Re: [PATCH 4/7] Input: ALPS - Remove assumptions about packet size

Seth Forshee
2011-10-31T18:17:07Z

On Sun, Oct 30, 2011 at 11:36:19AM -0400, Chase Douglas wrote:
> On 10/26/2011 05:14 PM, Seth Forshee wrote:
> > In preparation for version 4 protocol support, which has 8-byte
> > data packets, remove all hard-coded assumptions about packet size
> > and use psmouse->pktsize instead.
> >
> > Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
> > ---
> > drivers/input/mouse/alps.c | 27 ++++++++++++++++++---------
> > 1 files changed, 18 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/input/mouse/alps.c b/drivers/input/mouse/alps.c
> > index 572cb21..14d1f64 100644
> > --- a/drivers/input/mouse/alps.c
> > +++ b/drivers/input/mouse/alps.c
> > @@ -315,7 +315,7 @@ static void alps_flush_packet(unsigned long data)
> >
> > serio_pause_rx(psmouse->ps2dev.serio);
> >
> > - if (psmouse->pktcnt == 6) {
> > + if (psmouse->pktcnt == psmouse->pktsize) {
> >
> > /*
> > * We did not any more data in reasonable amount of time.
> > @@ -365,15 +365,15 @@ static psmouse_ret_t alps_process_byte(struct psmouse *psmouse)
> > return PSMOUSE_BAD_DATA;
> > }
> >
> > - /* Bytes 2 - 6 should have 0 in the highest bit */
> > - if (psmouse->pktcnt >= 2 && psmouse->pktcnt <= 6 &&
> > + /* Bytes 2 - pktsize should have 0 in the highest bit */
> > + if (psmouse->pktcnt >= 2 && psmouse->pktcnt <= psmouse->pktsize &&
> > (psmouse->packet[psmouse->pktcnt - 1] & 0x80)) {
> > dbg("refusing packet[%i] = %x\n",
> > psmouse->pktcnt - 1, psmouse->packet[psmouse->pktcnt - 1]);
> > return PSMOUSE_BAD_DATA;
> > }
> >
> > - if (psmouse->pktcnt == 6) {
> > + if (psmouse->pktcnt == psmouse->pktsize) {
> > alps_process_packet(psmouse);
> > return PSMOUSE_FULL_PACKET;
> > }
> > @@ -531,8 +531,13 @@ static int alps_tap_mode(struct psmouse *psmouse, int enable)
> > static int alps_poll(struct psmouse *psmouse)
> > {
> > struct alps_data *priv = psmouse->private;
> > - unsigned char buf[6];
> > + unsigned char *buf;
> > bool poll_failed;
> > + int ret = -1;
> > +
> > + buf = kmalloc(psmouse->pktsize, GFP_KERNEL);
> > + if (!buf)
> > + return -1;
>
> Can we preallocate a buffer somewhere instead of allocating every time
> we enter the function? If we know the maximum packet size we could
> allocate on the stack instead.

Thanks for pointing that out; I had meant to come back and do something
about this but forgot. I was hoping to avoid having to hard-code an
assumed maximum packet size. I'll take a look at it.