From: Gerd Hoffmann <kraxel@redhat.com>
Date: Fri, 31 Aug 2007 14:44:10 +0200
Subject: [ide] allow disabling of drivers
Message-id: 46D80D1A.8020305@redhat.com
O-Subject: [RHEL 5.2 patch] bz 247982: need a way to disable ide drivers
Bugzilla: 247982

  Hi,

bug 247982

We want be able to run RHEL-5 fully virtualized guests with
paravirtualized drivers.  Xen emulates a IDE disk controller (PIIX3)
which is driven by the drivers/ide/ subsystem in RHEL-5.

The ide drivers in RHEL-5 are compiled statically, thus it is impossible
to select ide vs. paravirtualied driver by module load order (Fedora 7+
can be handled that way).  That in turn requires an kernel command line
option to disable the ide drivers so the paravirtual driver can step in.

As the paravirtual drivers are optional we can't automatically disable
ide for the xen disk controller, although it can easily be identified by
pci subsystem id.

The patch introduces an "ide=disable" kernel command line option which
disables all drivers in drivers/ide/.

This patch depends on the fix for bug 241338 posted recently.

cheers,
  Gerd

Acked-by: Pete Zaitcev <zaitcev@redhat.com>
Acked-by: "Stephen C. Tweedie" <sct@redhat.com>
Acked-by: Prarit Bhargava <prarit@redhat.com>
---
 drivers/ide/ide.c       |   16 +++++++++++++++-
 drivers/ide/setup-pci.c |    5 +++++
 include/linux/ide.h     |    1 +
 3 files changed, 21 insertions(+), 1 deletions(-)

diff --git a/drivers/ide/ide.c b/drivers/ide/ide.c
index eabd0b2..bbe4ad8 100644
--- a/drivers/ide/ide.c
+++ b/drivers/ide/ide.c
@@ -171,6 +171,7 @@ static const u8 ide_hwif_to_major[] = { IDE0_MAJOR, IDE1_MAJOR,
 static int idebus_parameter;	/* holds the "idebus=" parameter */
 static int system_bus_speed;	/* holds what we think is VESA/PCI bus speed */
 static int initializing;	/* set while initializing built-in drivers */
+int disable_ide;
 
 DECLARE_MUTEX(ide_cfg_sem);
  __cacheline_aligned_in_smp DEFINE_SPINLOCK(ide_lock);
@@ -360,7 +361,14 @@ struct proc_dir_entry *proc_ide_root;
 static struct resource* hwif_request_region(ide_hwif_t *hwif,
 					    unsigned long addr, int num)
 {
-	struct resource *res = request_region(addr, num, hwif->name);
+	struct resource *res;
+
+	if (disable_ide) {
+		printk(KERN_DEBUG "IDE disabled: blocking 0x%lX-0x%lX for %s\n",
+		       addr, addr+num-1, hwif->name);
+		return NULL;
+	}
+	res = request_region(addr, num, hwif->name);
 
 	if (!res)
 		printk(KERN_ERR "%s: I/O resource 0x%lX-0x%lX not free.\n",
@@ -1524,6 +1532,12 @@ static int __init ide_setup(char *s)
 		return 1;
 	}
 
+	if (!strcmp(s, "ide=disable")) {
+		printk(" : disable drivers/ide subsystem\n");
+		disable_ide = 1;
+		return 1;
+	}
+
 #ifdef CONFIG_BLK_DEV_IDEPCI
 	if (!strcmp(s, "ide=reverse")) {
 		ide_scan_direction = 1;
diff --git a/drivers/ide/setup-pci.c b/drivers/ide/setup-pci.c
index eb09452..3ee1314 100644
--- a/drivers/ide/setup-pci.c
+++ b/drivers/ide/setup-pci.c
@@ -785,6 +785,11 @@ static LIST_HEAD(ide_pci_drivers);
 
 int __ide_pci_register_driver(struct pci_driver *driver, struct module *module)
 {
+	if (disable_ide) {
+		printk(KERN_DEBUG "IDE disabled: ignore pci driver %s\n", driver ->name);
+		return -ENODEV;
+	}
+
 	if(!pre_init)
 		return __pci_register_driver(driver, module);
 	driver->driver.owner = module;
diff --git a/include/linux/ide.h b/include/linux/ide.h
index 27fca71..5dd135c 100644
--- a/include/linux/ide.h
+++ b/include/linux/ide.h
@@ -1006,6 +1006,7 @@ int generic_ide_ioctl(ide_drive_t *, struct file *, struct block_device *, unsig
 extern	ide_hwif_t	ide_hwifs[];		/* master data repository */
 #endif
 extern int noautodma;
+extern int disable_ide;
 
 extern int ide_end_request (ide_drive_t *drive, int uptodate, int nrsecs);
 int ide_end_dequeued_request(ide_drive_t *drive, struct request *rq,
-- 
1.5.3.5.645.gbb47