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    SubjectRe: [PATCH 2/5] input: Use driver hint to compute the evdev buffer size (rev3)
    Dmitry Torokhov wrote:
    > On Wed, Jun 23, 2010 at 07:07:44PM +0200, Henrik Rydberg wrote:
    >> Hi Ping,
    >> [...]
    >>>> @@ -51,7 +52,9 @@ static DEFINE_MUTEX(evdev_table_mutex);
    >>>>
    >>>> static int evdev_compute_buffer_size(struct input_dev *dev)
    >>>> {
    >>>> - return EVDEV_MIN_BUFFER_SIZE;
    >>>> + int nev = dev->hint_events_per_packet * EVDEV_BUF_PACKETS;
    >>>> + nev = max(nev, EVDEV_MIN_BUFFER_SIZE);
    >>>> + return roundup_pow_of_two(nev);
    >>> I think we have a backward compatibility issue here. This routine will
    >>> return 7 when nev falls to the default value
    >>> (EVDEV_MIN_BUFFER_SIZE/64). This could happen to those drivers that
    >>> don't report MT events or forget/don't feel the need to set
    >>> hint_events_per_packet since the old BUFFER_SIZE worked perfectly for
    >>> them. We need to keep the return value for those drivers as 64 so we
    >>> could allocate the same space as it was in [PATCH 1/5].
    >> Are you perhaps confusing EVDEV_BUF_PACKETS and EVDEV_MIN_BUFFER_SIZE? The last
    >> line ensures that the value returned is a power of two (hence not 7). The
    >> second-to-last line ensures the value is at least equal to 64 (hence not 7). The
    >> default hint value for a driver that does not do anything is zero, which leads
    >> to a return value of 64, just as it is today.
    >>
    >
    > I think Ping might have confused roundup_pow_of_two() with
    > get_order()-type function...
    >
    > Anyways, applied all 5, thanks Henrik.
    >

    Got them, thanks to you too.

    Henrik



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