[PATCH] fix warning in pci_slot

[PATCH] fix warning in pci_slot

[Matthew Wilcox]

I get warnings about 'device' possibly being used uninitialised.  While I
can deduce this is not true, it seems that GCC can't.  This patch changes
`check_slot' to return device on success and -1 on error, which shuts
GCC up.

Signed-off-by: Matthew Wilcox <willy@linux.intel.com>

I couldn't say I've tested this in any meaningful way.

diff --git a/drivers/acpi/pci_slot.c b/drivers/acpi/pci_slot.c
index b9ab030..61bac61 100644
--- a/drivers/acpi/pci_slot.c
+++ b/drivers/acpi/pci_slot.c
@@ -76,9 +76,9 @@ static struct acpi_pci_driver acpi_pci_slot_driver = {
 };
 
 static int
-check_slot(acpi_handle handle, int *device, unsigned long *sun)
+check_slot(acpi_handle handle, unsigned long *sun)
 {
-	int retval = 0;
+	int device = -1;
 	unsigned long adr, sta;
 	acpi_status status;
 	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
@@ -89,32 +89,27 @@ check_slot(acpi_handle handle, int *device, unsigned long *sun)
 	if (check_sta_before_sun) {
 		/* If SxFy doesn't have _STA, we just assume it's there */
 		status = acpi_evaluate_integer(handle, "_STA", NULL, &sta);
-		if (ACPI_SUCCESS(status) && !(sta & ACPI_STA_DEVICE_PRESENT)) {
-			retval = -1;
+		if (ACPI_SUCCESS(status) && !(sta & ACPI_STA_DEVICE_PRESENT))
 			goto out;
-		}
 	}
 
 	status = acpi_evaluate_integer(handle, "_ADR", NULL, &adr);
 	if (ACPI_FAILURE(status)) {
 		dbg("_ADR returned %d on %s\n", status, (char *)buffer.pointer);
-		retval = -1;
 		goto out;
 	}
 
-	*device = (adr >> 16) & 0xffff;
-
 	/* No _SUN == not a slot == bail */
 	status = acpi_evaluate_integer(handle, "_SUN", NULL, sun);
 	if (ACPI_FAILURE(status)) {
 		dbg("_SUN returned %d on %s\n", status, (char *)buffer.pointer);
-		retval = -1;
 		goto out;
 	}
 
+	device = (adr >> 16) & 0xffff;
 out:
 	kfree(buffer.pointer);
-	return retval;
+	return device;
 }
 
 struct callback_args {
@@ -144,7 +139,8 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
 	struct callback_args *parent_context = context;
 	struct pci_bus *pci_bus = parent_context->pci_bus;
 
-	if (check_slot(handle, &device, &sun))
+	device = check_slot(handle, &sun);
+	if (device < 0)
 		return AE_OK;
 
 	slot = kmalloc(sizeof(*slot), GFP_KERNEL);

-- 
Intel are signing my paycheques ... these opinions are still mine
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."

Re: [PATCH] fix warning in pci_slot

[Alex Chiang]

* Matthew Wilcox <matthew@wil.cx>:
> 
> I get warnings about 'device' possibly being used uninitialised.  While I
> can deduce this is not true, it seems that GCC can't.  This patch changes
> `check_slot' to return device on success and -1 on error, which shuts
> GCC up.
> 
> Signed-off-by: Matthew Wilcox <willy@linux.intel.com>

Perhaps a more meaningful patch title, like:

	fix bogus "'device' may be used uninitialized" warning in pci_slot

But otherwise,

Acked-by: Alex Chiang <achiang@hp.com>

Thanks.

/ac

> 
> I couldn't say I've tested this in any meaningful way.
> 
> diff --git a/drivers/acpi/pci_slot.c b/drivers/acpi/pci_slot.c
> index b9ab030..61bac61 100644
> --- a/drivers/acpi/pci_slot.c
> +++ b/drivers/acpi/pci_slot.c
> @@ -76,9 +76,9 @@ static struct acpi_pci_driver acpi_pci_slot_driver = {
>  };
>  
>  static int
> -check_slot(acpi_handle handle, int *device, unsigned long *sun)
> +check_slot(acpi_handle handle, unsigned long *sun)
>  {
> -	int retval = 0;
> +	int device = -1;
>  	unsigned long adr, sta;
>  	acpi_status status;
>  	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> @@ -89,32 +89,27 @@ check_slot(acpi_handle handle, int *device, unsigned long *sun)
>  	if (check_sta_before_sun) {
>  		/* If SxFy doesn't have _STA, we just assume it's there */
>  		status = acpi_evaluate_integer(handle, "_STA", NULL, &sta);
> -		if (ACPI_SUCCESS(status) && !(sta & ACPI_STA_DEVICE_PRESENT)) {
> -			retval = -1;
> +		if (ACPI_SUCCESS(status) && !(sta & ACPI_STA_DEVICE_PRESENT))
>  			goto out;
> -		}
>  	}
>  
>  	status = acpi_evaluate_integer(handle, "_ADR", NULL, &adr);
>  	if (ACPI_FAILURE(status)) {
>  		dbg("_ADR returned %d on %s\n", status, (char *)buffer.pointer);
> -		retval = -1;
>  		goto out;
>  	}
>  
> -	*device = (adr >> 16) & 0xffff;
> -
>  	/* No _SUN == not a slot == bail */
>  	status = acpi_evaluate_integer(handle, "_SUN", NULL, sun);
>  	if (ACPI_FAILURE(status)) {
>  		dbg("_SUN returned %d on %s\n", status, (char *)buffer.pointer);
> -		retval = -1;
>  		goto out;
>  	}
>  
> +	device = (adr >> 16) & 0xffff;
>  out:
>  	kfree(buffer.pointer);
> -	return retval;
> +	return device;
>  }
>  
>  struct callback_args {
> @@ -144,7 +139,8 @@ register_slot(acpi_handle handle, u32 lvl, void *context, void **rv)
>  	struct callback_args *parent_context = context;
>  	struct pci_bus *pci_bus = parent_context->pci_bus;
>  
> -	if (check_slot(handle, &device, &sun))
> +	device = check_slot(handle, &sun);
> +	if (device < 0)
>  		return AE_OK;
>  
>  	slot = kmalloc(sizeof(*slot), GFP_KERNEL);
> 
> -- 
> Intel are signing my paycheques ... these opinions are still mine
> "Bill, look, we understand that you're interested in selling us this
> operating system, but compare it to ours.  We can't possibly take such
> a retrograde step."
> 

Re: [PATCH] fix warning in pci_slot

[Jesse Barnes]

On Tuesday, July 22, 2008 1:56 pm Alex Chiang wrote:
> * Matthew Wilcox <matthew@wil.cx>:
> > I get warnings about 'device' possibly being used uninitialised.  While I
> > can deduce this is not true, it seems that GCC can't.  This patch changes
> > `check_slot' to return device on success and -1 on error, which shuts
> > GCC up.
> >
> > Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
>
> Perhaps a more meaningful patch title, like:
>
> 	fix bogus "'device' may be used uninitialized" warning in pci_slot
>
> But otherwise,
>
> Acked-by: Alex Chiang <achiang@hp.com>

Applied, thanks.

Jesse