Hello! loody schrieb: > As far as I know, the cpu will set the PC to irq/fiq vector when the > these exceptions are triggered. And these pointers are usually at the > beginning position of bootloader, if bootloader wants to pass these > functions to kernel, there may be some instructions like "b xxxxxx'. > > If uboot don't handle these exceptions, how the kernel knows these events?
Probably you are confusing a bootloader with something like a BIOS. When a Linux kernel starts it just copies some data (like information contained in ATAGS on ARM processors) and activates the MMU. U-Boot just works when the MMU is disabled because it uses physical addresses. Usually the interrupt handler code isn't used by *plain* U-Boot, and on many platforms it may be totally out-dated. The big advantage of this concept is that you can implement your own interrupt handler without fearing conflicts with other interrupt handler stuff, so the runtime behaviour of such a single interrupt handler can be much more predictable than in complex environments like Linux. And the answer to the next question which you probably have in mind is: No, the U-Boot process scheduler or realtime kernel also doesn't use interrupts because the is no kernel. Everything is based on a main loop. Yes, on implication is that U-Boot also won't respond to ARP/ICMP ECHO or similar network requests when it isn't running a network command like bootp, dhcp or ftp. And also timer handling is not interrupt driven but instead performed by polling some hardware timer registers. Regards Andreas Schweigstill -- Dipl.-Phys. Andreas Schweigstill Schweigstill IT | Embedded Systems Schauenburgerstraße 116, D-24118 Kiel, Germany Phone: (+49) 431 5606-435, Fax: (+49) 431 5606-436 Mobile: (+49) 171 6921973, Web: http://www.schweigstill.de/ ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ U-Boot-Users mailing list U-Boot-Users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/u-boot-users
