vfio-mdev: turn VFIO_MDEV into a selectable symbol

VFIO_MDEV is just a library with helpers for the drivers.  Stop making
it a user choice and just select it by the drivers that use the helpers.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
Link: https://lore.kernel.org/r/20230110091009.474427-3-hch@lst.deSigned-off-by: Alex Williamson <alex.williamson@redhat.com>

Documentation/s390/vfio-ap.rst

@@ -553,7 +553,6 @@ These are the steps:
    * ZCRYPT
    * S390_AP_IOMMU
    * VFIO
-   * VFIO_MDEV
    * KVM
 
    If using make menuconfig select the following to build the vfio_ap module::

arch/s390/Kconfig

@@ -713,7 +713,8 @@ config EADM_SCH
 config VFIO_CCW
 	def_tristate n
 	prompt "Support for VFIO-CCW subchannels"
-	depends on S390_CCW_IOMMU && VFIO_MDEV
+	depends on S390_CCW_IOMMU
+	select VFIO_MDEV
 	help
 	  This driver allows usage of I/O subchannels via VFIO-CCW.
 
@@ -723,7 +724,8 @@ config VFIO_CCW
 config VFIO_AP
 	def_tristate n
 	prompt "VFIO support for AP devices"
-	depends on S390_AP_IOMMU && VFIO_MDEV && KVM
+	depends on S390_AP_IOMMU && KVM
+	select VFIO_MDEV
 	depends on ZCRYPT
 	help
 	  This driver grants access to Adjunct Processor (AP) devices

arch/s390/configs/debug_defconfig

@@ -594,7 +594,6 @@ CONFIG_SYNC_FILE=y
 CONFIG_VFIO=m
 CONFIG_VFIO_PCI=m
 CONFIG_MLX5_VFIO_PCI=m
-CONFIG_VFIO_MDEV=m
 CONFIG_VIRTIO_PCI=m
 CONFIG_VIRTIO_BALLOON=m
 CONFIG_VIRTIO_INPUT=y

arch/s390/configs/defconfig

@@ -583,7 +583,6 @@ CONFIG_SYNC_FILE=y
 CONFIG_VFIO=m
 CONFIG_VFIO_PCI=m
 CONFIG_MLX5_VFIO_PCI=m
-CONFIG_VFIO_MDEV=m
 CONFIG_VIRTIO_PCI=m
 CONFIG_VIRTIO_BALLOON=m
 CONFIG_VIRTIO_INPUT=y

drivers/gpu/drm/i915/Kconfig

@@ -116,9 +116,9 @@ config DRM_I915_GVT_KVMGT
 	depends on X86
 	depends on 64BIT
 	depends on KVM
-	depends on VFIO_MDEV
 	select DRM_I915_GVT
 	select KVM_EXTERNAL_WRITE_TRACKING
+	select VFIO_MDEV
 
 	help
 	  Choose this option if you want to enable Intel GVT-g graphics

drivers/vfio/mdev/Kconfig

 # SPDX-License-Identifier: GPL-2.0-only
 
 config VFIO_MDEV
-	tristate "Mediated device driver framework"
-	default n
-	help
-	  Provides a framework to virtualize devices.
-	  See Documentation/driver-api/vfio-mediated-device.rst for more details.
-
-	  If you don't know what do here, say N.
+	tristate

samples/Kconfig

@@ -185,14 +185,14 @@ config SAMPLE_UHID
 
 config SAMPLE_VFIO_MDEV_MTTY
 	tristate "Build VFIO mtty example mediated device sample code"
-	depends on VFIO_MDEV
+	select VFIO_MDEV
 	help
 	  Build a virtual tty sample driver for use as a VFIO
 	  mediated device
 
 config SAMPLE_VFIO_MDEV_MDPY
 	tristate "Build VFIO mdpy example mediated device sample code"
-	depends on VFIO_MDEV
+	select VFIO_MDEV
 	help
 	  Build a virtual display sample driver for use as a VFIO
 	  mediated device.  It is a simple framebuffer and supports
@@ -209,7 +209,7 @@ config SAMPLE_VFIO_MDEV_MDPY_FB
 
 config SAMPLE_VFIO_MDEV_MBOCHS
 	tristate "Build VFIO mdpy example mediated device sample code"
-	depends on VFIO_MDEV
+	select VFIO_MDEV
 	select DMA_SHARED_BUFFER
 	help
 	  Build a virtual display sample driver for use as a VFIO