fb24aaf541
Add drm_modes_size_dumb(), a helper to calculate the dumb-buffer scanline pitch and allocation size. Implementations of struct drm_driver.dumb_create can call the new helper for their size computations. There is currently quite a bit of code duplication among DRM's memory managers. Each calculates scanline pitch and buffer size from the given arguments, but the implementations are inconsistent in how they treat alignment and format support. Later patches will unify this code on top of drm_mode_size_dumb() as much as possible. drm_mode_size_dumb() uses existing 4CC format helpers to interpret the given color mode. This makes the dumb-buffer interface behave similar the kernel's video= parameter. Current per-driver implementations again likely have subtle differences or bugs in how they support color modes. The dumb-buffer UAPI is only specified for known color modes. These values describe linear, single-plane RGB color formats or legacy index formats. Other values should not be specified. But some user space still does. So for unknown color modes, there are a number of known exceptions for which drm_mode_size_dumb() calculates the pitch from the bpp value, as before. All other values work the same but print an error. v6: - document additional use cases for DUMB_CREATE2 in TODO list (Tomi) - fix typos in documentation (Tomi) v5: - check for overflows with check_mul_overflow() (Tomi) v4: - use %u conversion specifier (Geert) - list DRM_FORMAT_Dn in UAPI docs (Geert) - avoid dmesg spamming with drm_warn_once() (Sima) - add more information about bpp special case (Sima) - clarify parameters for hardware alignment - add a TODO item for DUMB_CREATE2 v3: - document the UAPI semantics - compute scanline pitch from for unknown color modes (Andy, Tomi) Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> Reviewed-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com> Link: https://lore.kernel.org/r/20250821081918.79786-3-tzimmermann@suse.de
15 lines
325 B
C
15 lines
325 B
C
/* SPDX-License-Identifier: MIT */
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#ifndef __DRM_DUMB_BUFFERS_H__
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#define __DRM_DUMB_BUFFERS_H__
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struct drm_device;
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struct drm_mode_create_dumb;
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int drm_mode_size_dumb(struct drm_device *dev,
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struct drm_mode_create_dumb *args,
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unsigned long hw_pitch_align,
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unsigned long hw_size_align);
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#endif
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