linux-kernel - RE: [PATCH 1/2] drivers:bluetooth: TI

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Message-ID: <1286466576.6145.161.camel@aeonflux>
Date:	Thu, 07 Oct 2010 17:49:36 +0200
From:	Marcel Holtmann <marcel@...tmann.org>
To:	"Savoy, Pavan" <pavan_savoy@...com>
Cc:	"linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
	"johan.hedberg@...il.com" <johan.hedberg@...il.com>,
	"greg@...ah.com" <greg@...ah.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] drivers:bluetooth: TI_ST bluetooth driver

Hi Pavan,

> > > > > > Registering the Bluetooth HCI driver in module_init/module_exit is not
> > > > > > acceptable. Turn your shared transport into a proper bus.
> > > > >
> > > > > Yes, you did comment on it before, I remember, I did prototype the
> > driver as
> > > > > a bus driver, However I didn't find any advantages by converting it to a
> > bus
> > > > > driver.
> > > > > As in, currently the shared transport driver is a line discipline driver
> > > > because
> > > > > it is the only way it can communicate over TTY without being tightly
> > coupled
> > > > with the UART driver.
> > > > >
> > > > > > We want to be able to have generic kernels where this module is
> > enabled,
> > > > > > but no Shared Transport is available.
> > > > >
> > > > > Oh if this is the reason I cannot have hci_register/_unregister in
> > > > module_init/_exit, Can I do this module "depends" on TI_ST, Then it would
> > not
> > > > > even be visible to build if TI_ST is not selected.
> > > >
> > > > this is not helping either. Then TI_ST can not be selected and so you
> > > > still end up with some weird platform specific kernels. We don't want
> > > > that. We want generic kernels that can detect the hardware they are
> > > > running on.
> > > >
> > > > As I said, I will not accept this driver if it registers HCI device in
> > > > module_init. No other driver is doing this and it is in general a really
> > > > really really bad idea.
> > > >
> > >
> > > Ok, now I am beginning to get what you say, Let me check, may be what
> > > I can do is, have something like a st_prepare() function called in the
> > > module_init, and a _probe function of the bluetooth driver will be called,
> > > _ONLY_ if the _probe of my platform driver has been called..
> > > Do you think this would be a good idea?
> > >
> > > Note: the TI_ST driver is also a platform device driver, so that TI_ST's
> > > Probe is not called, if a arch/xx/board-xx doesn't add it.
> > 
> > that that should be your bus right there.
> 
> I understand the perspective, but "bus" is not device-driver type of model right? I mean I need a device which will be added in some platform specific
> board file, and the driver in my driver core file.
> 
> > Let me repeat this. If you register the HCI device in module_init then
> > it will be registered on all platform this module is selected. Even if
> > the kernel runs on x86. And that is not acceptable. Registering devices
> > in module_init is a bad idea no matter what. That is why all other
> > drivers just register a driver here and not a device.
> 
> I did initially think about making each of the protocol drivers a 
> platform devices as well.
> As in Bluetooth/FM/GPS TI_ST driver would also be a platform device and its _probe doing the HCI/v4L2/character device registration.
> 
> So which one do you think makes more sense here?
> 1. Do I EXPORT a new symbol called st_prepare? And allow hci registration there?
> 
> 2. Or make Bluetooth device a platform device and this driver a platform driver
> and add this Bluetooth device only when I add TI_ST platform device?

then make them a platform device. Since you do need a proper parent for
these devices anyway. Otherwise a lot of logic within sysfs will fail.

Regards

Marcel


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