[U-Boot] [PATCH 1/3] usb: ehci-pci: Clarify and cleanup the EHCI controller detection

[Simon Glass]

On 13 December 2013 21:55, Marek Vasut <marex at denx.de> wrote:
> The detection function of the EHCI PCI controller was really cryptic,
> add a beefy comment and clean the portion of the code up a bit. No
> change in the logic of the code.
>
> Signed-off-by: Marek Vasut <marex at denx.de>
> Cc: Simon Glass <sjg at chromium.org>

Acked-by: Simon Glass <sjg at chromium.org>

> ---
>  drivers/usb/host/ehci-pci.c | 28 +++++++++++++++++++++++++---
>  1 file changed, 25 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/usb/host/ehci-pci.c b/drivers/usb/host/ehci-pci.c
> index 7a1ffe5..991b199 100644
> --- a/drivers/usb/host/ehci-pci.c
> +++ b/drivers/usb/host/ehci-pci.c
> @@ -54,9 +54,31 @@ static pci_dev_t ehci_find_class(int index)
>                                         bdf += PCI_BDF(0, 0, 1)) {
>                                 pci_read_config_dword(bdf, PCI_CLASS_REVISION,
>                                                       &class);
> -                               if ((class >> 8 == PCI_CLASS_SERIAL_USB_EHCI)
> -                                               && !index--)
> -                                       return bdf;
> +                               class >>= 8;
> +                               /*
> +                                * Here be dragons! In case we have multiple
> +                                * PCI EHCI controllers, this function will
> +                                * be called multiple times as well. This
> +                                * function will scan the PCI busses, always
> +                                * starting from bus 0, device 0, function 0,
> +                                * until it finds an USB controller. The USB
> +                                * stack gives us an 'index' of a controller
> +                                * that is currently being registered, which
> +                                * is a number, starting from 0 and growing
> +                                * in ascending order as controllers are added.
> +                                * To avoid probing the same controller in tne
> +                                * subsequent runs of this function, we will
> +                                * skip 'index - 1' detected controllers and
> +                                * report the index'th controller.
> +                                */
> +                               if (class != PCI_CLASS_SERIAL_USB_EHCI)
> +                                       continue;
> +                               if (index) {
> +                                       index--;
> +                                       continue;
> +                               }
> +                               /* Return index'th controller. */
> +                               return bdf;
>                         }
>                 }
>         }
> --
> 1.8.4.3
>