Messages in this thread | | | Date | Wed, 24 Mar 2010 22:35:23 +0530 (IST) | From | Pavan Savoy <> | Subject | Re: [PATCH 4/6] drivers:misc: sources for Init manager module |
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--- On Wed, 24/3/10, Greg KH <gregkh@suse.de> wrote:
> From: Greg KH <gregkh@suse.de> > Subject: Re: [PATCH 4/6] drivers:misc: sources for Init manager module > To: "Pavan Savoy" <pavan_savoy@yahoo.co.in> > Cc: "Marcel Holtmann" <marcel@holtmann.org>, "PavanSavoy" <pavan_savoy@ti.com>, "alan@lxorguk.ukuu.org.uk" <alan@lxorguk.ukuu.org.uk>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org> > Date: Wednesday, 24 March, 2010, 10:22 PM > On Wed, Mar 24, 2010 at 10:05:19PM > +0530, Pavan Savoy wrote: > > --- On Wed, 24/3/10, Greg KH <gregkh@suse.de> > wrote: > > > > > From: Greg KH <gregkh@suse.de> > > > Subject: Re: [PATCH 4/6] drivers:misc: sources > for Init manager module > > > To: "Marcel Holtmann" <marcel@holtmann.org> > > > Cc: "Pavan Savoy" <pavan_savoy@yahoo.co.in>, > "PavanSavoy" <pavan_savoy@ti.com>, > "alan@lxorguk.ukuu.org.uk" > <alan@lxorguk.ukuu.org.uk>, > "linux-kernel@vger.kernel.org" > <linux-kernel@vger.kernel.org> > > > Date: Wednesday, 24 March, 2010, 9:56 PM > > > On Wed, Mar 24, 2010 at 09:11:45AM > > > -0700, Marcel Holtmann wrote: > > > > > I wanted to somehow put this in staging > because > > > then it would probably have a thorough > architectural review > > > process. > > > > > Some details about this driver - > > > > > > > > > > 1. This driver will be used by > > > Bluetooth-BlueZ/FM-V4L2 and GPS (probably > character device > > > driver) using the EXPORTED symbols > (-register/_unregister). > > > > > > > > > > 2. Much like the hciattach daemon which > maintains > > > N_HCI bluetooth line discipline, this driver will > also have > > > a User-Space? N_TI_WL Init manager (UIM) > maintaining > > > the Line discipline. > > > > > > > > can you explain why you think this is needed > and we > > > can not interface > > > > this directly. If it is a serial port, what > protocol > > > does it talk? > > > > > > > > > 3. Because of the UIM should know when > to > > > install/uninstall line discipline, the /sys entry > is created > > > a root called UIM (a new kobject) and UIM daemon > would write > > > it's PID to it. > > > > > > > > I don't understand this. This sounds like a > broken > > > concept to me. > > > > > > I also agree, those sysfs files are not > acceptable, and > > > will not work > > > as-designed due to the pid namespace issues :( > > > > Ok, How do I then from kernel space, ask a user-space > daemon to open the TTY port and do a tiocsetd on it ? > > [i.e ask for a line discipline to be installed ?] > > What would cause the kernel to want to tell userspace to do > this? Is it > an external event that happens somehow that userspace > should know to > look for?
Yes, Userspace events like opening the /dev/radio0 device for FM, or hci0 interface for BT. However the apps/stack would not want to know what LDISC is being used underneath, well they might not even want to know whether it's TTY or USB/i2C - right ?
> > Can't open the TTY and TIOCSETD upon boot, because BT, > FM and GPS > > might be used or not used anytime. > > What causes them to want to be used? The user, > right? > > > And the idea of creating a device node, specifically > for this and then > > doing an fasync/SIGIO was somehow rubbished. > > Why?
It does pretty much the same thing, But we would be stuffing in more interfaces to the already huge driver. I mean just 3 fops on the device ? open/ioctl-fasync/close - but it also uses the SIGnaling concept - but not via PID though.
Alan's talking about opening up the LDISC installation to kernel (say EXPORTING tty_set_ldisc/tiocsetd), That's like ideal scenario in this case.
> > thanks, > > greg k-h >
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