[PATCH 1/3] tty: nozomi: avoid a harmless gcc warning

The nozomi wireless data driver has its own helper function to
transfer data from a FIFO, doing an extra byte swap on big-endian
architectures, presumably to bring the data back into byte-serial
order after readw() or readl() perform their implicit byteswap.

This helper function is used in the receive_data() function to
first read the length into a 32-bit variable, which causes
a compile-time warning:

drivers/tty/nozomi.c: In function 'receive_data':
drivers/tty/nozomi.c:857:9: warning: 'size' may be used uninitialized in this function [-Wmaybe-uninitialized]

The problem is that gcc is unsure whether the data was actually
read or not. We know that it is at this point, so we can replace
it with a single readl() to shut up that warning.

I am leaving the byteswap in there, to preserve the existing
behavior, even though this seems fishy: Reading the length of
the data into a cpu-endian variable should normally not use
a second byteswap on big-endian systems, unless the hardware
is aware of the CPU endianess.

There appears to be a lot more confusion about endianess in this
driver, so it probably has not worked on big-endian systems in
a long time, if ever, and I have no way to test it. It's well
possible that this driver has not been used by anyone in a while,
the last patch that looks like it was tested on the hardware is
from 2008.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/tty/nozomi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/nozomi.c b/drivers/tty/nozomi.c
index 80f9de907563..5cc80b80c82b 100644
--- a/drivers/tty/nozomi.c
+++ b/drivers/tty/nozomi.c

@@ -823,7 +823,7 @@ static int receive_data(enum port_type index, struct nozomi *dc)
 	struct tty_struct *tty = tty_port_tty_get(&port->port);
 	int i, ret;
 
-	read_mem32((u32 *) &size, addr, 4);
+	size = __le32_to_cpu(readl(addr));
 	/*  DBG1( "%d bytes port: %d", size, index); */
 
 	if (tty && test_bit(TTY_THROTTLED, &tty->flags)) {

-- 
2.7.0

When CONFIG_PCI is not set, enabling CONFIG_CYZ_INTR has no
practical effect other than generating a warning about an
unused function:

drivers/tty/cyclades.c:1184:20: warning: 'cyz_interrupt' defined but not used [-Wunused-function]
 static irqreturn_t cyz_interrupt(int irq, void *dev_id)

This adds a dependency to avoid that warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/tty/Kconfig | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig
index c01f45095877..82c4d2e45319 100644
--- a/drivers/tty/Kconfig
+++ b/drivers/tty/Kconfig

@@ -226,7 +226,7 @@ config CYCLADES
 
 config CYZ_INTR
 	bool "Cyclades-Z interrupt mode operation"
-	depends on CYCLADES
+	depends on CYCLADES && PCI
 	help
 	  The Cyclades-Z family of multiport cards allows 2 (two) driver op
 	  modes: polling and interrupt. In polling mode, the driver will check

-- 
2.7.0

xencons_disconnect_backend() is only called from xen_console_remove(),
which is conditionally compiled, so we get a harmless warning when
CONFIG_HVC_XEN_FRONTEND is unset:

hvc/hvc_xen.c:350:12: error: 'xen_console_remove' defined but not used [-Werror=unused-function]

This moves the function down into the same #ifdef section to silence
the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/tty/hvc/hvc_xen.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index fa816b7193b6..11725422dacb 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c

@@ -323,6 +323,7 @@ void xen_console_resume(void)
 	}
 }
 
+#ifdef CONFIG_HVC_XEN_FRONTEND
 static void xencons_disconnect_backend(struct xencons_info *info)
 {
 	if (info->irq > 0)

@@ -363,7 +364,6 @@ static int xen_console_remove(struct xencons_info *info)
 	return 0;
 }
 
-#ifdef CONFIG_HVC_XEN_FRONTEND
 static int xencons_remove(struct xenbus_device *dev)
 {
 	return xen_console_remove(dev_get_drvdata(&dev->dev));

-- 
2.7.0

On 01/25/2016 04:54 PM, Arnd Bergmann wrote:

xencons_disconnect_backend() is only called from xen_console_remove(),

and also from xencons_probe()/xencons_resume(). But those two are also 
under the
same ifdef.

-boris

On Mon, 25 Jan 2016, Boris Ostrovsky wrote:

On 01/25/2016 04:54 PM, Arnd Bergmann wrote:

quoted

xencons_disconnect_backend() is only called from xen_console_remove(),

and also from xencons_probe()/xencons_resume(). But those two are also under
the
same ifdef.

Good point. Aside from this the patch is good.

 

quoted

which is conditionally compiled, so we get a harmless warning when
CONFIG_HVC_XEN_FRONTEND is unset:

hvc/hvc_xen.c:350:12: error: 'xen_console_remove' defined but not used
[-Werror=unused-function]

This moves the function down into the same #ifdef section to silence
the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
  drivers/tty/hvc/hvc_xen.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index fa816b7193b6..11725422dacb 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c

@@ -323,6 +323,7 @@ void xen_console_resume(void)
  	}
  }
  +#ifdef CONFIG_HVC_XEN_FRONTEND
  static void xencons_disconnect_backend(struct xencons_info *info)
  {
  	if (info->irq > 0)

@@ -363,7 +364,6 @@ static int xen_console_remove(struct xencons_info *info)
  	return 0;
  }
  -#ifdef CONFIG_HVC_XEN_FRONTEND
  static int xencons_remove(struct xenbus_device *dev)
  {
  	return xen_console_remove(dev_get_drvdata(&dev->dev));