Subject: Re: [PATCH/RFC 1/4]device core changes
From: Li Shaohua <shaohua.li@intel.com>
To: Greg KH <greg@kroah.com>
Cc: ACPI-DEV <acpi-devel@lists.sourceforge.net>,
       lkml <linux-kernel@vger.kernel.org>, Len Brown <len.brown@intel.com>,
       Patrick Mochel <mochel@digitalimplant.org>
In-Reply-To: <20041108225810.GB16197@kroah.com>
References: <1099887071.1750.243.camel@sli10-desk.sh.intel.com>
	 <20041108225810.GB16197@kroah.com>
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Date: Tue, 09 Nov 2004 08:50:18 +0800
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On Tue, 2004-11-09 at 06:58, Greg KH wrote:
> On Mon, Nov 08, 2004 at 12:11:11PM +0800, Li Shaohua wrote:
> > Hi,
> > This is the device core change required. Add .platform_bind method for
> > bus_type, so platform can do addition things when add a new device. A
> > case is ACPI, we want to utilize some ACPI methods for physical devices.
> > 1. Why doesn't use 'platform_notify'?
> > Current device core has a 'platform_notify' mechanism, but it's not
> > sufficient for this. Only sepcific bus type know how to parse dev.bus_id
> > and know how to encode specific device's address into ACPI _ADR syntax.
> 
> I don't see why platform_notify is not sufficient.  This is the exact
> reason it was added to the code.
As I said in the email, we need know the bus type to decode and encode
address. If you use platform_notify, you must do something like this:
switch (dev->bus)
{
case pci_bus_type:
bind PCI devices with ACPI devices
break;
case ide_bus_type:
bind IDE devices with ACPI devices
break;
....
}
But note this method requires all bus types are build-in. If a bus type
is in a loadable module (such as IDE bus), the method will failed. I
searched current tree, only ARM implemented 'platform_notify', but ARM
only cares PCI bus, ACPI cares about all bus types.
> 
> > 2. Why adds new 'handle' in 'struct device'?
> > 'Platform_data' is the best candidate, but a search shows some drivers
> > have used it. We can remove 'handle' after the drivers changes their
> > behavior.
> 
> No, fix the drivers.  Don't add something that you are going to remove
> later.
Ok, I'll try to fix them.

Thanks,
Shaohua

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