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PCI: endpoint: use ffz() instead of find_first_zero_bit()

PATCH In review Niklas Cassel 2 participants 2 messages Nov 17, 2017 – Nov 21, 2017

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PCI PCI endpoint
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Niklas Cassel

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#0 lore raw

PATCH 1/1 PCI: endpoint: use ffz() instead of find_first_zero_bit()

find_first_zero_bit()'s parameter 'size' is defined in bits, not in bytes.

Calling find_first_zero_bit() with the wrong size unit will lead to insidious bugs.

Fix this by using replacing find_first_zero_bit() with ffz(), since ffz() only works on a single 'unsigned long' and therefore does not need a size argument.

Signed-off-by Niklas Cassel <[email protected]>
---
 drivers/pci/endpoint/pci-ep-cfs.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
drivers/pci/endpoint/pci-ep-cfs.c +1 -2
index 4f74386c1ced..96b984685640 100644
@@ -108,8 +108,7 @@ static int pci_epc_epf_link(struct config_item *epc_item,
 	if (ret)
 		goto err_add_epf;
 
-	func_no = find_first_zero_bit(&epc_group->function_num_map,
-				      sizeof(epc_group->function_num_map));
+	func_no = ffz(epc_group->function_num_map);
 	set_bit(func_no, &epc_group->function_num_map);
 	epf->func_no = func_no;
Signature · 1 line
2.14.2
#1 lore raw

From: Niklas Cassel

Quoted 21 lines

Sent: 17 November 2017 09:43 find_first_zero_bit()'s parameter 'size' is defined in bits, not in bytes.

Calling find_first_zero_bit() with the wrong size unit will lead to insidious bugs.

Fix this by using replacing find_first_zero_bit() with ffz(), since ffz() only works on a single 'unsigned long' and therefore does not need a size argument.

Signed-off-by Niklas Cassel <[email protected]>
---
 drivers/pci/endpoint/pci-ep-cfs.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)
drivers/pci/endpoint/pci-ep-cfs.c +0 -0
index 4f74386c1ced..96b984685640 100644

drivers/pci/endpoint/pci-ep-cfs.c static int pci_epc_epf_link(struct config_item *epc_item, · line 113

Quoted 8 lines
drivers/pci/endpoint/pci-ep-cfs.c +1 -2
@@ -108,8 +108,7 @@ static int pci_epc_epf_link(struct config_item *epc_item,
 	if (ret)
 		goto err_add_epf;
 
-	func_no = find_first_zero_bit(&epc_group->function_num_map,
-				      sizeof(epc_group->function_num_map));
+	func_no = ffz(epc_group->function_num_map);
 	set_bit(func_no, &epc_group->function_num_map);
 	epf->func_no = func_no;

Is set_bit() now setting the correct bit?
I'd guess that:

	epc_group->function_num_map |= 1ul << func_no;

would be more accurate?

David