Den 28.08.2017 23.58, skrev Daniel Vetter:
Hi Noralf,
On Mon, Aug 28, 2017 at 07:17:42PM +0200, Noralf Trønnes wrote:
This adds device unplug support to drm_fb_helper, drm_fb_cma_helper
(fbdev) and tinydrm.
My motivation for doing this is to make tinydrm useable with USB
devices. This discussion gave insight into the problem:
[PATCH v5 2/6] drm/bridge: Add a devm_ allocator for panel bridge.
https://lists.freedesktop.org/archives/dri-devel/2017-August/149376.html
Looks a lot less scary than I thought, but I think needs a bit more
polish.
I'm glad you made me look closer at unregister_framebuffer(), since it
did handle this quite good. I was fooled by the 2 usb fbdev drivers
that forked out unregistering to a worker.
I think it'd be also great if you could co-evolve the udl driver to get
this right, since it looks like right now it'll just oops when you unplug
when userspace is using the fbdev emulation. That way we'd be at least
somewhat consistent with unpluggable drivers, and since it's only 1 other
it should be doable. Unplugging is already hard, having 2 drivers do stuff
differently (when we only have 2 with unplug support) pretty much
guarnatees we'll never get this right.
I turns out that udl by default doesn't use fbdev mmap deferred io,
because it interferes with shmem's use of page->lru. This means that no
one uses it and since fbcon detaches itself on unregister_framebuffer(),
udl is in the clear with regards to fbdev.
In my shmem gem library I'll work around the page->lru issue by using a
shadow fbdev buffer. Since the library will have code from udl, I reckon
that udl can switch to using it.
Noralf.
But maybe good to first develop this using your own driver only.
Cheers, Daniel
Noralf.
Noralf Trønnes (6):
drm/fb-helper: Avoid NULL ptr dereference in fb_set_suspend()
drm/fb-helper: Support device unplug
drm/fb-cma-helper: Support device unplug
drm/tinydrm: Embed drm_device in tinydrm_device
drm/tinydrm/mi0283qt: Let the display pipe handle power
drm/tinydrm: Support device unplug
drivers/gpu/drm/drm_fb_cma_helper.c | 139 +++++++++----------
drivers/gpu/drm/drm_fb_helper.c | 207 +++++++++++++++++++++++++++-
drivers/gpu/drm/tinydrm/core/tinydrm-core.c | 109 ++++++++++-----
drivers/gpu/drm/tinydrm/core/tinydrm-pipe.c | 2 +-
drivers/gpu/drm/tinydrm/mi0283qt.c | 77 +++--------
drivers/gpu/drm/tinydrm/mipi-dbi.c | 27 ++--
drivers/gpu/drm/tinydrm/repaper.c | 19 ++-
drivers/gpu/drm/tinydrm/st7586.c | 25 ++--
include/drm/drm_fb_cma_helper.h | 1 +
include/drm/drm_fb_helper.h | 35 +++++
include/drm/tinydrm/tinydrm.h | 14 +-
11 files changed, 460 insertions(+), 195 deletions(-)
--
2.7.4
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