Hi Dan
On 2015-06-06 18:52 , Dan Carpenter wrote:
> Hi Daniel,
>
> I had a question about patch 5d8926658ce4: "usbtouchscreen: version 0.4"
> from Jul 31, 2006.
That's ancient :)
>
> drivers/input/touchscreen/usbtouchscreen.c
> 1326 static void usbtouch_process_multi(struct usbtouch_usb *usbtouch,
> 1327 unsigned char *pkt, int len)
> 1328 {
> 1329 unsigned char *buffer;
> 1330 int pkt_len, pos, buf_len, tmp;
> 1331
> 1332 /* process buffer */
> 1333 if (unlikely(usbtouch->buf_len)) {
> 1334 /* try to get size */
> 1335 pkt_len = usbtouch->type->get_pkt_len(
> 1336 usbtouch->buffer, usbtouch->buf_len);
>
> ->get_pkt_len() returns -1 on error.
No, it doesn't and never has. In 62aa366d9b015 I added a bit of documentation:
/*
* used to get the packet len. possible return values:
* > 0: packet len
* = 0: skip one byte
* < 0: -return value more bytes needed
*/
int (*get_pkt_len) (unsigned char *pkt, int len);
So -1 means "need one more byte for a complete data packet". That byte will be
in delivered in the next invocation of usbtouch_irq(). One "touchscreen data packet"
can be split across multiple "usb packets" for some devices.
regards
-Daniel
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