On Wed, 12 Aug 2015, Peter Chen wrote:
> On Tue, Aug 11, 2015 at 09:43:13AM +0000, Barry Song wrote:
> > From: Rong Wang <Rong.Wang@xxxxxxx>
> >
> > Chipidea puts ci information to drvdata, but this overwrites the drvdata
> > placed by EHCI core. EHCI core thinks drvdata is ehci_hcd. We can find this
> > from codes like ehci-sysfs.c:
> > static ssize_t show_companion(struct device *dev,
> > struct device_attribute *attr,
> > char *buf)
> > {
> > struct ehci_hcd *ehci;
> >
> > ehci = hcd_to_ehci(bus_to_hcd(dev_get_drvdata(dev)));
> > ...
> > }
> >
> > So overwritting drvdata from chipidea driver actually breaks a part of
> > functionalities of EHCI core.
> >
> > Since the platform_data would not be accessed after the device is added
> > to system after the probe process, so it's safe to move to platform_data
> > here. This fix is not elegant but currently it is the quickest fix.
>
> Yes, it is indeed a fix, but using platform_data as driver private data
> is not so good, let me consider if we have a better solution.
>
> Add Alan
> Alan, do you have any suggestions? Currently, IP core driver and ehci
> core both takes its internal structure as driver data. Thanks.
It's not just ehci-hcd: The USB core stores the hcd address as driver
data. usb_create_shared_hcd() does:
dev_set_drvdata(dev, hcd);
(The core uses this value only in usb_hcd_platform_shutdown(), but
other platform-glue drivers also store the hcd address there.)
The standard answer is to put the Chipidea private data in the
ehci_ci_priv structure. That's what it's meant for.
Is that okay for you? It might be troublesome in cases where the
system acts as a USB peripheral only -- then you might not have an
ehci_hcd structure at all. One solution is always to create the
ehci_hcd; another solution is to store the Chipidea private data as
driver data whenever you don't create the ehci_hcd. But that would
also be difficult, because then you would have to know which case you
were in.
I'm open to other suggestions.
Alan Stern
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