Messages in this thread Patch in this message | | | Date | Sun, 08 Apr 2001 22:23:09 +0200 | From | (Gunther Mayer) | Subject | Re: mouse problems in 2.4.2 -> lost byte -> Patch(2.4.3)! |
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Original Problem: PS/2 mouse pointer goes upper right corner and stays there. Diagnosis: one byte was lost and this is fatal for the mouse driver.
Various people wrote: > > On Wed, Mar 28, 2001 at 05:19:33PM -0600, linas@linas.org wrote: .. > > > > > > > I am experiencing debilitating intermittent mouse problems & was about > > > > > > > > > > > > This is easily explained: some byte of the mouse protocol was lost. > > Plus, it's very likely the new PS/2 code will break on some systems that > have not-so-compatible i8042 chips, so it is really something that can't
Losing bytes on psaux is a bug!
We must first understand, how bytes can be lost (most probable first): - transmission error on the line can easily happen in noisy environments and is _not_ handled correctly by linux (i.e. should do RESEND) - 0xAA is always handled as reconnect, if the mouse generates this byte, Linux will de-sync the mouse driver - Mouse is defective or keyboard controller defective - An error in the linux kbd/mouse driver (e.g. triggered by X11<->console switching)
This patch printk's necessary information on the first 2 cases and should be applied to the stable kernel, as this will help to resolve a severe bug !
Regards, Gunther
P.S. These messages can be generated: Apr 8 21:49:23 linux kernel: psaux: reconnect 0xAA detected Apr 8 21:49:42 linux kernel: pc_keyb: mouse error (0x75), byte ignored(ff). Apr 8 21:49:43 linux kernel: psaux: reconnect 0xAA detected
--- linux-2.4.3-orig/drivers/char/pc_keyb.c Wed Apr 4 19:46:42 2001 +++ linux/drivers/char/pc_keyb.c Sun Apr 8 21:45:37 2001 @@ -404,6 +404,11 @@ mouse_reply_expected = 0; } else if(scancode == AUX_RECONNECT){ + // Under normal operation most mice don't generate 0xAA. + // But, Other devices might be unusable with this policy. + // (My mouse easily generates 0xAAs on rapid movements, + // when set to 10 samples/sec.) + printk("psaux: reconnect detected(0xaa), sending AUX_ENABLE.\n"); queue->head = queue->tail = 0; /* Flush input queue */ __aux_write_ack(AUX_ENABLE_DEV); /* ping the mouse :) */ return; @@ -420,6 +425,9 @@ kill_fasync(&queue->fasync, SIGIO, POLL_IN); wake_up_interruptible(&queue->proc_list); } + else + // 2K buffer is enough for about 10 sec under normal operations, here. + printk("psaux: buffer overflow, byte dropped.\n"); } #endif } @@ -465,6 +473,11 @@ else handle_keyboard_event(scancode); } + else + // Fixme: Ignoring bytes will de-sync mouse protocol. + printk("pc_keyb: %s error (0x%02x), byte ignored(%02x).\n", + (status & KBD_STAT_MOUSE_OBF)?"mouse":"kbd",status,scancode); + status = kbd_read_status(); }[unhandled content-type:application/octet-stream]
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