From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1MD9d2-0004KM-IG for qemu-devel@nongnu.org; Sun, 07 Jun 2009 00:05:04 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1MD9cx-0004J1-W5 for qemu-devel@nongnu.org; Sun, 07 Jun 2009 00:05:04 -0400 Received: from [199.232.76.173] (port=38663 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1MD9cx-0004Ip-Tp for qemu-devel@nongnu.org; Sun, 07 Jun 2009 00:04:59 -0400 Received: from mx2.redhat.com ([66.187.237.31]:50331) by monty-python.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1MD9cx-0007OR-C2 for qemu-devel@nongnu.org; Sun, 07 Jun 2009 00:04:59 -0400 Date: Sun, 7 Jun 2009 01:04:10 -0300 From: Marcelo Tosatti Subject: Re: [Qemu-devel] [SOLUTION] "i8042.c: No controller found" -> OS sees no keyboard if I type "in BIOS" Message-ID: <20090607040410.GA25831@amt.cnet> References: <4A0C232D.1020201@wpkg.org> <4A13CDC4.3000704@wpkg.org> <4A1405E1.70405@wpkg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A1405E1.70405@wpkg.org> List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Tomasz Chmielewski , Anthony Liguori Cc: qemu-devel@nongnu.org On Wed, May 20, 2009 at 03:30:09PM +0200, Tomasz Chmielewski wrote: > Tomasz Chmielewski schrieb: > >>> When I boot the guest and type (just hit any keys) in the VNC window >>> before the operating system boots, sometimes, the system loads with >>> no keyboard present - as signified in dmesg on guest: >>> >>> i8042.c: No controller found >>> >>> As a result, I can't use the keyboard in the VNC window. > >> drivers/input/serio/i8042.c in the Linux kerne has this: >> >> static int i8042_controller_check(void) >> { >> if (i8042_flush() == I8042_BUFFER_SIZE) { >> printk(KERN_ERR "i8042.c: No controller found.\n"); >> return -ENODEV; >> } >> >> return 0; >> } >> >> >> So, can it be that if we type anything on keyboard (or move mouse) >> while Qemu's BIOS is still booting or later in the bootloader (GRUB, >> lilo), some buffer is not flushed and Linux gets confused? And as a >> result, decides there is no keyboard? > > Yes, this is what seems to happen - Qemu's keyboard buffer seems to be infinite > or at least very big; normal 8042 devices have buffer of 16 bytes only. > > If we add "i8042.debug" parameter to kernel command line, > we will see how many characters were flushed during boot, i.e.: > > > drivers/input/serio/i8042.c: ff <- i8042 (flush, aux) [0] > drivers/input/serio/i8042.c: 18 <- i8042 (flush, aux) [0] > drivers/input/serio/i8042.c: 92 <- i8042 (flush, aux) [0] > drivers/input/serio/i8042.c: 00 <- i8042 (flush, aux) [0] > (...) > > > With this 16 byte buffer in drivers/input/serio/i8042.h (before 2.6.11 it was > 32 bytes I think): > > #define I8042_BUFFER_SIZE 16 > > > and this piece of code in drivers/input/serio/i8042.c: > > > /* > * i8042_flush() flushes all data that may be in the keyboard and mouse buffers > * of the i8042 down the toilet. > */ > > static int i8042_flush(void) > { > unsigned long flags; > unsigned char data, str; > int i = 0; > > spin_lock_irqsave(&i8042_lock, flags); > > while (((str = i8042_read_status()) & I8042_STR_OBF) && (i < I8042_BUFFER_SIZE)) { > udelay(50); > data = i8042_read_data(); > i++; > dbg("%02x <- i8042 (flush, %s)", data, > str & I8042_STR_AUXDATA ? "aux" : "kbd"); > } > > spin_unlock_irqrestore(&i8042_lock, flags); > > return i; > } > > > > Linux kernel thinks there is no controller: > > > (...) > drivers/input/serio/i8042.c: 28 <- i8042 (flush, aux) [0] > drivers/input/serio/i8042.c: 00 <- i8042 (flush, aux) [0] > i8042.c: No controller found. > > > If we increase "I8042_BUFFER_SIZE" to 256 or more, we have a much better > chance that a booted Linux will have a keyboard present. > > So, who's to be blamed? > > Linux kernel for having its i8042 buffer to small (16 bytes), fixable with: > > > --- i8042.h.orig 2009-05-20 15:26:32.000000000 +0200 > +++ i8042.h 2009-05-20 15:26:32.000000000 +0200 > @@ -73,7 +73,7 @@ > * the i8042 buffers. > */ > > -#define I8042_BUFFER_SIZE 16 > +#define I8042_BUFFER_SIZE 256 > > /* > * Number of AUX ports on controllers supporting active multiplexing > > > > Or Qemu, for having its keyboard buffer too large (I'm not sure, but probably 256 bytes)? All references (*) i could find mention 16 bytes of output buffer (including the Linux source as you mentioned, which was reduced from 32 to 16 somewhere in the 2.6.10 era). http://www.computer-engineering.org/ps2protocol/ http://linux.bkbits.net:8080/linux-2.6.28-stable/drivers/input/serio/i8042.h?PAGE=diffs&REV=4203735dp_doSExYU6ido8KnczbjzQ Reducing PS2_QUEUE_SIZE to 16 also makes the Linux detection loop happy. If QEMU claims to emulate i8042, it should be similar to real hardware. However i'm not familiar with PS/2 or i8042. Anthony?