On Wed, Dec 12, 2012 at 10:58:29AM +0100, Anisse Astier wrote:
> On Tue, 11 Dec 2012 20:27:26 +0200, Maxim Mikityanskiy <maxtram95@xxxxxxxxx> wrote :
>
> > 2012/12/11 Anisse Astier <anisse@xxxxxxxxx>:
> > > On Tue, 11 Dec 2012 19:07:51 +0200, Maxim Mikityanskiy <maxtram95@xxxxxxxxx> wrote :
> > >
> > >> >> @@ -169,11 +169,15 @@ static void msi_wmi_notify(u32 value, void *context)
> > >> >> pr_debug("Eventcode: 0x%x\n", eventcode);
> > >> >> key = sparse_keymap_entry_from_scancode(msi_wmi_input_dev,
> > >> >> eventcode);
> > >> >> - if (key) {
> > >> >> + if (!key) {
> > >> >> + pr_info("Unknown key pressed - %x\n", eventcode);
> > >> >> + goto msi_wmi_notify_exit;
> > >> >> + }
> > >> >> + if (quirk_last_pressed) {
> > >> >> + size_t key_index = key - msi_wmi_keymap;
> > >> > Do you mean key->code - MSI_SCANCODE_BASE ? I'm not sure I understand the
> > >> > intent here otherwise.
> > >>
> > >> msi_wmi_keymap is array of 'struct key_entry', i.e. pointer to array's
> > >> first item. key is a pointer to some array's item. So 'key -
> > >> msi_wmi_keymap' is a difference between pointers, i.e. index of key in
> > >> msi_wmi_keymap.
> > >>
> > >> I do pointer arithmetic here because in patch 12 I add some new
> > >> scancodes, and holes appear in scancode sequence, so we can't just use
> > >> 'key->code - MSI_SCANCODE_BASE' to get item index in array.
> > >
> > > Oh, I see. This is very clever, but a bit too clever. You have no
> > > guarantee, that sparse_keymap_entry_from_scancode will give you a pointer
> > > to *your* key_entry. In fact, it doesn't.
> > >
> > > In sparse_keymap_setup (drivers/input/sparse-keymap.c), the keymap
> > > array(msi_wmi_keymap) is mempcy-ed, at line 187 (kernel ~3.7). So if you
> > > want to use this method, you might need to re-compute the index by
> > > iterating over the elements and comparing key->code for each.
> >
> > Oops, I'm sorry, I was looking only into
> > sparse_keymap_entry_from_scancode() and I didn't discover the fact
> > that dev->keycode is not equal to msi_wmi_keymap. I just wanted to
> > avoid iterating through the array second time. Also, can I use
> > msi_wmi_input_dev->keycode instead of msi_wmi_keymap as array base?
> > input_dev::keycode field is documented at include/linux/input.h:62.
>
> As I said, you could iterate over msi_wmi_keymap and compare key->code to
> each keycode to compute key_index each time.
>
> >
> > It's strange that I didn't get a crash or data corruption on my system
> > when I forced usage of last_pressed for my laptop, loaded this module
> > and tried to press keys.
> >
> > It's very unconvenient that struct key_entry does not have some field
> > for driver-specific extra data. In such field we could store index in
> > last_pressed or event last press time. But we haven't such field.
>
> If that's really needed, such field could be added. Cc-ing Dmitry
> Torokhov to ask what he thinks about altering the sparse keymap API for
> this use case, ie having per key_entry variables to store information,
> here used for debouncing.
> Previously the keymap was contiguous, but we're adding new keys, so it'll
> really be sparse, so we can't use the same trick substraction trick.
A different question - do you really need to store times for all
possible keys or you actually need to know just the last key that was
pressed?
Thanks.
--
Dmitry
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