Re: [PATCH 1/1] usb: chipidea: host: add own hc_driver for each hcd

[Peter Chen <peter.chen@freescale.com>]

On Fri, Jul 17, 2015 at 09:52:26AM -0400, Alan Stern wrote:
> On Fri, 17 Jul 2015, Peter Chen wrote:
> 
> > There are several benefits for doing like this:
> > 
> > - hc_driver can be customized for each hcd
> > - Other hcd hc_driver's initialization will not affect current one.
> > We run out NULL pointer dereference problem when one hcd is started
> > by module_init, and the other is started by otg thread at SMP platform.
> > The reason for this problem is ehci_init_driver will do memory copy
> > for current uniform hc_driver, and this memory copy will do memset (as 0)
> > first, so when the first hcd is running usb_add_hcd, and the second
> > hcd may clear the uniform hc_driver's space (at ehci_init_driver),
> > then the first hcd will meet NULL pointer at the same time.
> 
> It seems to me the real problem is that ehci_init_driver gets called at
> the wrong time.  It's not supposed to be called whenever a new host
> controller is initialized; rather, it should be called just once when
> the driver is initialized.  This means the call should be in a
> module_init routine in host.c, not in ci_hdrc_host_init.
> 

But we have no platform driver dedicated for host controller, is it a
must? The core driver requests io_address, interrupt, dma_mask, etc for
both device and host driver, and device and host part (we does not take
it as a driver) should not request resources again.

Would you accept it as another use case for ehci driver?

> If you need to customize the hc_driver structure for each host 
> controller then yes, a separate copy is needed.  But otherwise there's 
> no need to make a copy.
> 
> Alan Stern
> 

-- 

Best Regards,
Peter Chen