linux-kernel - RE: [PATCH 1/2] drivers:staging:ti-st: move TI

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Date:	Fri, 8 Oct 2010 00:49:07 +0530
From:	"Savoy, Pavan" <pavan_savoy@...com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Jiri Slaby <jirislaby@...il.com>,
	"gregkh@...e.de" <gregkh@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>
Subject: RE: [PATCH 1/2] drivers:staging:ti-st: move TI_ST from staging

Alan,

> -----Original Message-----
> From: Alan Cox [mailto:alan@...rguk.ukuu.org.uk]
> Sent: Thursday, October 07, 2010 2:38 PM
> To: Savoy, Pavan
> Cc: Jiri Slaby; gregkh@...e.de; linux-kernel@...r.kernel.org;
> devel@...verdev.osuosl.org
> Subject: Re: [PATCH 1/2] drivers:staging:ti-st: move TI_ST from staging
> 
> > The situation here was to access the UART from a kernel driver. Say we have
> > a V4L2 FM radio over the UART, How can I write a v4L2 driver? I has to be a
> > line discipline driver correct?
> 
> Why would you want to ? you can just control it from user space. If you
> did want to drive it from the kernel then an ldisc would be one way to do
> it I guess.

ldisc is the ONLY way to do it, isn't it? Do I have any other option?

The situation was something similar here.
What I was trying to get to is how we can have a per-device context if a driver is just a line discipline driver?

Few months ago, something similar was discussed....
I have 3 sub-devices if you will on a device which is interfaced over UART,
One of them is Bluetooth which requires any UART Bluetooth device to have its
Own line discipline - N_HCI.

Another is FM, which needs to be a V4L2 device.
Now being V4L2 device, I need to access the UART from kernel, but I cannot
since BT would be using it via the N_HCI ldisc.

Coming to what Jiri, was commenting was about the ldisc_ops structure, which
Just needs to be static and not really kmalloc-ed in heap.
I did it because, I imagined some day TTY ldisc drivers had capability to have
It's own per-device context/private_data (in addition to) tty driver_data or
Something like tty ldisc_data would be good.

> Alan
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