github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-31 10:33:41 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

usb: xhci: correct debug message page size calculation

Browse Source 
The ffs() function returns the index of the first set bit, starting from 1.
If no bits are set, it returns zero. This behavior causes an off-by-one
page size in the debug message, as the page size calculation [1]
is zero-based, while ffs() is one-based.

Fix this by subtracting one from the result of ffs(). Note that since
variable 'val' is unsigned, subtracting one from zero will result in the
maximum unsigned integer value. Consequently, the condition 'if (val < 16)'
will still function correctly.

[1], Page size: (2^(n+12)), where 'n' is the set page size bit.

Fixes: 81720ec532 ("usb: host: xhci: use ffs() in xhci_mem_init()")
Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20250306144954.3507700-9-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Niklas Neronin 2025-03-06 16:49:47 +02:00 committed by Greg Kroah-Hartman
parent fe1ccba52a
commit 55741c7233
1 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/usb/host/xhci-mem.c
View File

@ -2391,10 +2391,10 @@ int xhci_mem_init(struct xhci_hcd *xhci, gfp_t flags)
page_size = readl(&xhci->op_regs->page_size);
xhci_dbg_trace(xhci, trace_xhci_dbg_init,
"Supported page size register = 0x%x", page_size);
i = ffs(page_size);
if (i < 16)
val = ffs(page_size) - 1;
if (val < 16)
xhci_dbg_trace(xhci, trace_xhci_dbg_init,
"Supported page size of %iK", (1 << (i+12)) / 1024);
"Supported page size of %iK", (1 << (val + 12)) / 1024);
else
xhci_warn(xhci, "WARN: no supported page size\n");
/* Use 4K pages, since that's common and the minimum the HC supports */