DRM's format-conversion helpers require temporary memory. Pass the buffer from the caller and keep it allocated over several calls. Allow the caller to preallocate the buffer memory. The motivation for this patchset is the recent work on a DRM panic handler. The panic handler requires format conversion to display an error to the screen. But allocating memory during kernel panics is fragile. The changes in this patchset enable the DRM panic handler to preallocate buffer storage before the panic occurs. As an additonal benefit, drivers can now keep the temporary storage across multiple display updates. Avoiding memory allocation reduces the CPU overhead of the format helpers. Patch 1 adds struct drm_xfrm_buf, a simple interface to pass around the buffer storage. Patch 2 moves the memory management from the format helpers into their callers. Drivers release the temporary storage at the end of their display-update functions. Patches 3 to 8 update three drivers to keep the allocated memory for all of a device's lifetime. Managed cleanup releases the buffer as part of releaseing the device. As additional benefit, buffer allocation now happens in atomic_check helpers. The driver thus detects OOM errors before the display update begins. Tested with simpledrm. v2: * reserve storage during probing in the drivers Thomas Zimmermann (5): drm/format-helper: Add struct drm_xfrm_buf to cache format conversion drm/format-helper: Pass xfrm buffer to format-conversion helpers drm/simpledrm: Store xfrm buffer in device instance drm/ofdrm: Store xfrm buffer in device instance drm/ssd130x: Store xfrm buffer in device instance drivers/gpu/drm/drm_format_helper.c | 204 +++++++++++++----- drivers/gpu/drm/drm_mipi_dbi.c | 7 +- drivers/gpu/drm/gud/gud_pipe.c | 21 +- drivers/gpu/drm/solomon/ssd130x.c | 16 +- drivers/gpu/drm/solomon/ssd130x.h | 3 + .../gpu/drm/tests/drm_format_helper_test.c | 33 +-- drivers/gpu/drm/tiny/cirrus.c | 5 +- drivers/gpu/drm/tiny/ofdrm.c | 11 +- drivers/gpu/drm/tiny/repaper.c | 5 +- drivers/gpu/drm/tiny/simpledrm.c | 11 +- drivers/gpu/drm/tiny/st7586.c | 5 +- include/drm/drm_format_helper.h | 74 +++++-- 12 files changed, 300 insertions(+), 95 deletions(-) -- 2.42.0
