linux-kernel - RE: Hyper-V TODO file

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Message-ID: <6E21E5352C11B742B20C142EB499E048081C7981@TK5EX14MBXC126.redmond.corp.microsoft.com>
Date:	Fri, 2 Sep 2011 20:54:37 +0000
From:	KY Srinivasan <kys@...rosoft.com>
To:	Greg KH <greg@...ah.com>
CC:	"gregkh@...e.de" <gregkh@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"virtualization@...ts.osdl.org" <virtualization@...ts.osdl.org>
Subject: RE: Hyper-V TODO file



> -----Original Message-----
> From: Greg KH [mailto:greg@...ah.com]
> Sent: Friday, September 02, 2011 3:58 PM
> To: KY Srinivasan
> Cc: gregkh@...e.de; linux-kernel@...r.kernel.org;
> devel@...uxdriverproject.org; virtualization@...ts.osdl.org
> Subject: Re: Hyper-V TODO file
> 
> On Fri, Sep 02, 2011 at 07:47:12PM +0000, KY Srinivasan wrote:
> >
> >
> > > -----Original Message-----
> > > From: Greg KH [mailto:greg@...ah.com]
> > > Sent: Thursday, September 01, 2011 4:31 PM
> > > To: KY Srinivasan
> > > Cc: gregkh@...e.de; linux-kernel@...r.kernel.org;
> > > devel@...uxdriverproject.org; virtualization@...ts.osdl.org
> > > Subject: Re: Hyper-V TODO file
> > >
> > > On Thu, Sep 01, 2011 at 01:27:33PM -0700, Greg KH wrote:
> > > > On Wed, Aug 31, 2011 at 03:16:51PM -0700, K. Y. Srinivasan wrote:
> > > > > 2) With your help, we have fixed all of the issues related to these drivers
> > > > > conforming to the Linux Device Driver model. One of the TODO work
> items is
> > > > > "audit the vmbus to verify it is working properly with the driver model".
> > > >
> > > > I have a few comments about this, I'll respond in another email.
> > >
> > > Ok, it looks a _lot_ better, but I have a few minor nits, and one larger
> > > one:
> > >
> > > - rename the vmbus_child_* functions to vmbus_* as there's no need to
> > >   think of "children" here.
> > >
> > > - vmbus_onoffer comment is incorrect.  You handle offers from lots of
> > >   other types.  Or if not, am I reading the code incorrectly?
> > >
> > > - the static hv_cb_utils array needs to go away.  In the hv_utils.c
> > >   util_probe() call, properly register the channel callback, and the
> > >   same goes for the util_remove() call, unregister things there.
> > >   Note, you can use the driver_data field to determine exactly which
> > >   callback needs to be registered to make things easy.  Something like
> > >   the following (pseudo code only):
> > >
> > > static const struct hv_vmbus_device_id id_table[] = {
> > > 	/* Shutdown guid */
> > > 	{ VMBUS_DEVICE(0x31, 0x60, 0x0B, 0X0E, 0x13, 0x52, 0x34, 0x49,
> > > 		       0x81, 0x8B, 0x38, 0XD9, 0x0C, 0xED, 0x39, 0xDB),
> > > 	  .driver_data = &shutdown_onchannelcallback },
> > > 	....
> > > };
> > >
> > > util_probe(struct hv_device *dev, const struct hv_vmbus_device_id *id)
> > >  [ Yes, you will have to change the probe callback signature, but that's fine. ]
> >
> > Greg, I think if I understand you correctly, the id parameter to the probe
> function
> > would be pointing to relevant entry in the hv_vmbus_device_id array.
> 
> Yes, just like it does for USB, PCI, etc.
> 
> > Since the driver can handle multiple ids (guids), we need to either in
> > the driver specific probe function or in the bus specific probe
> > function,  figure out which of the many devices the driver supports is
> > being probed. I have couple of implementation options and would
> > appreciate your preference:
> >
> > 1) Do the guid parsing at the vmbus level parsing function. If I go
> > this route, the driver specific probe function would get an extra
> > parameter as you have described in pseudo code.
> 
> Yes, that's the proper way to do this, as your match function already
> found the proper id structure, so you have the pointer, just pass it to
> the probe function callback.
> 
> > 2) Do the guid parsing in the util probe function. In this case, we
> > don't need to change the signature for the probe function as all the
> > id information is available in the (util) driver.
> 
> Yes, but you end up doing the matching all over again in the util
> driver, which isn't nice and ripe for duplication and bugs.
> 
> > I personally would prefer the second approach since it does not affect
> > other drivers (no need to change the signature for the probe
> > function). Let me know how you want me to proceed here.
> 
> As you only have 3 probe functions, it's not a big deal to change them
> all :)

Ok; will do. I am glad I checked with you!

Regards,

K. Y

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