3.16.64-rc1 review patch. If anyone has any objections, please let me know.
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From: Rasmus Villemoes linux@rasmusvillemoes.dk
commit 92529623d242cea4440958d7bcebdf291f4ab15e upstream.
The code in hid_debug_event() causes horrible code generation. First, we do a strlen() call for every byte we copy (we're doing a store to global memory, so gcc has no way of proving that strlen(buf) doesn't change). Second, since both i, list->tail and HID_DEBUG_BUFSIZE have signed type, the modulo computation has to take into account the possibility that list->tail+i is negative, so it's not just a simple and.
Fix the former by simply not doing strlen() at all (we have to load buf[i] anyway, so testing it is almost free) and the latter by changing i to unsigned. This cuts 29% (69 bytes) of the size of the function.
Signed-off-by: Rasmus Villemoes linux@rasmusvillemoes.dk Signed-off-by: Jiri Kosina jkosina@suse.cz Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/hid/hid-debug.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/hid/hid-debug.c +++ b/drivers/hid/hid-debug.c @@ -658,13 +658,13 @@ EXPORT_SYMBOL_GPL(hid_dump_device); /* enqueue string to 'events' ring buffer */ void hid_debug_event(struct hid_device *hdev, char *buf) { - int i; + unsigned i; struct hid_debug_list *list; unsigned long flags;
spin_lock_irqsave(&hdev->debug_list_lock, flags); list_for_each_entry(list, &hdev->debug_list, node) { - for (i = 0; i < strlen(buf); i++) + for (i = 0; buf[i]; i++) list->hid_debug_buf[(list->tail + i) % HID_DEBUG_BUFSIZE] = buf[i]; list->tail = (list->tail + i) % HID_DEBUG_BUFSIZE;