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HID: debug: improve hid_debug_event()

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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>
This commit is contained in:
Rasmus Villemoes 2015-11-24 13:33:47 +01:00 committed by Jiri Kosina
parent cc8a9d7922
commit 92529623d2
1 changed files with 2 additions and 2 deletions
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4
drivers/hid/hid-debug.c
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@ -659,13 +659,13 @@ 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;