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

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Date:	Thu, 07 Oct 2010 17:37:23 +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.

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.

Regards

Marcel


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