pciaccess: provide a method to detect if a device is boot VGA

When the linux kernel exposes this information, we can use this interface
in the X server to detect whether the kernel believes the device we
are looking at is the boot VGA device.

Signed-off-by: Dave Airlie <airlied@redhat.com>

4 files changed, 48 insertions, 0 deletions

diff --git a/include/pciaccess.h b/include/pciaccess.h
index cf32876..6413ae0 100644
--- a/include/pciaccess.h
+++ b/include/pciaccess.h
@@ -50,6 +50,8 @@ struct pci_slot_match;
 extern "C" {
 #endif
 
+int pci_device_is_boot_vga(struct pci_device *dev);
+
 int pci_device_read_rom(struct pci_device *dev, void *buffer);
 
 int  __deprecated pci_device_map_region(struct pci_device *dev,
diff --git a/src/common_interface.c b/src/common_interface.c
index 8808fdf..5dcc707 100644
--- a/src/common_interface.c
+++ b/src/common_interface.c
@@ -108,6 +108,20 @@ pci_device_read_rom( struct pci_device * dev, void * buffer )
     return (pci_sys->methods->read_rom)( dev, buffer );
 }
 
+/**
+ * Probe a PCI (VGA) device to determine if its the boot VGA device
+ *
+ * \param dev    Device whose VGA status to query
+ * \return
+ * Zero if not the boot VGA, 1 if the boot VGA.
+ */
+int
+pci_device_is_boot_vga( struct pci_device * dev )
+{
+	if (!pci_sys->methods->boot_vga)
+		return 0;
+	return pci_sys->methods->boot_vga( dev );
+}
 
 /**
  * Probe a PCI device to learn information about the device.
diff --git a/src/linux_sysfs.c b/src/linux_sysfs.c
index 8c3cf67..5afa7d2 100644
--- a/src/linux_sysfs.c
+++ b/src/linux_sysfs.c
@@ -75,6 +75,8 @@ static int pci_device_linux_sysfs_write( struct pci_device * dev,
     const void * data, pciaddr_t offset, pciaddr_t size,
     pciaddr_t * bytes_written );
 
+static int pci_device_linux_sysfs_boot_vga( struct pci_device * dev );
+
 static const struct pci_system_methods linux_sysfs_methods = {
     .destroy = NULL,
     .destroy_device = NULL,
@@ -88,6 +90,7 @@ static const struct pci_system_methods linux_sysfs_methods = {
 
     .fill_capabilities = pci_fill_capabilities_generic,
     .enable = pci_device_linux_sysfs_enable,
+    .boot_vga = pci_device_linux_sysfs_boot_vga,
 };
 
 #define SYS_BUS_PCI "/sys/bus/pci/devices"
@@ -698,3 +701,31 @@ static void pci_device_linux_sysfs_enable(struct pci_device *dev)
     write( fd, "1", 1 );
     close(fd);
 }
+
+static int pci_device_linux_sysfs_boot_vga(struct pci_device *dev)
+{
+    char name[256];
+    char reply[3];
+    int fd, bytes_read;
+    int ret = 0;
+
+    snprintf( name, 255, "%s/%04x:%02x:%02x.%1u/boot_vga",
+	      SYS_BUS_PCI,
+	      dev->domain,
+	      dev->bus,
+	      dev->dev,
+	      dev->func );
+    
+    fd = open( name, O_RDWR );
+    if (fd == -1)
+       return 0;
+
+    bytes_read = read(fd, reply, 1);
+    if (bytes_read != 1)
+	goto out;
+    if (reply[0] == '1')
+	ret = 1;
+out:
+    close(fd);
+    return ret;
+}
diff --git a/src/pciaccess_private.h b/src/pciaccess_private.h
index bff6903..769e181 100644
--- a/src/pciaccess_private.h
+++ b/src/pciaccess_private.h
@@ -60,6 +60,7 @@ struct pci_system_methods {
 
     int (*fill_capabilities)( struct pci_device * dev );
     void (*enable)( struct pci_device *dev );
+    int (*boot_vga)( struct pci_device *dev );
 };
 
 struct pci_device_mapping {