Re: [edk2-devel] [PATCH v2 2/2] MdeModulePkg/Bus/Pci/XhciDxe: Fix MISSING_BREAK Coverity issues

["Laszlo Ersek" <lersek@redhat.com>]

On 11/7/23 06:58, Ranbir Singh wrote:
> From: Ranbir Singh <Ranbir.Singh3@Dell.com>
> 
> The functions
> XhcInitializeEndpointContext and XhcInitializeEndpointContext64 has
> a switch-case code in which the case USB_ENDPOINT_CONTROL: falls
> through to default:
> 
> While this may be intentional, it is not evident to any general code
> reader why there is no break; in between. Adding
> 
>     // No break; here as this is an intentional fallthrough.
> 
> as comment in between makes it explicit. Incidentally, the comment
> satisfies Coverity as well.
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4221
> 
> Cc: Ray Ni <ray.ni@intel.com>
> Co-authored-by: Veeresh Sangolli <veeresh.sangolli@dellteam.com>
> Signed-off-by: Ranbir Singh <Ranbir.Singh3@Dell.com>
> Signed-off-by: Ranbir Singh <rsingh@ventanamicro.com>
> ---
>  MdeModulePkg/Bus/Pci/XhciDxe/XhciSched.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/MdeModulePkg/Bus/Pci/XhciDxe/XhciSched.c b/MdeModulePkg/Bus/Pci/XhciDxe/XhciSched.c
> index 05528a478baf..2afecd40cab0 100644
> --- a/MdeModulePkg/Bus/Pci/XhciDxe/XhciSched.c
> +++ b/MdeModulePkg/Bus/Pci/XhciDxe/XhciSched.c
> @@ -2979,6 +2979,9 @@ XhcInitializeEndpointContext (
>          // Do not support control transfer now.
>          //
>          DEBUG ((DEBUG_INFO, "XhcInitializeEndpointContext: Unsupport Control EP found, Transfer ring is not allocated.\n"));
> +        //
> +        // No break; here as this is an intentional fall through.
> +        //
>        default:
>          DEBUG ((DEBUG_INFO, "XhcInitializeEndpointContext: Unknown EP found, Transfer ring is not allocated.\n"));
>          EpDesc = (USB_ENDPOINT_DESCRIPTOR *)((UINTN)EpDesc + EpDesc->Length);
> @@ -3182,6 +3185,9 @@ XhcInitializeEndpointContext64 (
>          // Do not support control transfer now.
>          //
>          DEBUG ((DEBUG_INFO, "XhcInitializeEndpointContext64: Unsupport Control EP found, Transfer ring is not allocated.\n"));
> +        //
> +        // No break; here as this is an intentional fall through.
> +        //
>        default:
>          DEBUG ((DEBUG_INFO, "XhcInitializeEndpointContext64: Unknown EP found, Transfer ring is not allocated.\n"));
>          EpDesc = (USB_ENDPOINT_DESCRIPTOR *)((UINTN)EpDesc + EpDesc->Length);

Eww, the contradictory DEBUG messages look awkard (in the original code), "unsupported" vs. "unknown"!

How about this one instead:

diff --git a/MdeModulePkg/Bus/Pci/XhciDxe/XhciSched.c b/MdeModulePkg/Bus/Pci/XhciDxe/XhciSched.c
index 05528a478baf..66e2e7044e06 100644
--- a/MdeModulePkg/Bus/Pci/XhciDxe/XhciSched.c
+++ b/MdeModulePkg/Bus/Pci/XhciDxe/XhciSched.c
@@ -3034,6 +3034,7 @@ XhcInitializeEndpointContext64 (
   EFI_PHYSICAL_ADDRESS     PhyAddr;
   UINT8                    Interval;
   TRANSFER_RING            *EndpointTransferRing;
+  UINT8                    EpType;
 
   MaxDci = 0;
 
@@ -3074,7 +3075,8 @@ XhcInitializeEndpointContext64 (
       InputContext->EP[Dci-1].MaxBurstSize = 0x0;
     }
 
-    switch (EpDesc->Attributes & USB_ENDPOINT_TYPE_MASK) {
+    EpType = EpDesc->Attributes & USB_ENDPOINT_TYPE_MASK;
+    switch (EpType) {
       case USB_ENDPOINT_BULK:
         if (Direction == EfiUsbDataIn) {
           InputContext->EP[Dci-1].CErr   = 3;
@@ -3177,13 +3179,16 @@ XhcInitializeEndpointContext64 (
 
         break;
 
-      case USB_ENDPOINT_CONTROL:
-        //
-        // Do not support control transfer now.
-        //
-        DEBUG ((DEBUG_INFO, "XhcInitializeEndpointContext64: Unsupport Control EP found, Transfer ring is not allocated.\n"));
       default:
-        DEBUG ((DEBUG_INFO, "XhcInitializeEndpointContext64: Unknown EP found, Transfer ring is not allocated.\n"));
+        DEBUG ((
+          DEBUG_INFO,
+          "%a: %a found, Transfer ring is not allocated.\n",
+          __func__,
+          (EpType == USB_ENDPOINT_CONTROL ?
+           "Unsupported Control EP" :
+           "Unknown EP"
+           )
+          ));
         EpDesc = (USB_ENDPOINT_DESCRIPTOR *)((UINTN)EpDesc + EpDesc->Length);
         continue;
     }



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