[PATCH] ARM: Tegra: DMA: Fail safe if initialization fails

[Stephen Warren]

Colin Cross wrote at Wednesday, February 23, 2011 10:38 AM:
> 
> On Wed, Feb 23, 2011 at 9:29 AM, Stephen Warren <swarren at nvidia.com> wrote:
> > tegra_dma_init currently simply bails out early if any initialization fails.
> > This skips various data-structure initialization. In turn, this means that
> > tegra_dma_allocate_channel can still hand out channels. In this case, when
> > tegra_dma_free_channel is called, which calls tegra_dma_cancel, the walking
> > on ch->list will OOPS since the list's next/prev pointers may still be
> > NULL.
> >
> > To solve this:
> > * Mark all possible channels as in-use before doing anything else in init.
> > * Only mark a channel as free once all channel-related initialization has
> >  completed.
> >
> > This prevents allocate_channel from handing out uninitialized channels.
> >
> > There is still one small hole; allocate_channel can't check the usage array
> > for the shared channel, since this channel is permanently marked in-use.
> > This could be solved using an explicit "init OK" flag that allocate_channel
> > could check.
>
> If we still need an init complete flag, why not skip this patch and
> just add that?

I tend to like the cleanup in this patch; it simplifies the channel_usage
initialization. I'll let you make the call on whether to take this or not.

I can certainly throw together a second patch, or modify this patch, to also
use an init_ok flag to completely solve the shared channel case too though.

-- 
nvpublic