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

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Message-ID: <19F8576C6E063C45BE387C64729E739404AA21D1BD@dbde02.ent.ti.com>
Date:	Thu, 7 Oct 2010 21:17:42 +0530
From:	"Savoy, Pavan" <pavan_savoy@...com>
To:	Marcel Holtmann <marcel@...tmann.org>
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



> -----Original Message-----
> From: Marcel Holtmann [mailto:marcel@...tmann.org]
> Sent: Thursday, October 07, 2010 10:37 AM
> To: Savoy, Pavan
> Cc: linux-bluetooth@...r.kernel.org; johan.hedberg@...il.com; greg@...ah.com;
> 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?

> Regards
> 
> Marcel
> 

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