linux-kernel - [PATCH -next] pci: fix a -Wtype-limits compilation warning

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Date:   Wed, 18 Dec 2019 12:00:04 -0500
From:   Qian Cai <cai@....pw>
To:     bhelgaas@...gle.com
Cc:     jamessewart@...sta.com, logang@...tatee.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>
Subject: [PATCH -next] pci: fix a -Wtype-limits compilation warning

The commit a7d06153eea2 ("PCI: Fix pci_add_dma_alias() bitmask size")
introduced a compilation warning and a potential infinite loop because
it is no longer possible to be self-terminated as u8 is always less than
256,

In file included from ./include/linux/kernel.h:12,
                 from ./include/asm-generic/bug.h:19,
                 from ./arch/x86/include/asm/bug.h:83,
                 from ./include/linux/bug.h:5,
                 from ./include/linux/jump_label.h:250,
                 from ./arch/x86/include/asm/string_64.h:6,
                 from ./arch/x86/include/asm/string.h:5,
                 from ./include/linux/string.h:20,
                 from ./include/linux/uuid.h:12,
                 from ./include/linux/mod_devicetable.h:13,
                 from ./include/linux/pci.h:27,
                 from drivers/pci/search.c:11:
drivers/pci/search.c: In function 'pci_for_each_dma_alias':
./include/linux/bitops.h:30:13: warning: comparison is always true due
to limited range of data type [-Wtype-limits]
       (bit) < (size);     \
             ^
drivers/pci/search.c:46:3: note: in expansion of macro 'for_each_set_bit'
   for_each_set_bit(devfn, pdev->dma_alias_mask, MAX_NR_DEVFNS) {

Fixed it by using u16 for "devfn" in this occasion.

Fixes: a7d06153eea2 ("PCI: Fix pci_add_dma_alias() bitmask size")
Signed-off-by: Qian Cai <cai@....pw>
---
 drivers/pci/search.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index 9e4dfae47252..42bc44d0e681 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -41,7 +41,7 @@ int pci_for_each_dma_alias(struct pci_dev *pdev,
 	 * DMA, iterate over that too.
 	 */
 	if (unlikely(pdev->dma_alias_mask)) {
-		u8 devfn;
+		u16 devfn;
 
 		for_each_set_bit(devfn, pdev->dma_alias_mask, MAX_NR_DEVFNS) {
 			ret = fn(pdev, PCI_DEVID(pdev->bus->number, devfn),
-- 
2.21.0 (Apple Git-122.2)