MicroSemi Switchtec management interface driver

Microsemi's "Switchtec" line of PCI switch devices is already well
supported by the kernel with standard PCI switch drivers.  However, the
Switchtec device advertises a special management endpoint with a separate
PCI function address and class code.  This endpoint enables some additional
functionality which includes:

 * Packet and Byte Counters
 * Switch Firmware Upgrades
 * Event and Error logs
 * Querying port link status
 * Custom user firmware commands

Add a switchtec kernel module which provides PCI driver that exposes a char
device.  The char device provides userspace access to this interface
through read, write and (optionally) poll calls.

A userspace tool and library which utilizes this interface is available
at [1].  This tool takes inspiration (and borrows some code) from
nvme-cli [2].  The tool is largely complete at this time but additional
features may be added in the future.

[1] https://github.com/sbates130272/switchtec-user
[2] https://github.com/linux-nvme/nvme-cli

[Dan Carpenter <dan.carpenter@oracle.com>: don't invert error codes]
[Christophe JAILLET <christophe.jaillet@wanadoo.fr>: fix
switchtec_dev_open() error handling]
Tested-by: Krishna Dhulipala <krishnad@fb.com>
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Stephen Bates <stephen.bates@microsemi.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Wei Zhang <wzhang@fb.com>
Reviewed-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

MAINTAINERS

@@ -9655,6 +9655,14 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/pci/aardvark-pci.txt
 F:	drivers/pci/host/pci-aardvark.c
 
+PCI DRIVER FOR MICROSEMI SWITCHTEC
+M:	Kurt Schwemmer <kurt.schwemmer@microsemi.com>
+M:	Stephen Bates <stephen.bates@microsemi.com>
+M:	Logan Gunthorpe <logang@deltatee.com>
+L:	linux-pci@vger.kernel.org
+S:	Maintained
+F:	drivers/pci/switch/switchtec*
+
 PCI DRIVER FOR NVIDIA TEGRA
 M:	Thierry Reding <thierry.reding@gmail.com>
 L:	linux-tegra@vger.kernel.org

drivers/pci/Kconfig

@@ -134,3 +134,4 @@ config PCI_HYPERV
 source "drivers/pci/hotplug/Kconfig"
 source "drivers/pci/dwc/Kconfig"
 source "drivers/pci/host/Kconfig"
+source "drivers/pci/switch/Kconfig"

drivers/pci/Makefile

@@ -68,3 +68,4 @@ ccflags-$(CONFIG_PCI_DEBUG) := -DDEBUG
 
 # PCI host controller drivers
 obj-y += host/
+obj-y += switch/

drivers/pci/switch/Kconfig

@@ -0,0 +1,13 @@
+menu "PCI switch controller drivers"
+	depends on PCI
+
+config PCI_SW_SWITCHTEC
+	tristate "MicroSemi Switchtec PCIe Switch Management Driver"
+	help
+	 Enables support for the management interface for the MicroSemi
+	 Switchtec series of PCIe switches. Supports userspace access
+	 to submit MRPC commands to the switch via /dev/switchtecX
+	 devices. See <file:Documentation/switchtec.txt> for more
+	 information.
+
+endmenu

drivers/pci/switch/Makefile

@@ -0,0 +1 @@
+obj-$(CONFIG_PCI_SW_SWITCHTEC) += switchtec.o