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Commit 92529623 authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Jiri Kosina
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HID: debug: improve hid_debug_event() 



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: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent cc8a9d79

drivers/hid/hid-debug.c

+2 −2
Original line number Diff line number Diff line
@@ -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;