1 00:00:00,005 --> 00:00:02,001 - [Instructor] So we've already mentioned 2 00:00:02,001 --> 00:00:08,009 that your config options are stored in the .config file, 3 00:00:08,009 --> 00:00:11,000 and you overwrite that 4 00:00:11,000 --> 00:00:14,001 whenever you make a change with make menuconfig 5 00:00:14,001 --> 00:00:17,005 or make xconfig and save it. 6 00:00:17,005 --> 00:00:20,004 So all your choices are in that one text file. 7 00:00:20,004 --> 00:00:22,002 So you can make a copy of that, 8 00:00:22,002 --> 00:00:26,004 or someone could give you one to start with. 9 00:00:26,004 --> 00:00:28,008 So you could overwrite .config with a copy of something, 10 00:00:28,008 --> 00:00:30,008 then do make menuconfig, 11 00:00:30,008 --> 00:00:33,006 and it would start with that. 12 00:00:33,006 --> 00:00:35,001 And if the one you got 13 00:00:35,001 --> 00:00:38,008 doesn't match your current kernel version, 14 00:00:38,008 --> 00:00:43,007 then make menuconfig typically will kind of touch it up 15 00:00:43,007 --> 00:00:45,007 to include everything 16 00:00:45,007 --> 00:00:48,002 because it's going to go through all the Kconfigs 17 00:00:48,002 --> 00:00:51,006 all through the tree and find all the choices. 18 00:00:51,006 --> 00:00:54,005 And if there's stuff not in your .config, 19 00:00:54,005 --> 00:00:59,003 then it will save out the defaults for you. 20 00:00:59,003 --> 00:01:03,007 Your distribution, like Ubuntu, may give you a config file. 21 00:01:03,007 --> 00:01:05,009 It might be in /boot. 22 00:01:05,009 --> 00:01:08,002 It's also possible that in /proc, 23 00:01:08,002 --> 00:01:12,000 there might be a compressed version of your config file 24 00:01:12,000 --> 00:01:13,007 for the kernel if the kernel was built 25 00:01:13,007 --> 00:01:16,002 with that particular option. 26 00:01:16,002 --> 00:01:19,000 So if your distro gives you one, 27 00:01:19,000 --> 00:01:21,001 then you probably want to start with that one. 28 00:01:21,001 --> 00:01:23,007 Now, you might need to tweak it a little bit. 29 00:01:23,007 --> 00:01:26,000 For example, for the Ubuntu one, 30 00:01:26,000 --> 00:01:29,005 it comes with some trust key paths in it 31 00:01:29,005 --> 00:01:31,004 that probably aren't right. 32 00:01:31,004 --> 00:01:35,005 So you might need to disable some of the keys 33 00:01:35,005 --> 00:01:40,004 or set the config variable system trusted keys 34 00:01:40,004 --> 00:01:41,008 to be blank. 35 00:01:41,008 --> 00:01:44,001 So you could do that with make menuconfig, 36 00:01:44,001 --> 00:01:48,003 or it turns out, from the kernel top level directory, 37 00:01:48,003 --> 00:01:51,001 there's a subdirectory called scripts 38 00:01:51,001 --> 00:01:53,006 and there's a script called config. 39 00:01:53,006 --> 00:01:54,009 And just on the command line, 40 00:01:54,009 --> 00:01:58,001 you can set some config options if you want. 41 00:01:58,001 --> 00:01:59,005 For the kernel source, 42 00:01:59,005 --> 00:02:02,000 it's also common that 43 00:02:02,000 --> 00:02:08,002 there's a whole bunch of predefined config files available. 44 00:02:08,002 --> 00:02:13,008 And there will be some for x86, x86-64, 45 00:02:13,008 --> 00:02:16,001 but typically, there's lots of them 46 00:02:16,001 --> 00:02:20,004 from other architectures, like maybe for ARM. 47 00:02:20,004 --> 00:02:22,001 So underneath the arch 48 00:02:22,001 --> 00:02:25,002 in a particular architecture directory, 49 00:02:25,002 --> 00:02:27,008 look for another subdirectory called configs, 50 00:02:27,008 --> 00:02:29,004 and you can look in there 51 00:02:29,004 --> 00:02:31,008 and see if there's a bunch of config files. 52 00:02:31,008 --> 00:02:36,002 Maybe there's one for the imx_v4_v5. 53 00:02:36,002 --> 00:02:42,002 And these config files have a suffix of _defconfig. 54 00:02:42,002 --> 00:02:45,003 And so you can do a make with that. 55 00:02:45,003 --> 00:02:47,004 And usually for different architecture, 56 00:02:47,004 --> 00:02:49,008 you would say make ARCH= 57 00:02:49,008 --> 00:02:51,007 and then the architecture space, 58 00:02:51,007 --> 00:02:53,006 then the name of the _defconfig. 59 00:02:53,006 --> 00:02:55,005 And the word ARCH is all in capital letters. 60 00:02:55,005 --> 00:02:58,005 So make space ARCH, all in capital letters, 61 00:02:58,005 --> 00:03:00,007 =arm, in lowercase, 62 00:03:00,007 --> 00:03:05,003 name of the directory underarch name of the _defconfig file. 63 00:03:05,003 --> 00:03:07,000 And then it will read that in, 64 00:03:07,000 --> 00:03:10,009 and it'll create the .config from that. 65 00:03:10,009 --> 00:03:12,001 And so like I said, 66 00:03:12,001 --> 00:03:14,009 you can potentially configure your kernel 67 00:03:14,009 --> 00:03:17,006 to save its config file. 68 00:03:17,006 --> 00:03:20,004 So underneath General Setup 69 00:03:20,004 --> 00:03:24,001 is a box for Kernel .config support. 70 00:03:24,001 --> 00:03:26,009 And then it will allow you to choose 71 00:03:26,009 --> 00:03:28,009 to make the .config available 72 00:03:28,009 --> 00:03:34,000 through a file in /proc called config.gz. 73 00:03:34,000 --> 00:03:36,006 I've often found that's not turned on, 74 00:03:36,006 --> 00:03:40,003 but it could be handy if it is. 75 00:03:40,003 --> 00:03:42,002 All throughout the kernel source tree 76 00:03:42,002 --> 00:03:44,003 are these files called Kconfig 77 00:03:44,003 --> 00:03:47,009 or Kconfig with some suffixes. 78 00:03:47,009 --> 00:03:50,001 And this is where all the information 79 00:03:50,001 --> 00:03:52,008 for menuconfig or xconfig is stored. 80 00:03:52,008 --> 00:03:54,007 So those are text files. 81 00:03:54,007 --> 00:03:55,005 You can read 'em, 82 00:03:55,005 --> 00:03:57,003 and you can find out the names of variables. 83 00:03:57,003 --> 00:04:01,000 You can see if they're tristate, 84 00:04:01,000 --> 00:04:04,001 meaning it could be a module or static or nothing, 85 00:04:04,001 --> 00:04:05,007 or whether it's Boolean, 86 00:04:05,007 --> 00:04:08,009 meaning either you get it or you don't, 87 00:04:08,009 --> 00:04:10,000 and the help. 88 00:04:10,000 --> 00:04:11,001 So all that information 89 00:04:11,001 --> 00:04:14,000 that you see in make menuconfig is coming 90 00:04:14,000 --> 00:04:16,002 from these Kconfig files 91 00:04:16,002 --> 00:04:19,000 all distributed throughout the file system.