On Saturday 20 September 2008, Russell King - ARM Linux wrote:
> On Fri, Sep 19, 2008 at 05:41:44PM -0700, David Brownell wrote:
> > On Friday 19 September 2008, Felipe Balbi wrote:
> > > static int omap_wdt_open(struct inode *inode, struct file *file)
> > > {
> > > - struct omap_wdt_dev *wdev;
> > > - void __iomem *base;
> > > - wdev = platform_get_drvdata(omap_wdt_dev);
> > > - base = wdev->base;
> > > + struct omap_wdt_dev *wdev = platform_get_drvdata(omap_wdt_dev);
> > > + void __iomem *base = wdev->base;
> > > +
> >
> > Oh, I see where "omap_wdt_dev" (global) gets used. The normal
> > way to do stuff like that is using void* pointers placed in the
> > inode and file structures for exactly that purpose.
>
> You don't have an inode or a file structure until open() is called -
> at which point it _is_ placed in file->private_data. So this driver
> is doing the right thing.
Well, the conventional thing for misc drivers, at any rate. In
various other drivers, inode->i_private is set up earlier, just
to avoid such a need for globals (or equivalent).
One could argue that this idiom is ugly ... and fix it by having
misc_open() in drivers/char/misc.c initialize i_private before
delegating to the miscdevice->fops->open(). Even just setting
it to the miscdevice pointer would suffice with this driver;
container_of(i_private, struct omap_wdt_dev, omap_wdt_miscdev)
would then return what get_drvdata() returns, sans global.
But that wouldn't be just cleaning up this watchdog.
= Dave
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