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From: John Stultz <john.stultz@linaro.org>
To: Brian Starkey <Brian.Starkey@arm.com>
Cc: nd <nd@arm.com>, Alistair Strachan <astrachan@google.com>,
	Greg KH <gregkh@linuxfoundation.org>,
	Chenbo Feng <fengc@google.com>,
	lkml <linux-kernel@vger.kernel.org>,
	Liam Mark <lmark@codeaurora.org>, "Andrew F. Davis" <afd@ti.com>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>
Subject: Re: [RFC][PATCH 1/5 v2] dma-buf: Add dma-buf heaps framework
Date: Thu, 21 Mar 2019 14:16:34 -0700	[thread overview]
Message-ID: <CALAqxLUoXF-M1bGtDPLPg5qJ++e9gpjpnXrJ1_vHg1uLhWQDmA@mail.gmail.com> (raw)
In-Reply-To: <20190319120825.3mvdxp5saluboy7o@DESKTOP-E1NTVVP.localdomain>

On Tue, Mar 19, 2019 at 5:08 AM Brian Starkey <Brian.Starkey@arm.com> wrote:
>
> Hi John,
>
> On Tue, Mar 05, 2019 at 12:54:29PM -0800, John Stultz wrote:
> > From: "Andrew F. Davis" <afd@ti.com>
>
> [snip]
>
> > +
> > +#define NUM_HEAP_MINORS 128
> > +static DEFINE_IDR(dma_heap_idr);
> > +static DEFINE_MUTEX(minor_lock); /* Protect idr accesses */
>
> I saw that Matthew Wilcox is trying to nuke idr:
> https://patchwork.freedesktop.org/series/57073/
>
> Perhaps a different data structure could be considered? (I don't have
> an informed opinion on which).

Thanks for pointing this out! I've just switched to using the Xarray
implementation in my tree.

> > +static int dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
> > +                              unsigned int flags)
> > +{
> > +     len = PAGE_ALIGN(len);
> > +     if (!len)
> > +             return -EINVAL;
>
> I think aligning len to pages only makes sense if heaps are going to
> allocate aligned to pages too. Perhaps that's an implicit assumption?
> If so, lets document it.

I've added a comment as such (or do you have more thoughts on where it
should be documented?), and for consistency removed the PAGE_ALIGN
usage in the heap allocator hooks.

> Why not let the heaps take care of aligning len however they want
> though?

As Andrew already said, It seems page granularity would have to be the
finest allocation granularity for dmabufs.  If heaps want to implement
their own larger granularity alignment, I don't see any reason they
would be limited there.

And for me, its mostly because I stubbed my toe implementing the heap
code w/ the first patch that didn't have the page alignment in the
generic code. :)

> > +     /* Create device */
> > +     heap->heap_devt = MKDEV(MAJOR(dma_heap_devt), heap->minor);
> > +     dev_ret = device_create(dma_heap_class,
> > +                             NULL,
> > +                             heap->heap_devt,
> > +                             NULL,
> > +                             heap->name);
> > +     if (IS_ERR(dev_ret)) {
> > +             pr_err("dma_heap: Unable to create char device\n");
> > +             return PTR_ERR(dev_ret);
> > +     }
> > +
> > +     /* Add device */
> > +     cdev_init(&heap->heap_cdev, &dma_heap_fops);
> > +     ret = cdev_add(&heap->heap_cdev, dma_heap_devt, NUM_HEAP_MINORS);
>
> Shouldn't this be s/dma_heap_devt/heap->heap_devt/ and a count of 1?
>
> Also would it be better to have cdev_add/device_create the other way
> around? First create the char device, then once it's all set up
> register it with sysfs.

Thanks for catching that! Much appreciated! Reworked as suggested.

Though I realized last week I have not figured out a consistent way to
have the heaps show up in /dev/dma_heaps/<device> on both Android and
classic Linux environments.  I need to go stare at the /dev/input/
setup code some more.

> > +     if (ret < 0) {
> > +             device_destroy(dma_heap_class, heap->heap_devt);
> > +             pr_err("dma_heap: Unable to add char device\n");
> > +             return ret;
> > +     }
> > +
> > +     return 0;
> > +}
> > +EXPORT_SYMBOL(dma_heap_add);
>
> Until we've figured out how modules are going to work, I still think
> it would be a good idea to not export this.

Done!

thanks
-john
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  parent reply	other threads:[~2019-03-21 21:16 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-03-05 20:54 [RFC][PATCH 0/5 v2] DMA-BUF Heaps (destaging ION) John Stultz
2019-03-05 20:54 ` [RFC][PATCH 1/5 v2] dma-buf: Add dma-buf heaps framework John Stultz
2019-03-06 16:12   ` Benjamin Gaignard
2019-03-06 16:57     ` John Stultz
2019-03-15  8:55     ` Christoph Hellwig
2019-03-06 16:27   ` Andrew F. Davis
2019-03-06 19:03     ` John Stultz
2019-03-06 21:45       ` Andrew F. Davis
2019-03-15  8:54   ` Christoph Hellwig
2019-03-15 20:24     ` Andrew F. Davis
2019-03-15 20:18   ` Laura Abbott
2019-03-15 20:49     ` Andrew F. Davis
2019-03-15 21:29     ` John Stultz
2019-03-15 22:44       ` Laura Abbott
2019-03-18  4:38         ` Sumit Semwal
2019-03-18  4:41         ` Sumit Semwal
2019-03-19 12:08   ` Brian Starkey
2019-03-19 15:24     ` Andrew F. Davis
2019-03-21 21:16     ` John Stultz [this message]
2019-03-27 14:53   ` Greg KH
2019-03-28  6:09     ` John Stultz
2019-03-05 20:54 ` [RFC][PATCH 2/5 v2] dma-buf: heaps: Add heap helpers John Stultz
2019-03-13 20:18   ` Liam Mark
2019-03-13 21:48     ` Andrew F. Davis
2019-03-13 22:57       ` Liam Mark
2019-03-13 23:42         ` Andrew F. Davis
2019-03-15  9:06   ` Christoph Hellwig
2019-03-19 15:03     ` Andrew F. Davis
2019-03-21 20:01     ` John Stultz
2019-03-19 14:26   ` Brian Starkey
2019-03-21 20:11     ` John Stultz
2019-03-21 20:35     ` Andrew F. Davis
2019-03-21 20:43   ` Andrew F. Davis
2019-03-05 20:54 ` [RFC][PATCH 3/5 v2] dma-buf: heaps: Add system heap to dmabuf heaps John Stultz
2019-03-06 16:01   ` Benjamin Gaignard
2019-03-11  5:48     ` John Stultz
2019-03-13 20:20   ` Liam Mark
2019-03-13 22:49     ` John Stultz
2019-03-15  9:06   ` Christoph Hellwig
2019-03-05 20:54 ` [RFC][PATCH 4/5 v2] dma-buf: heaps: Add CMA heap to dmabuf heapss John Stultz
2019-03-06 16:05   ` Benjamin Gaignard
2019-03-21 20:15     ` John Stultz
2019-03-15  9:06   ` Christoph Hellwig
2019-03-15 20:08     ` John Stultz
2019-03-19 14:53   ` Brian Starkey
2019-03-05 20:54 ` [RFC][PATCH 5/5 v2] kselftests: Add dma-heap test John Stultz
2019-03-06 16:14   ` Benjamin Gaignard
2019-03-06 16:35     ` Andrew F. Davis
2019-03-06 18:19       ` John Stultz
2019-03-06 18:32         ` Andrew F. Davis
2019-03-06 17:01     ` John Stultz
2019-03-15 20:07       ` Laura Abbott
2019-03-15 20:13         ` John Stultz
2019-03-15 20:49           ` Laura Abbott
2019-03-13 20:23   ` Liam Mark
2019-03-13 20:11 ` [RFC][PATCH 0/5 v2] DMA-BUF Heaps (destaging ION) Liam Mark
2019-03-13 22:30   ` John Stultz
2019-03-13 23:29     ` Liam Mark
2019-03-19 16:54     ` Benjamin Gaignard
2019-03-19 16:59       ` Andrew F. Davis
2019-03-19 21:58         ` Rob Clark
2019-03-19 22:36           ` John Stultz
2019-03-20  9:16             ` Benjamin Gaignard
2019-03-20 14:44               ` Andrew F. Davis
2019-03-20 15:59                 ` Benjamin Gaignard
2019-03-20 16:11               ` John Stultz
2019-03-15 20:34 ` Laura Abbott
2019-03-15 23:15 ` Jerome Glisse
2019-03-16  0:16   ` John Stultz

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