1What are these headers ? 2------------------------ 3This is the canonical source of drm headers that user space should use for 4communicating with the kernel DRM subsystem. 5 6They flow from the kernel, thus any changes must be merged there first. 7Do _not_ attempt to "fix" these by deviating from the kernel ones ! 8 9 10Non-linux platforms - changes/patches 11------------------------------------- 12If your platform has local changes, please send them upstream for inclusion. 13Even if your patches don't get accepted in their current form, devs will 14give you feedback on how to address things properly. 15 16git send-email --subject-prefix="PATCH libdrm" your patches to dri-devel 17mailing list. 18 19Before doing so, please consider the following: 20 - Have the [libdrm vs kernel] headers on your platform deviated ? 21Consider unifying them first. 22 23 - Have you introduced additional ABI that's not available in Linux ? 24Propose it for [Linux kernel] upstream inclusion. 25If that doesn't work out (hopefully it never does), move it to another header 26and/or keep the change(s) local ? 27 28 - Are your changes DRI1/UMS specific ? 29There is virtually no interest/power in keeping those legacy interfaces. They 30are around due to the kernel "thou shalt not break existing user space" rule. 31 32Consider porting the driver to DRI2/KMS - all (almost?) sensible hardware is 33capable of supporting those. 34 35 36Which headers go where ? 37------------------------ 38A snipped from the, now removed, Makefile.am used to state: 39 40 XXX airlied says, nothing besides *_drm.h and drm*.h should be necessary. 41 however, r300 and via need their reg headers installed in order to build. 42 better solutions are welcome. 43 44Obviously the r300 and via headers are no longer around ;-) 45 46Reason behind is that the drm headers can be used as a basic communications 47channel with the respective kernel modules. If more advanced functionality is 48required one can pull the specific libdrm_$driver which is free to pull 49additional files from the kernel. 50 51For example: nouveau has nouveau/nvif/*.h while vc4 has vc4/*.h 52 53If your driver is still in prototyping/staging state, consider moving the 54$driver_drm.h into $driver and _not_ installing it. An header providing opaque 55definitions and access [via $driver_drmif.h or similar] would be better fit. 56 57 58When and which headers to update 59-------------------------------- 60Ideally all files will be synced (updated) with the latest released kernel on 61each libdrm release. Sadly that's not yet possible since quite a few headers 62differ significantly - see Outdated or Broken Headers section below. 63 64That said, it's up-to the individual developers to sync with newer version 65(from drm-next) as they see fit. 66 67 68When and how to update these files 69---------------------------------- 70Note: One should not do _any_ changes to the files apart from the steps below. 71 72In order to update the files do the following: 73 - Switch to a Linux kernel tree/branch which is not rebased. 74 For example: drm-next (https://cgit.freedesktop.org/drm/drm) 75 - Install the headers via `make headers_install' to a separate location. 76 - Copy the drm header[s] + git add + git commit. 77 - Note: Your commit message must include: 78 a) Brief summary on the delta. If there's any change that looks like an 79API/ABI break one _must_ explicitly state why it's safe to do so. 80 b) "Generated using make headers_install." 81 c) "Generated from $tree/branch commit $sha" 82 83 84Outdated or Broken Headers 85-------------------------- 86This section contains a list of headers and the respective "issues" they might 87have relative to their kernel equivalent. 88 89Most UMS headers: 90 - Not using fixed size integers - compat ioctls are broken. 91Status: ? 92Promote to fixed size ints, which match the current (32bit) ones. 93 94nouveau_drm.h 95 - Missing macros NOUVEAU_GETPARAM*, NOUVEAU_DRM_HEADER_PATCHLEVEL, structs, 96enums 97Status: Deliberate UABI choice; nouveau hides the exact kernel ABI behind libdrm 98 99r128_drm.h 100 - Broken compat ioctls. 101 102radeon_drm.h 103 - Missing RADEON_TILING_R600_NO_SCANOUT, CIK_TILE_MODE_*, broken UMS ioctls 104 - Both kernel and libdrm: missing padding - 105drm_radeon_gem_{create,{g,s}et_tiling,set_domain} others ? 106Status: ? 107 108savage_drm.h 109 - Renamed ioctls - DRM_IOCTL_SAVAGE_{,BCI}_EVENT_EMIT, compat ioctls are broken. 110Status: ? 111 112sis_drm.h 113 - Borken ioctls + libdrm uses int vs kernel long 114Status: ? 115 116via_drm.h 117 - Borken ioctls - libdrm int vs kernel long 118Status: ? 119 120 121omap_drm.h (living in $TOP/omap) 122 - License mismatch, missing DRM_IOCTL_OMAP_GEM_NEW and related struct 123Status: ? 124 125exynos_drm.h (living in $TOP/exynos) 126 - License mismatch, now using fixed size ints (but not everywhere). Lots of 127new stuff. 128Status: ? 129