ARM unaligned MMIO access with attribute((packed))
stern at rowland.harvard.edu
Wed Apr 27 12:25:40 EDT 2011
On Wed, 27 Apr 2011, Rabin Vincent wrote:
> On Wed, Apr 27, 2011 at 00:21, Alan Stern <stern at rowland.harvard.edu> wrote:
> > On Tue, 26 Apr 2011, Rabin Vincent wrote:
> >> In my case it's this writel() in ehci-hub.c that gets chopped into
> >> strbs:
> >> /* force reset to complete */
> >> ehci_writel(ehci, temp & ~(PORT_RWC_BITS | PORT_RESET),
> >> status_reg);
> > Why would that get messed up? The status_reg variable doesn't have any
> > __atribute__((packed)) associated with it.
> The initialization of status_reg is:
> u32 __iomem *status_reg
> = &ehci->regs->port_status[(wIndex & 0xff) - 1];
> where ehci->regs is a pointer to the packed struct ehci_regs. So, this
> is the same problem of casting pointers to stricter alignment.
Right. I can understand the compiler complaining about the cast to
stricter alignment during the initialization. But I don't understand
why that would affect the code generated for the writel function.
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