Re: [Qemu-devel] [Qemu-ppc] [PATCH 2/2] Add Enhanced Three-Speed Ethernet Controller (eTSEC)

[Scott Wood]

On 07/19/2013 04:22:46 AM, Fabien Chouteau wrote:
> On 07/18/2013 10:37 PM, Scott Wood wrote:
> > On 07/18/2013 04:27:50 AM, Fabien Chouteau wrote:
> >> The BD is full, we will have to put the rest of padding in the  
> next one.
> >
> > What rest of padding?  I thought you said rx_padding was 2  
> somehow?  If that were true, then it would be zero at the end.
> >
>
> Read my description again.

OK, I was confused by your answering "yes" to "wouldn't *size be 2  
here" -- I thought it was clear from the context that I was talking  
about at the time of the "if (*size == etsec->rx_padding)" statement.   
Maybe you thought I was talking about what would happen at that  
if-statement in the next descriptor?

In any case, it's a bit hard to follow this code.  rx_fcb_size is  
included in to_write, but not in *size.  rx_padding is included in  
*size, but not in to_write.  And it generally makes me nervous to see  
code that will go into an infinite loop (or other odd behavior) unless  
an exact-equality terminating condition is met, especially when it's as  
complicated as this, without an assertion to check for the bad case  
(even if it looks like it could never happen).

-Scott