linux-kernel - [PATCH 4/4] config: make USB_MAXBUS configurable and adjust VHCI_NR

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Date:   Tue, 30 Jan 2018 09:36:30 +0100
From:   Salvador Fandino <salva@...del.com>
To:     linux-usb@...r.kernel.org
Cc:     gregkh@...uxfoundation.org, valentina.manea.m@...il.com,
        shuah@...nel.org, linux-kernel@...r.kernel.org,
        Salvador Fandiño <salva@...del.com>
Subject: [PATCH 4/4] config: make USB_MAXBUS configurable and adjust VHCI_NR_HCS top limit

From: Salvador Fandiño <salva@...del.com>

The maximum number of USB host controllers supported by the kernel had
a hard-coded limit of 64. In some scenarios that limit may be not
enough. For instance, in my particular case, I have systems with
thousands of containers running and would like to provide a VHCI
(USBIP host controller) device to every one of them but can't because
of this limit.

This patch adds a new configuration entry for USB_MAXBUS and also
increases the top limit for USBIP_VHCI_NR_HCS (number of VHCI
controllers) accordingly.

Signed-off-by: Salvador Fandiño <salva@...del.com>
---
 drivers/usb/Kconfig       | 9 +++++++++
 drivers/usb/core/hcd.c    | 2 +-
 drivers/usb/usbip/Kconfig | 5 ++++-
 3 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/Kconfig b/drivers/usb/Kconfig
index f699abab1787..78b3e2805d8f 100644
--- a/drivers/usb/Kconfig
+++ b/drivers/usb/Kconfig
@@ -72,6 +72,15 @@ config USB
 	  To compile this driver as a module, choose M here: the
 	  module will be called usbcore.
 
+config USB_MAXBUS
+	int "Maximum number of USB host controllers"
+	range 1 4096
+	default 64
+	---help---
+	  This defines the number of USB host controllers that would be
+	  available, both physical and virtual (for instance, those
+	  used by USB/IP).
+
 config USB_PCI
 	bool "PCI based USB host interface"
 	depends on PCI
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index fc32391a34d5..e1589e950b86 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -83,7 +83,7 @@ DEFINE_IDR (usb_bus_idr);
 EXPORT_SYMBOL_GPL (usb_bus_idr);
 
 /* used when allocating bus numbers */
-#define USB_MAXBUS		64
+#define USB_MAXBUS		CONFIG_USB_MAXBUS
 
 /* used when updating list of hcds */
 DEFINE_MUTEX(usb_bus_idr_lock);	/* exported only for usbfs */
diff --git a/drivers/usb/usbip/Kconfig b/drivers/usb/usbip/Kconfig
index eeefa29f8aa2..cb87bec9dbbb 100644
--- a/drivers/usb/usbip/Kconfig
+++ b/drivers/usb/usbip/Kconfig
@@ -37,7 +37,7 @@ config USBIP_VHCI_HC_PORTS
 
 config USBIP_VHCI_NR_HCS
 	int "Number of USB/IP virtual host controllers"
-	range 1 128
+	range 1 2048
 	default 1
 	depends on USBIP_VHCI_HCD
 	---help---
@@ -46,6 +46,9 @@ config USBIP_VHCI_NR_HCS
 	  virtual host controllers as if adding physical host
 	  controllers.
 
+	  Note that the number of host controllers is also limited by
+	  USB_MAXBUS.
+
 config USBIP_HOST
 	tristate "Host driver"
 	depends on USBIP_CORE && USB
-- 
2.14.1