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ab42b818 | 1 | ========================================================== |
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2 | uvesafb - A Generic Driver for VBE2+ compliant video cards |
3 | ========================================================== | |
4 | ||
5 | 1. Requirements | |
6 | --------------- | |
7 | ||
8 | uvesafb should work with any video card that has a Video BIOS compliant | |
9 | with the VBE 2.0 standard. | |
10 | ||
11 | Unlike other drivers, uvesafb makes use of a userspace helper called | |
12 | v86d. v86d is used to run the x86 Video BIOS code in a simulated and | |
13 | controlled environment. This allows uvesafb to function on arches other | |
14 | than x86. Check the v86d documentation for a list of currently supported | |
15 | arches. | |
16 | ||
17 | v86d source code can be downloaded from the following website: | |
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18 | |
19 | https://github.com/mjanusz/v86d | |
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20 | |
21 | Please refer to the v86d documentation for detailed configuration and | |
22 | installation instructions. | |
23 | ||
24 | Note that the v86d userspace helper has to be available at all times in | |
25 | order for uvesafb to work properly. If you want to use uvesafb during | |
26 | early boot, you will have to include v86d into an initramfs image, and | |
27 | either compile it into the kernel or use it as an initrd. | |
28 | ||
29 | 2. Caveats and limitations | |
30 | -------------------------- | |
31 | ||
32 | uvesafb is a _generic_ driver which supports a wide variety of video | |
33 | cards, but which is ultimately limited by the Video BIOS interface. | |
34 | The most important limitations are: | |
35 | ||
36 | - Lack of any type of acceleration. | |
37 | - A strict and limited set of supported video modes. Often the native | |
38 | or most optimal resolution/refresh rate for your setup will not work | |
39 | with uvesafb, simply because the Video BIOS doesn't support the | |
40 | video mode you want to use. This can be especially painful with | |
41 | widescreen panels, where native video modes don't have the 4:3 aspect | |
42 | ratio, which is what most BIOS-es are limited to. | |
43 | - Adjusting the refresh rate is only possible with a VBE 3.0 compliant | |
44 | Video BIOS. Note that many nVidia Video BIOS-es claim to be VBE 3.0 | |
45 | compliant, while they simply ignore any refresh rate settings. | |
46 | ||
47 | 3. Configuration | |
48 | ---------------- | |
49 | ||
50 | uvesafb can be compiled either as a module, or directly into the kernel. | |
51 | In both cases it supports the same set of configuration options, which | |
ab42b818 | 52 | are either given on the kernel command line or as module parameters, e.g.:: |
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53 | |
54 | video=uvesafb:1024x768-32,mtrr:3,ywrap (compiled into the kernel) | |
55 | ||
c0dd504c | 56 | # modprobe uvesafb mode_option=1024x768-32 mtrr=3 scroll=ywrap (module) |
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57 | |
58 | Accepted options: | |
59 | ||
ab42b818 | 60 | ======= ========================================================= |
0a0b53f6 | 61 | ypan Enable display panning using the VESA protected mode |
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62 | interface. The visible screen is just a window of the |
63 | video memory, console scrolling is done by changing the | |
64 | start of the window. This option is available on x86 | |
65 | only and is the default option on that architecture. | |
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66 | |
67 | ywrap Same as ypan, but assumes your gfx board can wrap-around | |
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68 | the video memory (i.e. starts reading from top if it |
69 | reaches the end of video memory). Faster than ypan. | |
70 | Available on x86 only. | |
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71 | |
72 | redraw Scroll by redrawing the affected part of the screen, this | |
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73 | is the default on non-x86. |
74 | ======= ========================================================= | |
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75 | |
76 | (If you're using uvesafb as a module, the above three options are | |
ab42b818 | 77 | used a parameter of the scroll option, e.g. scroll=ypan.) |
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79 | =========== ==================================================================== |
80 | vgapal Use the standard VGA registers for palette changes. | |
0a0b53f6 | 81 | |
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82 | pmipal Use the protected mode interface for palette changes. |
83 | This is the default if the protected mode interface is | |
84 | available. Available on x86 only. | |
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86 | mtrr:n Setup memory type range registers for the framebuffer |
87 | where n: | |
63e28a7a | 88 | |
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89 | - 0 - disabled (equivalent to nomtrr) |
90 | - 3 - write-combining (default) | |
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92 | Values other than 0 and 3 will result in a warning and will be |
93 | treated just like 3. | |
94 | ||
95 | nomtrr Do not use memory type range registers. | |
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96 | |
97 | vremap:n | |
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98 | Remap 'n' MiB of video RAM. If 0 or not specified, remap memory |
99 | according to video mode. | |
100 | ||
101 | vtotal:n If the video BIOS of your card incorrectly determines the total | |
102 | amount of video RAM, use this option to override the BIOS (in MiB). | |
103 | ||
104 | <mode> The mode you want to set, in the standard modedb format. Refer to | |
105 | modedb.txt for a detailed description. When uvesafb is compiled as | |
106 | a module, the mode string should be provided as a value of the | |
107 | 'mode_option' option. | |
108 | ||
109 | vbemode:x Force the use of VBE mode x. The mode will only be set if it's | |
110 | found in the VBE-provided list of supported modes. | |
111 | NOTE: The mode number 'x' should be specified in VESA mode number | |
112 | notation, not the Linux kernel one (eg. 257 instead of 769). | |
113 | HINT: If you use this option because normal <mode> parameter does | |
114 | not work for you and you use a X server, you'll probably want to | |
115 | set the 'nocrtc' option to ensure that the video mode is properly | |
116 | restored after console <-> X switches. | |
117 | ||
118 | nocrtc Do not use CRTC timings while setting the video mode. This option | |
119 | has any effect only if the Video BIOS is VBE 3.0 compliant. Use it | |
120 | if you have problems with modes set the standard way. Note that | |
121 | using this option implies that any refresh rate adjustments will | |
122 | be ignored and the refresh rate will stay at your BIOS default | |
123 | (60 Hz). | |
124 | ||
125 | noedid Do not try to fetch and use EDID-provided modes. | |
126 | ||
127 | noblank Disable hardware blanking. | |
128 | ||
129 | v86d:path Set path to the v86d executable. This option is only available as | |
130 | a module parameter, and not as a part of the video= string. If you | |
131 | need to use it and have uvesafb built into the kernel, use | |
132 | uvesafb.v86d="path". | |
133 | =========== ==================================================================== | |
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134 | |
135 | Additionally, the following parameters may be provided. They all override the | |
136 | EDID-provided values and BIOS defaults. Refer to your monitor's specs to get | |
137 | the correct values for maxhf, maxvf and maxclk for your hardware. | |
138 | ||
ab42b818 | 139 | =========== ====================================== |
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140 | maxhf:n Maximum horizontal frequency (in kHz). |
141 | maxvf:n Maximum vertical frequency (in Hz). | |
142 | maxclk:n Maximum pixel clock (in MHz). | |
ab42b818 | 143 | =========== ====================================== |
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144 | |
145 | 4. The sysfs interface | |
146 | ---------------------- | |
147 | ||
148 | uvesafb provides several sysfs nodes for configurable parameters and | |
149 | additional information. | |
150 | ||
151 | Driver attributes: | |
152 | ||
153 | /sys/bus/platform/drivers/uvesafb | |
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154 | v86d |
155 | (default: /sbin/v86d) | |
156 | ||
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157 | Path to the v86d executable. v86d is started by uvesafb |
158 | if an instance of the daemon isn't already running. | |
159 | ||
160 | Device attributes: | |
161 | ||
162 | /sys/bus/platform/drivers/uvesafb/uvesafb.0 | |
ab42b818 | 163 | nocrtc |
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164 | Use the default refresh rate (60 Hz) if set to 1. |
165 | ||
ab42b818 | 166 | oem_product_name, oem_product_rev, oem_string, oem_vendor |
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167 | Information about the card and its maker. |
168 | ||
ab42b818 | 169 | vbe_modes |
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170 | A list of video modes supported by the Video BIOS along with their |
171 | VBE mode numbers in hex. | |
172 | ||
ab42b818 | 173 | vbe_version |
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174 | A BCD value indicating the implemented VBE standard. |
175 | ||
176 | 5. Miscellaneous | |
177 | ---------------- | |
178 | ||
179 | Uvesafb will set a video mode with the default refresh rate and timings | |
180 | from the Video BIOS if you set pixclock to 0 in fb_var_screeninfo. | |
181 | ||
182 | ||
ab42b818 | 183 | |
0a0b53f6 | 184 | Michal Januszewski <spock@gentoo.org> |
ab42b818 | 185 | |
676709b1 | 186 | Last updated: 2017-10-10 |
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187 | |
188 | Documentation of the uvesafb options is loosely based on vesafb.txt. |