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Re: [patch 0/7] staging: speakup: introduce tty-based comms

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Samuel Thibault, on mar. 14 mars 2017 01:47:01 +0100, wrote:
> Greg KH, on mar. 14 mars 2017 06:14:04 +0800, wrote:
> > On Mon, Mar 13, 2017 at 10:05:51PM +0000, okash.khawaja@gmail.com wrote:
> > > This patchset introduces a TTY-based way for the synths to communicate
> > > with devices as an alternate for direct serial comms used by the synths
> > > at the moment. It then migrates some of the synths to the TTY-based
> > > comms. Synths migrated in this patchset are dummy, acntsa, bns and
> > > txprt.
> > 
> > What about using the serbus code that is now in the tree?  That should
> > make this a lot easier than your patchset from what I can see.
> 
> Mmm... AIUI from reading tty_port_register_device_attr, one
> would have to have registered a speakup serdev device driver
> *before* tty_port_register_device_attr gets called, so that
> serdev_tty_port_register matches the driver in the loop of
> of_serdev_register_devices, and no TTY cdev is created?
> 
> That would mean that speakup can not be loaded as a module after ttyS0
> initialization, that won't fly for our use needs. The line discipline
> mechanism allows us to attach ourself to an existing tty.  Could we
> imagine a tty_port function which removes the cdev and tries to register
> the tty port again to serdev?
> 
> What we basically need to be able to say on speakup module load is
> e.g. "I'm now attaching a device to ttyS0, use this serdev_device_ops to
> discuss with it".

That for_each_available_child_of_node loop is really way more complex
than what we need.  And what's more, it's not working without CONFIG_OF
(!)

It would really make sense to me to have a

serdev_device *tty_port_register_serdev_device(tty, device)

which unregisters the character device of the tty, and creates instead a
controler with the given device plugged to it. Really much like a line
discipline, but way simpler :)

The issue that remains is the "tty" part: we'd need there the tty_port,
the parent device, the tty driver, the idx. All we know when we load
speakup is "ttyS0". That's where going through the cdev to attach a line
discipline was simpler :)

Samuel

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[patch 0/7] staging: speakup: introduce tty-based comms okash.khawaja@gmail.com - 2017-03-13 23:10 +0100
  Re: [patch 0/7] staging: speakup: introduce tty-based comms Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-13 23:20 +0100
    Re: [patch 0/7] staging: speakup: introduce tty-based comms Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-03-13 23:30 +0100
      Re: [patch 0/7] staging: speakup: introduce tty-based comms Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-03-14 00:50 +0100
      Re: [patch 0/7] staging: speakup: introduce tty-based comms Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-14 00:50 +0100
      Re: [patch 0/7] staging: speakup: introduce tty-based comms Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-03-14 01:10 +0100
    Re: [patch 0/7] staging: speakup: introduce tty-based comms Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-03-14 01:50 +0100
      Re: [patch 0/7] staging: speakup: introduce tty-based comms Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-03-14 02:20 +0100
        Re: [patch 0/7] staging: speakup: introduce tty-based comms Rob Herring <robh@kernel.org> - 2017-03-15 15:50 +0100
          Re: [patch 0/7] staging: speakup: introduce tty-based comms Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-03-15 16:10 +0100
            Re: [patch 0/7] staging: speakup: introduce tty-based comms Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-03-22 01:10 +0100
      Re: [patch 0/7] staging: speakup: introduce tty-based comms Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-03-16 10:30 +0100
  Re: [patch 1/7] tty_port: allow a port to be opened with a tty that  has no file handle Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-03-13 23:20 +0100
    Re: [patch 1/7] tty_port: allow a port to be opened with a tty that  has no file handle Okash Khawaja <okash.khawaja@gmail.com> - 2017-03-13 23:40 +0100
  [patch 6/7] staging: speakup: add tty-based comms functions okash.khawaja@gmail.com - 2017-03-13 23:20 +0100
  [patch 3/7] staging: serial: add spk_io_ops struct to spk_synth okash.khawaja@gmail.com - 2017-03-13 23:20 +0100
  [patch 4/7] staging: speakup: move spk_stop_serial_interrupt into synth-specific release function okash.khawaja@gmail.com - 2017-03-13 23:20 +0100
  [patch 7/7] staging: speakup: migrate acntsa, bns, dummy and txprt to ttyio okash.khawaja@gmail.com - 2017-03-13 23:20 +0100
  [patch 2/7] staging: speakup: spk_serial_out and spk_wait_for_xmitr to take synth arg okash.khawaja@gmail.com - 2017-03-13 23:20 +0100
  [patch 1/7] tty_port: allow a port to be opened with a tty that has no file handle okash.khawaja@gmail.com - 2017-03-13 23:20 +0100
    Re: [patch 1/7] tty_port: allow a port to be opened with a tty that  has no file handle Dan Carpenter <dan.carpenter@oracle.com> - 2017-03-14 10:20 +0100
  [patch 5/7] staging: speakup: move those functions which do outgoing serial comms, into serialio.c okash.khawaja@gmail.com - 2017-03-13 23:20 +0100
  Re: [patch 0/7] staging: speakup: introduce tty-based comms Samuel Thibault <samuel.thibault@ens-lyon.org> - 2017-03-14 01:30 +0100

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