linux-kernel - Re: [PATCH 3/3] staging: vme: make match() driver specific to improve non-VME64x support

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Message-ID: <20110926141603.GB16310@becoht-mvanga>
Date:	Mon, 26 Sep 2011 16:16:03 +0200
From:	Manohar Vanga <manohar.vanga@...n.ch>
To:	"Emilio G. Cota" <cota@...ap.org>
CC:	<gregkh@...e.de>, <martyn.welch@...com>,
	<devel@...verdev.osuosl.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] staging: vme: make match() driver specific to
 improve non-VME64x support

Hey Emilio,

> > +	/* Initialize the list for bridge devices */
> > +	INIT_LIST_HEAD(&tsi148_bridge->devices);
> > +
> 
> Probably it makes more sense to handle this in vme.c:vme_add_bus(), since
> the particular bridge drivers do not manage at all the device list.

I thought of doing this but decided to go the other way for some forgotten
reason. I think it was the fact that there would be a gap between allocation
and initialization that bothered me.

Anyway, I've changed it and it is now done in vme_add_bus().

> > -#define USER_BUS_MAX                  1
> > +#define VME_USER_BUS_MAX	1
> 
> this could be another patch, but duh..

Done.

> >  int vme_register_bridge(struct vme_bridge *bridge)
> >  {
> > -	struct vme_dev *vdev;
> > -	int retval;
> > -	int i;
> > +	return vme_add_bus(bridge);
> > +}
> > +EXPORT_SYMBOL(vme_register_bridge);
> 
> Consider sending a subsequent patch cleaning up functions like these.
> But don't do it in this patch; this patch, if anything, needs to go
> on a diet.
> 
> > -	retval = vme_add_bus(bridge);
> > -	if (retval)
> > -		return retval;
> > +void vme_unregister_bridge(struct vme_bridge *bridge)
> > +{
> > +	vme_remove_bus(bridge);
> > +}
> > +EXPORT_SYMBOL(vme_unregister_bridge);
> 
> ditto

I'm not sure I understood this entirely. This replaces the old function
with the new one. There isn't any cleanup here. Or did I understand something
wrongly?

> > +/* - Driver Registration --------------------------------------------------- */
> 
> I know you're keeping this comment from what's already in the file,
> but personally I simply find it distracting.

Well there are others as well, so I've left it there for now.

> > +		} else
> > +			device_unregister(&vdev->dev);
> > +	}
> > +	return 0;
> >  
> > -err_reg:
> > +err_dev_reg:
> 
> Leaving the previous label would be better, it's easier to review.
> 
> >  	kfree(vdev);
> > -err_devalloc:
> > -	while (--i >= 0) {
> > -		vdev = bridge->dev[i];
> > +err_alloc:
> 
> ditto

Done.

> > -int vme_register_driver(struct vme_driver *drv)
> > +int vme_register_driver(struct vme_driver *drv, unsigned int ndevs)
> >  {
> > +	int err;
> > +
> >  	drv->driver.name = drv->name;
> >  	drv->driver.bus = &vme_bus_type;
> > +	INIT_LIST_HEAD(&drv->devices);
> > +
> > +	err = driver_register(&drv->driver);
> > +	if (err)
> > +		return err;
> >  
> > -	return driver_register(&drv->driver);
> > +	err = __vme_register_driver(drv, ndevs);
> > +	if (err)
> > +		vme_unregister_driver(drv);
> 
> If __vme_register_driver() fails, we can be sure the created devices
> (and their corresponding lists) have been cleaned up before the
> function returned the failure. So here it seems clearer to call
> unregister_driver().

Agreed. Fixed in the resend.

> >  void vme_unregister_driver(struct vme_driver *drv)
> >  {
> > +	struct vme_dev *dev, *dev_tmp;
> > +
> > +	list_for_each_entry_safe(dev, dev_tmp, &drv->devices, drv_list) {
> > +		list_del(&dev->drv_list);
> > +		list_del(&dev->bridge_list);
> > +		device_unregister(&dev->dev);
> > +	}
> 
> All code operating on both lists is protected by vme_buses_lock, except the
> one in this function, which seems dangerous. vme_unregister_driver may race
> with vme_unregister_bridge. We need to acquire the lock here too.

Fixed.

> >  struct vme_device_id {
> > +	int num;
> >  	int bus;
> >  	int slot;
> 
> As I mentioned earlier, AFAICT the slot field is meaningless now.
> Consider submitting a subsequent patch that removes it.

Done. See resend.

> >  int vme_slot_get(struct vme_dev *);
> 
> AFAICT this is an exported symbol that after this patch has no callers
> and no meaning. Consider submitting a subsequent patch that removes it,
> possibly together with the removal of struct vme_device_id.slot.
> btw remember to update the documentation, I'm sure I'd forget.

This returns the geographical location of the bridge device. Would this
be useful for VME64x crates? I see it isn't used anywhere so I can't imagine
when it might be needed. Maybe Martyn can clarify?

-- 
/manohar
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