Re: [PATCH] pci_dma_rw: return correct value instead of 0

[Stefano Garzarella <sgarzare@redhat.com>]

On Thu, Jul 30, 2020 at 10:50:43AM +0200, Emanuele Giuseppe Esposito wrote:
> 
> 
> On 30/07/2020 09:41, Stefano Garzarella wrote:
> > On Thu, Jul 30, 2020 at 12:17:32AM +0200, Emanuele Giuseppe Esposito wrote:
> > > pci_dma_rw currently always returns 0, regardless
> > > of the result of dma_memory_rw. Adjusted to return
> > > the correct value.
> > > 
> > > Signed-off-by: Emanuele Giuseppe Esposito <e.emanuelegiuseppe@gmail.com>
> > > ---
> > >   include/hw/pci/pci.h | 3 +--
> > >   1 file changed, 1 insertion(+), 2 deletions(-)
> > > 
> > > diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
> > > index c1bf7d5356..41c4ab5932 100644
> > > --- a/include/hw/pci/pci.h
> > > +++ b/include/hw/pci/pci.h
> > > @@ -787,8 +787,7 @@ static inline AddressSpace *pci_get_address_space(PCIDevice *dev)
> > >   static inline int pci_dma_rw(PCIDevice *dev, dma_addr_t addr,
> > >                                void *buf, dma_addr_t len, DMADirection dir)
> > >   {
> > > -    dma_memory_rw(pci_get_address_space(dev), addr, buf, len, dir);
> > > -    return 0;
> > > +    return dma_memory_rw(pci_get_address_space(dev), addr, buf, len, dir);
> > >   }
> > 
> > I think it's a left over from when we used "void cpu_physical_memory_rw()".
> > 
> > I agree that it is better to return the dma_memory_rw() return value, but
> > at first look, no one seems to check the return value of pci_dma_rw(),
> > pci_dma_read(), andpci_dma_write().
> > 
> > Should we make them void?
> 
> I noticed that nobody checks the return of those functions, but I think
> checking for possible error is always useful. I am using the edu device and
> clearly doing something wrong since with this fix I discovered that the
> pci_dma_read call returns nonzero.
> 
> Keeping the function as it is or void would make it harder to spot such
> errors in future.

I agree, I was just worried that no one checks the return value.

Thanks,
Stefano