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7392f2459e
The conversion functions drm_fb_xrgb8888_to_mono() and
drm_fb_gray8_to_mono_line() do not behave correctly when the
horizontal boundaries of the clip rectangle are not multiples of 8:
a. When x1 % 8 != 0, the calculated pitch is not correct,
b. When x2 % 8 != 0, the pixel data for the last byte is wrong.
Simplify the code and fix (a) by:
1. Removing start_offset, and always storing the first pixel in the
first bit of the monochrome destination buffer.
Drivers that require the first pixel in a byte to be located at an
x-coordinate that is a multiple of 8 can always align the clip
rectangle before calling drm_fb_xrgb8888_to_mono().
Note that:
- The ssd130x driver does not need the alignment, as the
monochrome buffer is a temporary format,
- The repaper driver always updates the full screen, so the clip
rectangle is always aligned.
2. Passing the number of pixels to drm_fb_gray8_to_mono_line(),
instead of the number of bytes, and the number of pixels in the
last byte.
Fix (b) by explicitly setting the target bit, instead of always setting
bit 7 and shifting the value in each loop iteration.
Remove the bogus pitch check, which operates on bytes instead of pixels,
and triggers when e.g. flashing the cursor on a text console with a font
that is 8 pixels wide.
Drop the confusing comment about scanlines, as a pitch in bytes always
contains a multiple of 8 pixels.
While at it, use the drm_rect_height() helper instead of open-coding the
same operation.
Update the comments accordingly.
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.