kernel.git/drivers/video/fbdev/metronomefb.c, branch linux-5.18.y

fbdev: Don't sort deferred-I/O pages by default

2022-02-16T15:41:45Z

Fbdev's deferred I/O sorts all dirty pages by default, which incurs a significant overhead. Make the sorting step optional and update the few drivers that require it. Use a FIFO list by default. Most fbdev drivers with deferred I/O build a bounding rectangle around the dirty pages or simply flush the whole screen. The only two affected DRM drivers, generic fbdev and vmwgfx, both use a bounding rectangle. In those cases, the exact order of the pages doesn't matter. The other drivers look at the page index or handle pages one-by-one. The patch sets the sort_pagelist flag for those, even though some of them would probably work correctly without sorting. Driver maintainers should update their driver accordingly. Sorting pages by memory offset for deferred I/O performs an implicit bubble-sort step on the list of dirty pages. The algorithm goes through the list of dirty pages and inserts each new page according to its index field. Even worse, list traversal always starts at the first entry. As video memory is most likely updated scanline by scanline, the algorithm traverses through the complete list for each updated page. For example, with 1024x768x32bpp each page covers exactly one scanline. Writing a single screen update from top to bottom requires updating 768 pages. With an average list length of 384 entries, a screen update creates (768 * 384 =) 294912 compare operation. Fix this by making the sorting step opt-in and update the few drivers that require it. All other drivers work with unsorted page lists. Pages are appended to the list. Therefore, in the common case of writing the framebuffer top to bottom, pages are still sorted by offset, which may have a positive effect on performance. Playing a video [1] in mplayer's benchmark mode shows the difference (i7-4790, FullHD, simpledrm, kernel with debugging). mplayer -benchmark -nosound -vo fbdev ./big_buck_bunny_720p_stereo.ogg With sorted page lists: BENCHMARKs: VC: 32.960s VO: 73.068s A: 0.000s Sys: 2.413s = 108.441s BENCHMARK%: VC: 30.3947% VO: 67.3802% A: 0.0000% Sys: 2.2251% = 100.0000% With unsorted page lists: BENCHMARKs: VC: 31.005s VO: 42.889s A: 0.000s Sys: 2.256s = 76.150s BENCHMARK%: VC: 40.7156% VO: 56.3219% A: 0.0000% Sys: 2.9625% = 100.0000% VC shows the overhead of video decoding, VO shows the overhead of the video output. Using unsorted page lists reduces the benchmark's run time by ~32s/~25%. v2: * Make sorted pagelists the special case (Sam) * Comment on drivers' use of pagelist (Sam) * Warn about the overhead in comment Signed-off-by: Thomas Zimmermann Acked-by: Sam Ravnborg Acked-by: Andy Shevchenko Link: https://download.blender.org/peach/bigbuckbunny_movies/big_buck_bunny_720p_stereo.ogg # [1] Link: https://patchwork.freedesktop.org/patch/msgid/20220211094640.21632-3-tzimmermann@suse.de

video: fbdev: Replace HTTP links with HTTPS ones

2020-07-20T09:47:29Z

Rationale: Reduces attack surface on kernel devs opening the links for MITM as HTTPS traffic is much harder to manipulate. Deterministic algorithm: For each file: If not .svg: For each line: If doesn't contain `\bxmlns\b`: For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`: If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`: If both the HTTP and HTTPS versions return 200 OK and serve the same content: Replace HTTP with HTTPS. Signed-off-by: Alexander A. Klimov Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20200719203714.61745-1-grandmaster@al2klimov.de

video: constify fb ops across all drivers

2019-12-05T08:57:53Z

Now that the fbops member of struct fb_info is const, we can start making the ops const as well. This does not cover all drivers; some actually modify the fbops struct, for example to adjust for different configurations, and others do more involved things that I'd rather not touch in practically obsolete drivers. Mostly this is the low hanging fruit where we can add "const" and be done with it. v3: - un-constify atyfb, mb862xx, nvidia and uvesabf (0day) v2: - fix typo (Christophe de Dinechin) - use "static const" instead of "const static" in mx3fb.c - also constify smscufx.c Cc: linux-fbdev@vger.kernel.org Reviewed-by: Daniel Vetter Signed-off-by: Jani Nikula Link: https://patchwork.freedesktop.org/patch/msgid/ce67f14435f3af498f2e8bf35ce4be11f7504132.1575390740.git.jani.nikula@intel.com

video: fbdev: metronomefb: fix some off by one bugs

2018-07-24T17:11:26Z

The "mem" buffer has "size" bytes. The ">" should be ">=" to prevent reading one character beyond the end of the array. Signed-off-by: Dan Carpenter Signed-off-by: Bartlomiej Zolnierkiewicz

lib/vsprintf.c: remove %Z support

2017-02-28T02:43:47Z

Now that %z is standartised in C99 there is no reason to support %Z. Unlike %L it doesn't even make format strings smaller. Use BUILD_BUG_ON in a couple ATM drivers. In case anyone didn't notice lib/vsprintf.o is about half of SLUB which is in my opinion is quite an achievement. Hopefully this patch inspires someone else to trim vsprintf.c more. Link: http://lkml.kernel.org/r/20170103230126.GA30170@avx2 Signed-off-by: Alexey Dobriyan Cc: Andy Shevchenko Cc: Rasmus Villemoes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

video: fbdev: metronomefb: two harmless off by one bugs

2016-02-16T12:52:43Z

par->metromem_cmd->args[] is an array of 31 elements of size u16. Here we have initialized the first "i" elements and want to set the rest to zero. The issue here is that ARRAY_SIZE(par->metromem_cmd->args) is 31 and not 32 as in the original code. It means that we set ->csum to zero, but that is harmless because we immediately set it to the correct value on the next line. Still, the buffer overflow upsets static checkers so let's correct the math. Signed-off-by: Dan Carpenter Signed-off-by: Tomi Valkeinen

video: fbdev: drop owner assignment from platform_drivers

2014-10-20T14:21:51Z

A platform_driver does not need to set an owner, it will be populated by the driver core. Signed-off-by: Wolfram Sang

video: move fbdev to drivers/video/fbdev

2014-04-17T05:10:19Z

The drivers/video directory is a mess. It contains generic video related files, directories for backlight, console, linux logo, lots of fbdev device drivers, fbdev framework files. Make some order into the chaos by creating drivers/video/fbdev directory, and move all fbdev related files there. No functionality is changed, although I guess it is possible that some subtle Makefile build order related issue could be created by this patch. Signed-off-by: Tomi Valkeinen Acked-by: Laurent Pinchart Acked-by: Geert Uytterhoeven Acked-by: Rob Clark Acked-by: Jingoo Han Acked-by: Daniel Vetter