Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-18 13:50 +0200
            Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-18 14:20 +0200
        Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-18 13:50 +0200
          Re: [RFC PATCH 0/3] UART slave device bus Pavel Machek <pavel@ucw.cz> - 2016-08-18 15:10 +0200
    Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-18 13:00 +0200
      Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-18 13:10 +0200
        Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-18 13:50 +0200
          Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-18 14:10 +0200
  Re: [RFC PATCH 0/3] UART slave device bus Pavel Machek <pavel@ucw.cz> - 2016-08-18 13:10 +0200
  Re: [RFC PATCH 0/3] UART slave device bus Linus Walleij <linus.walleij@linaro.org> - 2016-08-18 15:20 +0200
    Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-19 03:50 +0200
  Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-18 16:30 +0200
    Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-19 03:10 +0200
    Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-19 03:30 +0200
    Re: [RFC PATCH 0/3] UART slave device bus Rob Herring <robh@kernel.org> - 2016-08-19 04:50 +0200
      Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-19 13:40 +0200
        Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-19 17:40 +0200
  Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-19 03:30 +0200
    Re: [RFC PATCH 0/3] UART slave device bus Rob Herring <robh@kernel.org> - 2016-08-19 03:40 +0200
      Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-19 07:30 +0200
        Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-19 09:40 +0200
          Re: [RFC PATCH 0/3] UART slave device bus Oleksij Rempel <linux@rempel-privat.de> - 2016-08-19 10:00 +0200
            Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-19 20:00 +0200
              Re: [RFC PATCH 0/3] UART slave device bus Oleksij Rempel <linux@rempel-privat.de> - 2016-08-19 22:30 +0200
              Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-20 15:40 +0200
                Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-21 10:00 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-22 22:50 +0200
                Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-22 23:30 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Arnd Bergmann <arnd@arndb.de> - 2016-08-22 23:50 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-23 00:50 +0200
                Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-23 01:00 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-23 01:20 +0200
                Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-23 09:30 +0200
          Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-19 13:10 +0200
            Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-19 19:50 +0200
              Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-20 15:30 +0200
                Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-21 10:00 +0200
                Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-21 19:20 +0200
                Re: [RFC PATCH 0/3] UART slave device bus "H. Nikolaus Schaller" <hns@goldelico.com> - 2016-08-21 20:30 +0200
                Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-22 11:20 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-22 11:40 +0200
        Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-19 13:10 +0200
          Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-19 16:50 +0200
  Re: [RFC PATCH 0/3] UART slave device bus Arnd Bergmann <arnd@arndb.de> - 2016-08-22 14:40 +0200
    Re: [RFC PATCH 0/3] UART slave device bus Rob Herring <robh@kernel.org> - 2016-08-22 15:50 +0200
      Re: [RFC PATCH 0/3] UART slave device bus Arnd Bergmann <arnd@arndb.de> - 2016-08-22 17:30 +0200
        Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-22 17:30 +0200
          Re: [RFC PATCH 0/3] UART slave device bus Arnd Bergmann <arnd@arndb.de> - 2016-08-22 18:00 +0200
        Re: [RFC PATCH 0/3] UART slave device bus Rob Herring <robh@kernel.org> - 2016-08-22 18:50 +0200
          Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-22 19:10 +0200
            Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-22 19:40 +0200
              Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-22 23:20 +0200
                Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-22 23:40 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Pavel Machek <pavel@ucw.cz> - 2016-08-23 00:10 +0200
                Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-23 01:00 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-23 02:00 +0200
                Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-23 02:20 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-23 03:00 +0200
                Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-24 16:00 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-24 16:40 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-23 13:50 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-23 01:10 +0200
            Re: [RFC PATCH 0/3] UART slave device bus Rob Herring <robh@kernel.org> - 2016-08-22 19:40 +0200
              Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-22 22:10 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Rob Herring <robh@kernel.org> - 2016-08-23 00:10 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-23 00:20 +0200
        Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-22 19:20 +0200
          Re: [RFC PATCH 0/3] UART slave device bus Marcel Holtmann <marcel@holtmann.org> - 2016-08-22 23:10 +0200
            Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-23 00:10 +0200
              Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-23 01:20 +0200
                Re: [RFC PATCH 0/3] UART slave device bus Sebastian Reichel <sre@kernel.org> - 2016-08-23 01:50 +0200
            Re: [RFC PATCH 0/3] UART slave device bus One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-08-23 00:20 +0200
          Re: [RFC PATCH 0/3] UART slave device bus Linus Walleij <linus.walleij@linaro.org> - 2016-08-24 14:30 +0200
        Re: [RFC PATCH 0/3] UART slave device bus Rob Herring <robh@kernel.org> - 2016-08-23 23:20 +0200

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