On Fri, 1 May 2020, Arnd Bergmann wrote:
> On Fri, May 1, 2020 at 4:42 AM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote:
> > On Thu, 30 Apr 2020, Arnd Bergmann wrote:
>
> >
> > No, they don't.
>
> > > /* PORTSC: offset 0x44 */
> > > - u32 port_status[0]; /* up to N_PORTS */
> > > + union {
> > > + u32 port_status[9]; /* up to N_PORTS */
> >
> > This array can have up to 15 elements, meaning that it can extend out
> > to offset 0x80.
>
> Ok, thanks for the clarification!
>
> > > /* EHCI 1.1 addendum */
> > > #define PORTSC_SUSPEND_STS_ACK 0
> > > #define PORTSC_SUSPEND_STS_NYET 1
> > > @@ -165,7 +166,8 @@ struct ehci_regs {
> > > #define PORT_CONNECT (1<<0) /* device connected */
> > > #define PORT_RWC_BITS (PORT_CSC | PORT_PEC | PORT_OCC)
> > >
> > > - u32 reserved3[9];
> > > + u32 reserved3[9];
> > > + };
> > >
> > > /* USBMODE: offset 0x68 */
> > > u32 usbmode; /* USB Device mode */
> >
> > As you see, this next field actually lies inside the preceding array.
> > It's not a real conflict; any hardware which supports the usbmode field
> > uses only the first element of the port_status array.
> >
> > I don't know how you want to handle this. Doing
> >
> > #define usbmode port_status[9]
> >
> > doesn't seem like a very good approach, but I can't think of anything
> > better at the moment. Maybe just set the array size to 9, as you did,
> > but with a comment explaining what's really going on.
>
> The easiest change would be to use an anonymous struct like this
>
> /* PORTSC: offset 0x44 */
> union {
> u32 port_status[15]; /* up to N_PORTS */
> /* EHCI 1.1 addendum */
> #define PORTSC_SUSPEND_STS_ACK 0
> ...
> #define PORT_RWC_BITS (PORT_CSC | PORT_PEC | PORT_OCC)
> struct {
> u32 reserved3[9];
>
> /* USBMODE: offset 0x68 */
> u32 usbmode; /* USB Device mode */
> #define USBMODE_SDIS (1<<3) /* Stream disable */
> #define USBMODE_BE (1<<2) /* BE/LE endianness select */
> #define USBMODE_CM_HC (3<<0) /* host controller mode */
> #define USBMODE_CM_IDLE (0<<0) /* idle state */
>
> u32 reserved4[5];
> };
> };
> u32 reserved5;
>
> It doesn't really improve readability, but it should correctly
> reflect the layout as you described it.
Sounds good. Please go ahead and update the patch.
Alan Stern
