Building arch/x86/lguest/boot.o triggers two warnings:
arch/x86/lguest/boot.c: In function 'early_put_chars':
arch/x86/lguest/boot.c:1300:5: warning: 'device_len' may be used uninitialized in this function [-Wmaybe-uninitialized]
if (device_len < (offsetof(struct virtio_console_config, emerg_wr)
^
arch/x86/lguest/boot.c:1238:6: note: 'device_len' was declared here
u32 device_len;
^
arch/x86/lguest/boot.c:1306:21: warning: 'device_offset' may be used uninitialized in this function [-Wmaybe-uninitialized]
console_cfg_offset = device_offset;
^
arch/x86/lguest/boot.c:1237:6: note: 'device_offset' was declared here
u32 device_offset;
^
These annoy me for some time now. So I investigated whether
probe_pci_console(), which actually triggers these warnings, could be
reorganized to make these warnings go away. (Because I really dislike to
initialize variables to some default value just to shut up the compiler.)
I came up with this short series. It makes, I think, the code clearer for the
people reading it. And as a bonus the compiler is silent now.
Paul Bolle (2):
lguest: read length of device_cap later
lguest: read offset of device_cap later
arch/x86/lguest/boot.c | 17 +++++------------
1 file changed, 5 insertions(+), 12 deletions(-)
--
2.4.3
Read the offset of the capability with type VIRTIO_PCI_CAP_DEVICE_CFG
only when we're sure we're going to need it. Which is when all checks
have passed and we know we have a virtio console with an emerg_wr field.
Signed-off-by: Paul Bolle <[email protected]>
---
arch/x86/lguest/boot.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 535e3197d0c7..3b0c0eb4abf8 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1233,8 +1233,6 @@ static void write_bar_via_cfg(u32 cfg_offset, u32 off, u32 val)
static void probe_pci_console(void)
{
u8 cap, common_cap = 0, device_cap = 0;
- /* Offset within BAR0 */
- u32 device_offset;
u32 device_len;
/* Avoid recursive printk into here. */
@@ -1258,21 +1256,16 @@ static void probe_pci_console(void)
u8 vndr = read_pci_config_byte(0, 1, 0, cap);
if (vndr == PCI_CAP_ID_VNDR) {
u8 type, bar;
- u32 offset;
type = read_pci_config_byte(0, 1, 0,
cap + offsetof(struct virtio_pci_cap, cfg_type));
bar = read_pci_config_byte(0, 1, 0,
cap + offsetof(struct virtio_pci_cap, bar));
- offset = read_pci_config(0, 1, 0,
- cap + offsetof(struct virtio_pci_cap, offset));
switch (type) {
case VIRTIO_PCI_CAP_DEVICE_CFG:
- if (bar == 0) {
+ if (bar == 0)
device_cap = cap;
- device_offset = offset;
- }
break;
case VIRTIO_PCI_CAP_PCI_CFG:
console_access_cap = cap;
@@ -1302,7 +1295,8 @@ static void probe_pci_console(void)
return;
}
- console_cfg_offset = device_offset;
+ console_cfg_offset = read_pci_config(0, 1, 0,
+ device_cap + offsetof(struct virtio_pci_cap, offset));
printk(KERN_INFO "lguest: Console via virtio-pci emerg_wr\n");
}
--
2.4.3
Read the length of the capability with type VIRTIO_PCI_CAP_DEVICE_CFG
only when we're sure we're going to need it. Which is just before the
check whether the virtio console actually has an emerg_wr field.
Signed-off-by: Paul Bolle <[email protected]>
---
arch/x86/lguest/boot.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 4ba229ac3f4f..535e3197d0c7 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -1258,7 +1258,7 @@ static void probe_pci_console(void)
u8 vndr = read_pci_config_byte(0, 1, 0, cap);
if (vndr == PCI_CAP_ID_VNDR) {
u8 type, bar;
- u32 offset, length;
+ u32 offset;
type = read_pci_config_byte(0, 1, 0,
cap + offsetof(struct virtio_pci_cap, cfg_type));
@@ -1266,15 +1266,12 @@ static void probe_pci_console(void)
cap + offsetof(struct virtio_pci_cap, bar));
offset = read_pci_config(0, 1, 0,
cap + offsetof(struct virtio_pci_cap, offset));
- length = read_pci_config(0, 1, 0,
- cap + offsetof(struct virtio_pci_cap, length));
switch (type) {
case VIRTIO_PCI_CAP_DEVICE_CFG:
if (bar == 0) {
device_cap = cap;
device_offset = offset;
- device_len = length;
}
break;
case VIRTIO_PCI_CAP_PCI_CFG:
@@ -1297,6 +1294,8 @@ static void probe_pci_console(void)
* emerg_wr. If it doesn't support VIRTIO_CONSOLE_F_EMERG_WRITE
* it should ignore the access.
*/
+ device_len = read_pci_config(0, 1, 0,
+ device_cap + offsetof(struct virtio_pci_cap, length));
if (device_len < (offsetof(struct virtio_console_config, emerg_wr)
+ sizeof(u32))) {
printk(KERN_ERR "lguest: console missing emerg_wr field\n");
--
2.4.3