linux-kernel - Re: [RFC][PATCH 2/5 v2] dma-buf: heaps: Add heap helpers

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Date:   Thu, 21 Mar 2019 13:11:02 -0700
From:   John Stultz <john.stultz@...aro.org>
To:     Brian Starkey <Brian.Starkey@....com>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Laura Abbott <labbott@...hat.com>,
        Benjamin Gaignard <benjamin.gaignard@...aro.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Liam Mark <lmark@...eaurora.org>,
        "Andrew F . Davis" <afd@...com>, Chenbo Feng <fengc@...gle.com>,
        Alistair Strachan <astrachan@...gle.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        nd <nd@....com>
Subject: Re: [RFC][PATCH 2/5 v2] dma-buf: heaps: Add heap helpers

On Tue, Mar 19, 2019 at 7:26 AM Brian Starkey <Brian.Starkey@....com> wrote:
>
> Hi John,
>
> On Tue, Mar 05, 2019 at 12:54:30PM -0800, John Stultz wrote:
>
> ...
>
> > +
> > +void dma_heap_buffer_destroy(struct dma_heap_buffer *heap_buffer)
> > +{
> > +     struct heap_helper_buffer *buffer = to_helper_buffer(heap_buffer);
> > +
> > +     if (buffer->kmap_cnt > 0) {
> > +             pr_warn_once("%s: buffer still mapped in the kernel\n",
> > +                          __func__);
>
> Could be worth something louder like a full WARN.
>
> > +             vunmap(buffer->vaddr);
> > +     }
> > +
> > +     buffer->free(buffer);
> > +}
> > +
>
> ...
>
> > +
> > +static void *dma_heap_dma_buf_kmap(struct dma_buf *dmabuf,
> > +                                     unsigned long offset)
> > +{
> > +     struct dma_heap_buffer *heap_buffer = dmabuf->priv;
> > +     struct heap_helper_buffer *buffer = to_helper_buffer(heap_buffer);
> > +
> > +     return buffer->vaddr + offset * PAGE_SIZE;
>
> I think it'd be good to check for NULL vaddr and return NULL in that
> case. Less chance of an invalid pointer being accidentally used then.

Thanks so much for the feedback! I've added these two suggestions in!
-john