From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <39DAF2C8.6171EABE@serialsystem.com.sg> Date: Wed, 04 Oct 2000 16:05:13 +0700 From: Jari Reply-To: jari.nguyen@smartstors.com MIME-Version: 1.0 To: Scott Anderson CC: jari.nguyen@smartstors.com, linuxppc-embedded@lists.linuxppc.org Subject: Re: mount RAMDISK directly on rom References: <39D485A1.2785C0E4@serialsystem.com.sg> <39DABA39.37B03026@mvista.com> Content-Type: text/plain; charset=us-ascii Sender: owner-linuxppc-embedded@lists.linuxppc.org List-Id: Hello, there is something I need to ask for more information about memory accessing. Scott Anderson wrote: > In general, I would add a driver that exposed your rom as a device and > then just tell your kernel that root is on your device. I think so, but when I modify rd.c, I can not access the memory address on ROM. for example: I can turn on the led of CDK by using the address 0xFF400000. but when I need to read from the address on the ROM, -------------------- 0xFF5C6E11, for example: int b; b = *((char *)0xFF5C6E11); -------------------- I'll see kernel panic like below: -------------------------------------------------------------- NIP: C00AFB8C XER: E000107F LR: C00AFB84 REGS: c0ea1da0 TRAP: 0300 MSR: 00009032 EE: 1 PR: 0 FP: 0 ME: 1 IR/DR: 11 TASK = c0ea0000[16] 'a.out' mm->pgd c0fe1000 Last syscall: 3 last math 00000000 GPR00: 00000000 C0EA1E50 C0EA0000 00000200 00000000 00000000 7FFFFDA4 00000080 GPR08: FF5C6A11 FF5C6E11 C0110000 00000000 30026438 100187EC 100B0490 00000000 GPR16: 100B04F0 90100B0C 00000044 00000000 00009032 00EA1E80 00000000 C000253C GPR24: C000227C 100B04F0 100006CC 00000001 7FFFFBA8 00000200 C0117778 00000200 Call backtrace: 00000284 C0027AA0 C00022D0 30025DC0 0FF094F8 00000000 Kernel panic: kernel access of bad area pc c00afb8c lr c00afb84 address FF5C6E11 tsk a.out/16 -------------------------------------------------------------- Is there anybody tell me what happened? I think that when I working in kernel space, the address is not changed..? and I can access the ROM by using its address, is that right? > I have > successfully used the MTD drivers to do exactly this in the past. I'd > suggest poking around: > http://www.linux-mtd.infradead.org/ > Thanks for your link, I'll try it right away, but I think that I can not use it. ;-( and I must concentrate into creating a driver to manage my task. Is there anything to help me? best regards, Jari ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/