Rajveer Singh said on Sun, Dec 26, 2010 at 09:58:29AM +0530,: > By going through the above points, I understood that kernel uses > the drivers which gives features like udma, pagged r/w, caching > etc. whereas the bios way to access the disk is restricted to > specific track and sectors. So if we don't require these features > like udma, pagged r/w, caching etc. and only needed the restricted > access to specific track and sectors then kernel may detect the new > disk(SATA/ATA/SCSI/SAS etc) the same way as the bios without > specific drivers. Correct me if I'm wrong.
Well, I again say, there is no such thing as the kernel accessing a disk. The kernel accesses the chipset, which in turn accesses the disk. That is more accurate way of putting it. If the kernel does not support the disk controller chipset, there is no way the disk can be accessed. I doubt that the kernel can do anything like the restricted access the BIOS does. There are lot of holes in how I understand things, but I guess while the BIOS uses some feature / "minimal set of requirements for bootup" to access the hard disk, the kernel access the controller chipset, which in turns control the disk. Here is a small "homework" for you. Issue this command, preferably as non-root user. lspci -v -v |grep -i ide "lspci" lists the various PCI devices on the MoBo. -v -v makes it extra verbose; and the output is filtered case insensitively (grep -i), searching for the letters ide. The output I get here is 00:06.0 IDE interface: nVidia Corporation MCP61 IDE (rev a2) (prog-if 8a [Master SecP PriP]) 00:08.0 IDE interface: nVidia Corporation MCP61 SATA Controller (rev a2) (prog-if 85 [Master SecO PriO]) 00:08.1 IDE interface: nVidia Corporation MCP61 SATA Controller (rev a2) (prog-if 85 [Master SecO PriO]) You will of course, get different output. This tells me that the Mo-Bo has a disk controller from nVidia Corporation, and the chipset model is MCP61. There is no way my kernel can access the Samsung/ WD / LG / Seagate disks connected to this MoBo unless the kernel supports the nvidia MCP 61 controller.(of course, it is supported here). If the chipset was not supported, no way I can access the same disks. It is rare to find disk controller chipsets not supported by the kernel; the problem usually occurs with the graphic controllers. But as I said, I have had trouble with IDE controller chipsets. YMMV. Problems, if any, is usually with RAID controllers, rarely with IDE / SATA. If you have problems with IDE / SATA, chances could be that it is because the module was not built / loaded / included in the initramfs. When you encounter such problems, you may be better off talking to the list / forum / IRC channel of the respective distribution. You can repeat the lspci command above as super user with "grep -i -C3" to get a 3 line context. You need to be suepr user, else you will find "access denied" errors. Will show you the kernel modules in use. And again, I am no kernel / HW guru. I have not installed on systems which I have not used, which is probably less than the number of years I have been using GNU/Linux. -- Mahesh T. Pai || http://[paivakil|fizzard].blogspot.com _______________________________________________ Ilugd mailing list Ilugd@lists.linux-delhi.org http://frodo.hserus.net/mailman/listinfo/ilugd
