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Diffstat (limited to 'Documentation/gpu/todo.rst')
| -rw-r--r-- | Documentation/gpu/todo.rst | 104 |
1 files changed, 68 insertions, 36 deletions
diff --git a/Documentation/gpu/todo.rst b/Documentation/gpu/todo.rst index 513b20ccef1e..393d218e4a0c 100644 --- a/Documentation/gpu/todo.rst +++ b/Documentation/gpu/todo.rst @@ -322,18 +322,6 @@ Contact: Daniel Vetter, Noralf Tronnes Level: Advanced -idr_init_base() ---------------- - -DRM core&drivers uses a lot of idr (integer lookup directories) for mapping -userspace IDs to internal objects, and in most places ID=0 means NULL and hence -is never used. Switching to idr_init_base() for these would make the idr more -efficient. - -Contact: Daniel Vetter - -Level: Starter - struct drm_gem_object_funcs --------------------------- @@ -343,19 +331,6 @@ converted, except for struct drm_driver.gem_prime_mmap. Level: Intermediate -Rename CMA helpers to DMA helpers ---------------------------------- - -CMA (standing for contiguous memory allocator) is really a bit an accident of -what these were used for first, a much better name would be DMA helpers. In the -text these should even be called coherent DMA memory helpers (so maybe CDM, but -no one knows what that means) since underneath they just use dma_alloc_coherent. - -Contact: Laurent Pinchart, Daniel Vetter - -Level: Intermediate (mostly because it is a huge tasks without good partial -milestones, not technically itself that challenging) - connector register/unregister fixes ----------------------------------- @@ -617,17 +592,6 @@ Contact: Javier Martinez Canillas <javierm@redhat.com> Level: Intermediate -Convert Kernel Selftests (kselftest) to KUnit tests when appropriate --------------------------------------------------------------------- - -Many of the `Kselftest <https://www.kernel.org/doc/html/latest/dev-tools/kselftest.html>`_ -tests in DRM could be converted to Kunit tests instead, since that framework -is more suitable for unit testing. - -Contact: Javier Martinez Canillas <javierm@redhat.com> - -Level: Starter - Enable trinity for DRM ---------------------- @@ -715,6 +679,74 @@ Contact: Sam Ravnborg Level: Advanced +Brightness handling on devices with multiple internal panels +============================================================ + +On x86/ACPI devices there can be multiple backlight firmware interfaces: +(ACPI) video, vendor specific and others. As well as direct/native (PWM) +register programming by the KMS driver. + +To deal with this backlight drivers used on x86/ACPI call +acpi_video_get_backlight_type() which has heuristics (+quirks) to select +which backlight interface to use; and backlight drivers which do not match +the returned type will not register themselves, so that only one backlight +device gets registered (in a single GPU setup, see below). + +At the moment this more or less assumes that there will only +be 1 (internal) panel on a system. + +On systems with 2 panels this may be a problem, depending on +what interface acpi_video_get_backlight_type() selects: + +1. native: in this case the KMS driver is expected to know which backlight + device belongs to which output so everything should just work. +2. video: this does support controlling multiple backlights, but some work + will need to be done to get the output <-> backlight device mapping + +The above assumes both panels will require the same backlight interface type. +Things will break on systems with multiple panels where the 2 panels need +a different type of control. E.g. one panel needs ACPI video backlight control, +where as the other is using native backlight control. Currently in this case +only one of the 2 required backlight devices will get registered, based on +the acpi_video_get_backlight_type() return value. + +If this (theoretical) case ever shows up, then supporting this will need some +work. A possible solution here would be to pass a device and connector-name +to acpi_video_get_backlight_type() so that it can deal with this. + +Note in a way we already have a case where userspace sees 2 panels, +in dual GPU laptop setups with a mux. On those systems we may see +either 2 native backlight devices; or 2 native backlight devices. + +Userspace already has code to deal with this by detecting if the related +panel is active (iow which way the mux between the GPU and the panels +points) and then uses that backlight device. Userspace here very much +assumes a single panel though. It picks only 1 of the 2 backlight devices +and then only uses that one. + +Note that all userspace code (that I know off) is currently hardcoded +to assume a single panel. + +Before the recent changes to not register multiple (e.g. video + native) +/sys/class/backlight devices for a single panel (on a single GPU laptop), +userspace would see multiple backlight devices all controlling the same +backlight. + +To deal with this userspace had to always picks one preferred device under +/sys/class/backlight and will ignore the others. So to support brightness +control on multiple panels userspace will need to be updated too. + +There are plans to allow brightness control through the KMS API by adding +a "display brightness" property to drm_connector objects for panels. This +solves a number of issues with the /sys/class/backlight API, including not +being able to map a sysfs backlight device to a specific connector. Any +userspace changes to add support for brightness control on devices with +multiple panels really should build on top of this new KMS property. + +Contact: Hans de Goede + +Level: Advanced + Outside DRM =========== |