Fix dev -p command for systems with virtual devices

Hi Dave

Running 'dev -p' command on PowerPC systems with virtual
devices (ie
no real PCI devices) fails with the following message:

dev: invalid kernel virtual address: 98  type: "pci bus
number"

It should instead report that there are no _real_ PCI
devices to list.
The following patch addresses this issue. Currently it just
prints a 
message letting the user know of the absence of pci devices,
but it
might be a good idea to list down the virtual devices
present in the 
system in such cases. I am working on a patch for that too,
probably
will discuss that on another thread.

Please provide your comments/suggestions.

Thanks
Rachita



 On PowerPC machines configured with virtual devices(VIO) it
is possible
 that there are no _real_ PCI devices. Hence it is
reasonable that 'dev -p' 
 would not list anything. This patch identifies such cases
and displays a
 message appropriately.

Signed-off-by: Rachita Kothiyal <rachitain.ibm.com>
---

 dev.c |   30 +++++++++++++++++++++++++++---
 1 files changed, 27 insertions(+), 3 deletions(-)

diff -puN dev.c~fix-vio-pci-device dev.c
--- crash-4.0-3.9/dev.c~fix-vio-pci-device	2006-12-22
13:32:02.737262096 +0530
+++ crash-4.0-3.9-rachita/dev.c	2006-12-22
13:48:44.984897296 +0530
 -1955,13
+1955,11  do_pci(void)
 	unsigned int      class;
 	unsigned short    device, vendor;
 	unsigned char     busno;
-	ulong             *devlist, bus, devfn, tmp;
+	ulong             *devlist, bus, devfn, tmp, prev, next;
 	char 		  buf1[BUFSIZE];
 	char 		  buf2[BUFSIZE];
 	char 		  buf3[BUFSIZE];
 
-	fprintf(fp, "%s BU:SL.FN CLASS:
VENDOR-DEVICEn",
-		mkstring(buf1, VADDR_PRLEN, CENTER|LJUST,
"PCI_DEV"));
 
 	BZERO(&pcilist_data, sizeof(struct list_data));
 
 -1972,11
+1970,34  do_pci(void)
                         FAULT_ON_ERROR);
                 pcilist_data.end =
symbol_value("pci_devices");
                 pcilist_data.list_head_offset =
OFFSET(pci_dev_global_list);
+		readmem(symbol_value("pci_devices") +
OFFSET(list_head_prev),
+			KVADDR, &prev, sizeof(void *), "list head
prev",
+			FAULT_ON_ERROR);
+                /*
+		 * Check if this system does not have any PCI devices.
+		 * Possible on PowerPC machines with VIO configured.
+		 */
+		if ((pcilist_data.start == pcilist_data.end) &&
+ 		   (prev == pcilist_data.end)) {
+			fprintf(fp, "No PCI devices found on this
system.n");
+			return;
+		}
 
 	} else {
 		get_symbol_data("pci_devices", sizeof(void *),
 				&pcilist_data.start);
 		pcilist_data.member_offset = OFFSET(pci_dev_next);
+                /*
+		 * Check if this system does not have any PCI devices.
+		 * Possible on PowerPC machines with VIO configured.
+		 */
+		readmem(pcilist_data.start + pcilist_data.member_offset,
+			KVADDR, &next, sizeof(void *), "pci dev
next",
+			FAULT_ON_ERROR);
+		if (!next) {
+			fprintf(fp, "No PCI devices found on this
system.n");
+			return;
+		}
 	} 
 
 	hq_open();
 -1985,6
+2006,9  do_pci(void)
 	devcnt = retrieve_list(devlist, devcnt);
 	hq_close();
 
+	fprintf(fp, "%s BU:SL.FN CLASS:
VENDOR-DEVICEn",
+		mkstring(buf1, VADDR_PRLEN, CENTER|LJUST,
"PCI_DEV"));
+
 	for (i = 0; i < devcnt; i++) {
 
 		/*
_

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