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linux-next/include/xen
Oleksandr Andrushchenko 8945c08e2b xen/displif: add ABI for para-virtual display
This is the ABI for the two halves of a para-virtualized
display driver.

This protocol aims to provide a unified protocol which fits more
sophisticated use-cases than a framebuffer device can handle. At the
moment basic functionality is supported with the intention to extend:
  o multiple dynamically allocated/destroyed framebuffers
  o buffers of arbitrary sizes
  o better configuration options including multiple display support

Note: existing fbif can be used together with displif running at the
same time, e.g. on Linux one provides framebuffer and another DRM/KMS

Future extensions to the existing protocol may include:
  o allow display/connector cloning
  o allow allocating objects other than display buffers
  o add planes/overlays support
  o support scaling
  o support rotation

Note, that this protocol doesn't use ring macros for
bi-directional exchange (PV calls/9pfs) bacause:
  o it statically defines the use of a single page
    for the ring buffer
  o it uses direct memory access to ring's contents
    w/o memory copying
  o re-uses the same idea that kbdif/fbif use
    which for this use-case seems to be appropriate

==================================================
Rationale for introducing this protocol instead of
using the existing fbif:
==================================================

1. In/out event sizes
  o fbif - 40 octets
  o displif - 40 octets
This is only the initial version of the displif protocol
which means that there could be requests which will not fit
(WRT introducing some GPU related functionality
later on). In that case we cannot alter fbif sizes as we need to
be backward compatible an will be forced to handle those
apart of fbif.

2. Shared page
Displif doesn't use anything like struct xenfb_page, but
DEFINE_RING_TYPES(xen_displif, struct xendispl_req, struct
xendispl_resp) which is a better and more common way.
Output events use a shared page which only has in_cons and in_prod
and all the rest is used for incoming events. Here struct xenfb_page
could probably be used as is despite the fact that it only has a half
of a page for incoming events which is only 50 events. (consider
something like 60Hz display)

3. Amount of changes.
fbif only provides XENFB_TYPE_UPDATE and XENFB_TYPE_RESIZE
events, so it looks like it is easier to get fb support into displif
than vice versa. displif at the moment has 6 requests and 1 event,
multiple connector support, etc.

Signed-off-by: Oleksandr Grytsov <oleksandr_grytsov@epam.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Acked-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
2017-05-02 11:13:09 +02:00
..
arm This is a tree wide change and has been kept separate for that reason. 2017-02-25 13:45:43 -08:00
interface xen/displif: add ABI for para-virtual display 2017-05-02 11:13:09 +02:00
acpi.h xen / ACPI: notify xen when reduced hardware sleep is available 2013-07-31 14:22:35 +02:00
balloon.h xen/balloon: use hotplugged pages for foreign mappings etc. 2015-10-23 14:20:05 +01:00
events.h xen/events: Support event channel rebind on ARM 2015-08-20 12:24:15 +01:00
features.h
grant_table.h xen/grant-table: Add an helper to iterate over a specific number of grants 2015-10-23 14:20:46 +01:00
hvc-console.h treewide: use __printf not __attribute__((format(printf,...))) 2011-10-31 17:30:54 -07:00
hvm.h xen: Convert printks to pr_<level> 2013-06-28 11:19:58 -04:00
page.h x86/boot/e820: Clean up the E820 table size define names 2017-01-28 22:55:23 +01:00
platform_pci.h xen/pvhvm: Remove the xen_platform_pci int. 2014-01-03 14:54:53 -05:00
swiotlb-xen.h swiotlb-xen: implement xen_swiotlb_get_sgtable callback 2017-02-13 14:15:12 -05:00
tmem.h xen: tmem: enable Xen tmem shim to be built/loaded as a module 2013-04-30 17:04:01 -07:00
xen-ops.h xen: create xen_create/destroy_contiguous_region() stubs for PVHVM only builds 2017-05-02 11:10:06 +02:00
xen.h xen/pvh: Bootstrap PVH guest 2017-02-07 08:07:01 -05:00
xenbus_dev.h xenbus: Add support for xenbus backend in stub domain 2012-05-21 09:53:18 -04:00
xenbus.h xen: modify xenstore watch event interface 2017-02-09 11:26:49 -05:00