serial: define FIXED_PORT flag for serial_core

At present, the serial core always allows setserial in userspace to change the
port address, irq and base clock of any serial port.  That makes sense for
legacy ISA ports, but not for (say) embedded ns16550 compatible serial ports
at peculiar addresses.  In these cases, the kernel code configuring the ports
must know exactly where they are, and their clocking arrangements (which can
be unusual on embedded boards).  It doesn't make sense for userspace to change
these settings.

Therefore, this patch defines a UPF_FIXED_PORT flag for the uart_port
structure.  If this flag is set when the serial port is configured, any
attempts to alter the port's type, io address, irq or base clock with
setserial are ignored.

In addition this patch uses the new flag for on-chip serial ports probed in
arch/powerpc/kernel/legacy_serial.c, and for other hard-wired serial ports
probed by drivers/serial/of_serial.c.

Signed-off-by: David Gibson <dwg@au1.ibm.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/powerpc/kernel/legacy_serial.c b/arch/powerpc/kernel/legacy_serial.c
index 63dd2c3ad95e0c200716404aba1e0b0045c2eb97..ae4836ea7442711f0f36c80e2ab90e6ae42fbedb 100644 (file)
--- a/arch/powerpc/kernel/legacy_serial.c
+++ b/arch/powerpc/kernel/legacy_serial.c
@@ -115,7 +115,8 @@ static int __init add_legacy_soc_port(struct device_node *np,
 {
        u64 addr;
        const u32 *addrp;
-       upf_t flags = UPF_BOOT_AUTOCONF | UPF_SKIP_TEST | UPF_SHARE_IRQ;
+       upf_t flags = UPF_BOOT_AUTOCONF | UPF_SKIP_TEST | UPF_SHARE_IRQ
+               | UPF_FIXED_PORT;
        struct device_node *tsi = of_get_parent(np);
 
        /* We only support ports that have a clock frequency properly

diff --git a/drivers/serial/of_serial.c b/drivers/serial/of_serial.c
index 09b0b736a751e6e4bbe9ff5537b1a143b6cbd06a..336d0f4580d9484f08955952efbb757e2d877769 100644 (file)
--- a/drivers/serial/of_serial.c
+++ b/drivers/serial/of_serial.c
@@ -48,7 +48,8 @@ static int __devinit of_platform_serial_setup(struct of_device *ofdev,
        port->iotype = UPIO_MEM;
        port->type = type;
        port->uartclk = *clk;
-       port->flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP;
+       port->flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP
+               | UPF_FIXED_PORT;
        port->dev = &ofdev->dev;
        port->custom_divisor = *clk / (16 * (*spd));
 

diff --git a/drivers/serial/serial_core.c b/drivers/serial/serial_core.c
index a677133ab2d4fbf0d0625cb29bd6e86f328eda47..f409be37b62f43e1970e01ab401734793cc3dd60 100644 (file)
--- a/drivers/serial/serial_core.c
+++ b/drivers/serial/serial_core.c
@@ -672,19 +672,21 @@ static int uart_set_info(struct uart_state *state,
         */
        mutex_lock(&state->mutex);
 
-       change_irq  = new_serial.irq != port->irq;
+       change_irq  = !(port->flags & UPF_FIXED_PORT)
+               && new_serial.irq != port->irq;
 
        /*
         * Since changing the 'type' of the port changes its resource
         * allocations, we should treat type changes the same as
         * IO port changes.
         */
-       change_port = new_port != port->iobase ||
-                     (unsigned long)new_serial.iomem_base != port->mapbase ||
-                     new_serial.hub6 != port->hub6 ||
-                     new_serial.io_type != port->iotype ||
-                     new_serial.iomem_reg_shift != port->regshift ||
-                     new_serial.type != port->type;
+       change_port = !(port->flags & UPF_FIXED_PORT)
+               && (new_port != port->iobase ||
+                   (unsigned long)new_serial.iomem_base != port->mapbase ||
+                   new_serial.hub6 != port->hub6 ||
+                   new_serial.io_type != port->iotype ||
+                   new_serial.iomem_reg_shift != port->regshift ||
+                   new_serial.type != port->type);
 
        old_flags = port->flags;
        new_flags = new_serial.flags;
@@ -796,8 +798,10 @@ static int uart_set_info(struct uart_state *state,
                }
        }
 
-       port->irq              = new_serial.irq;
-       port->uartclk          = new_serial.baud_base * 16;
+       if (change_irq)
+               port->irq      = new_serial.irq;
+       if (!(port->flags & UPF_FIXED_PORT))
+               port->uartclk  = new_serial.baud_base * 16;
        port->flags            = (port->flags & ~UPF_CHANGE_MASK) |
                                 (new_flags & UPF_CHANGE_MASK);
        port->custom_divisor   = new_serial.custom_divisor;

diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index d242c731491f2430288f0a936d4febf41157c9cb..aadbfd30763fddef836e4a021b9b5bbb719c82b3 100644 (file)
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -263,6 +263,7 @@ struct uart_port {
 #define UPF_CONS_FLOW          ((__force upf_t) (1 << 23))
 #define UPF_SHARE_IRQ          ((__force upf_t) (1 << 24))
 #define UPF_BOOT_AUTOCONF      ((__force upf_t) (1 << 28))
+#define UPF_FIXED_PORT         ((__force upf_t) (1 << 29))
 #define UPF_DEAD               ((__force upf_t) (1 << 30))
 #define UPF_IOREMAP            ((__force upf_t) (1 << 31))