Re: [PATCH 24/25] dmaengine: dw-edma: Skip cleanup procedure if no private data found

Manivannan Sadhasivam
2022-04-23T14:45:23Z

On Mon, Apr 18, 2022 at 04:48:33PM +0300, Serge Semin wrote:
> On Fri, Mar 25, 2022 at 11:45:03PM +0530, Manivannan Sadhasivam wrote:
> > On Thu, Mar 24, 2022 at 04:48:35AM +0300, Serge Semin wrote:
> > > DW eDMA driver private data is preserved in the passed DW eDMA chip info
> > > structure. If either probe procedure failed or for some reason the passed
> > > info object doesn't have private data pointer initialized we need to halt
> > > the DMA device cleanup procedure in order to prevent possible system
> > > crashes.
> > >
> >
>
> > How come remove() could happen when probe() failed? If you hit this issue then
> > something else is utterly going wrong.
>
> It fully depends on the DW eDMA client driver implementation, which
> can't and in general shouldn't be guessed. But what must be done in
> the DW eDMA driver is a protection against the invalid data being
> passed to the exported API methods. That wrong situation must be
> detected and handled in the API user code. It's much easier to do by
> having an error code returned from the dw_edma_remove() method than
> catching random system crashes.
>

Even though I don't see any practical issue, I'm fine with this.

Thanks,
Mani

> -Sergey
>
> >
> > Thanks,
> > Mani
> >
> > > Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
> > > ---
> > > drivers/dma/dw-edma/dw-edma-core.c | 4 ++++
> > > 1 file changed, 4 insertions(+)
> > >
> > > diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> > > index ca5cd7c99571..b932682a8ba8 100644
> > > --- a/drivers/dma/dw-edma/dw-edma-core.c
> > > +++ b/drivers/dma/dw-edma/dw-edma-core.c
> > > @@ -1030,6 +1030,10 @@ int dw_edma_remove(struct dw_edma_chip *chip)
> > > struct dw_edma *dw = chip->dw;
> > > int i;
> > >
> > > + /* Skip removal if no private data found */
> > > + if (!dw)
> > > + return -ENODEV;
> > > +
> > > /* Disable eDMA */
> > > dw_edma_v0_core_off(dw);
> > >
> > > --
> > > 2.35.1
> > >