From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:46451) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Sgdv3-0002Bb-Ue for qemu-devel@nongnu.org; Mon, 18 Jun 2012 11:31:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Sgduw-00014b-UW for qemu-devel@nongnu.org; Mon, 18 Jun 2012 11:31:09 -0400 Received: from mx1.redhat.com ([209.132.183.28]:18345) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Sgduv-00014K-NT for qemu-devel@nongnu.org; Mon, 18 Jun 2012 11:31:02 -0400 Message-ID: <4FDF49AD.3040806@redhat.com> Date: Mon, 18 Jun 2012 23:30:53 +0800 From: Amos Kong MIME-Version: 1.0 References: <433764b9-c58b-4b4e-8a4d-0f6cd84a25e7@zmail13.collab.prod.int.phx2.redhat.com> <4FD0326F.3010806@redhat.com> <20120611140642.06be2ee8@doriath.home> <4FD62827.4060900@us.ibm.com> <20120611142546.66871522@doriath.home> <4FD9BB06.3000509@redhat.com> <4FDAE857.6050106@redhat.com> <4FDAEAFD.9090406@redhat.com> <20120615103531.614ed1c7@doriath.home> In-Reply-To: <20120615103531.614ed1c7@doriath.home> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 1/6] qerror: add MAX_KEYCODES 16 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Luiz Capitulino Cc: Anthony Liguori , Gerd Hoffmann , qemu-devel@nongnu.org On 06/15/2012 09:35 PM, Luiz Capitulino wrote: > On Fri, 15 Jun 2012 09:57:49 +0200 > Gerd Hoffmann wrote: > >> Hi, >> >>>> It seems we need to notice user when inputted keys are more than 16. >>> >>> Hi Gerd, >>> >>> When I use 'sendkey' command to send key-series to guest, some keyboard >>> events will be send. There is a limitation (16) that was introduced by this >>> old commit c8256f9d (without description). Do you know the reason? >> >> Probably hardware limitation, ps/2 keyboards can buffer up to 16 keys IIRC. > > Then the perfect thing to do would be to drop the MAX_KEYCODES check from > the sendkey command and move bounds checking down to the device emulation code. > > > However, this will require a bit of code churn if we do it for all devices, > and won't buy us much, as the most likely reason for the error is a client/user > trying to send too many keys in parallel to the guest, right? Agree, we can notice in stderr when the redundant keys are ignored as hid. #define QUEUE_LENGTH 16 /* should be enough for a triple-click */ static void hid_keyboard_event(void *opaque, int keycode) { ... if (hs->n == QUEUE_LENGTH) { fprintf(stderr, "usb-kbd: warning: key event queue full\n"); return; } > If this is right, then I think that the best thing to do would be to drop the > MAX_KEYCODES check from the sendkey command and document that devices can drop > keys if too many of them are sent in parallel or too fast (we can mention ps/2 > as an example of a 16 bytes limit). > >> >> Likewise the usb hid devices can buffer up to 16 events. In that case >> it is just a qemu implementation detail and not a property of the >> hardware we are emulating, so it can be changed. Not trivially though >> as the buffer is part of the migration data, so it is more work that >> just changing a #define. -- Amos.