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From: Brian Starkey <Brian.Starkey@arm.com>
To: "Andrew F. Davis" <afd@ti.com>
Cc: nd <nd@arm.com>, Chenbo Feng <fengc@google.com>,
	Alistair Strachan <astrachan@google.com>,
	Liam Mark <lmark@codeaurora.org>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>
Subject: Re: [EARLY RFC][PATCH] dma-buf: Add dma-buf heaps framework
Date: Tue, 5 Mar 2019 18:22:48 +0000	[thread overview]
Message-ID: <20190305182248.rgzdkemdpslfvfve@DESKTOP-E1NTVVP.localdomain> (raw)
In-Reply-To: <05f41d32-2a53-7116-691b-d3c843eae9d1@ti.com>

On Mon, Mar 04, 2019 at 08:53:42AM -0600, Andrew F. Davis wrote:
> On 3/1/19 6:06 AM, Brian Starkey wrote:
> > 
> > Am I right in thinking "cmd" comes from userspace? It might be a good
> > idea to not trust _IOC_SIZE(cmd) and use our own. I'm looking at
> > Documentation/ioctl/botching-up-ioctls.txt and drm_ioctl()
> > 
> 
> Yes cmd is from userspace, but we are in a switch-case that has already
> matched cmd == DMA_HEAP_IOC_ALLOC which is sized correctly.
> 

Ah yeah, sorry I missed that. It's fine until the struct gets
extended, which can be handled if/when.

[snip]

> > 
> > For me, the main thing that's missing is a way to unregister a heap.
> > If drivers/modules are registering heaps, then they also need to be
> > able to remove them again when they go away (rmmod or whatever).
> > 
> > I think that starts to be quite a can of worms, as you might end up
> > with buffers which outlive their allocator (that's true today as well
> > afaik, but is in drivers rather than something more central).
> > 
> 
> Yeah, was wanting to avoid dealing with all that, at least to start out
> with. At a high level memory shouldn't ever just disappear, we should
> block removing a heap driver until all buffers have been released.
> 

Correct me if I'm wrong, but I don't think there's a mechanism in the
kernel to do that right now is there? If my DRM driver registers a
heap, and then gets rmmod-ed, then kaboom. Just not exporting the
symbol might be OK to start with.

Thanks,
-Brian
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      parent reply	other threads:[~2019-03-05 18:22 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-25 14:36 [EARLY RFC][PATCH] dma-buf: Add dma-buf heaps framework Andrew F. Davis
2019-02-25 18:41 ` John Stultz
2019-02-26  0:20 ` John Stultz
2019-02-26 14:02   ` Andrew F. Davis
2019-02-26  0:55 ` John Stultz
2019-02-26 14:04   ` Andrew F. Davis
2019-02-26  3:53 ` Sumit Semwal
2019-02-26 14:28   ` Andrew F. Davis
2019-02-26  6:20 ` John Stultz
2019-02-26 14:46   ` Andrew F. Davis
2019-02-26 19:21     ` John Stultz
2019-02-26 23:40       ` John Stultz
2019-02-27 16:38         ` Andrew F. Davis
2019-02-27 21:55           ` John Stultz
2019-02-28 15:20             ` Andrew F. Davis
2019-03-01 23:49               ` John Stultz
2019-02-26 14:12 ` Benjamin Gaignard
2019-02-26 15:05   ` Andrew F. Davis
2019-02-26 15:22   ` Linus Walleij
2019-02-27 23:22 ` Laura Abbott
2019-02-28  0:14   ` John Stultz
2019-03-01 12:06 ` Brian Starkey
2019-03-04 14:53   ` Andrew F. Davis
2019-03-05  1:16     ` John Stultz
2019-03-05 18:05       ` Andrew F. Davis
2019-03-05 18:45         ` John Stultz
2019-03-05 18:22     ` Brian Starkey [this message]

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