Re: [Qemu-devel] [PATCH 2/2] fdc: fix media detection

[Kevin Wolf <kwolf@redhat.com>]

Am 22.05.2012 15:28, schrieb Pavel Hrdina:
> On 05/22/2012 02:01 PM, Kevin Wolf wrote:
>> Am 22.05.2012 12:59, schrieb Pavel Hrdina:
>>> We have to set up 'media_changed' after guest start so floppy driver
>>> could detect that there is no media in drive. For this purpose we call
>>> 'fdctrl_change_cb' instead of 'fd_revalidate' in 'fdctrl_connect_drives'.
>>> 'fd_revalidate' is called inside 'fdctrl_change_cb'.
>>>
>>> In 'fdctrl_handle_seek' we always set current track because we don't care
>>> if there is media inserted or not.
>>>
>>> Signed-off-by: Pavel Hrdina<phrdina@redhat.com>
>> Can you please add a qtest case that shows the problems that you're
>> fixing in this series?
> I'm new to qemu. By "add a qtest case" you mean update tests/fdc-test.c ?

Sorry, I should have been more specific. Yes, that's what I mean.

>>> diff --git a/hw/fdc.c b/hw/fdc.c
>>> index cb4cd25..337b35a 100644
>>> --- a/hw/fdc.c
>>> +++ b/hw/fdc.c
>>> @@ -1617,11 +1617,7 @@ static void fdctrl_handle_seek(FDCtrl *fdctrl, int direction)
>>>       /* The seek command just sends step pulses to the drive and doesn't care if
>>>        * there is a medium inserted of if it's banging the head against the drive.
>>>        */
>>> -    if (fdctrl->fifo[2]>  cur_drv->max_track) {
>>> -        cur_drv->track = cur_drv->max_track;
>>> -    } else {
>>> -        cur_drv->track = fdctrl->fifo[2];
>>> -    }
>>> +    cur_drv->track = fdctrl->fifo[2];
>> Why is it okay to have cur_drv->track point outside the floppy? Won't it
>> mess up future calculations? Not all other places check it again
>> cur_drv->max_track.
>>
>> Kevin
> Well, you are right. Than we have to set 'max_track' even if there is no 
> media. I tested this on bare-metal without media and where floppy driver 
> ask to seek to specific track, it ends good and return specific track 
> position as actual.
> I'll rewrite this behavior and send patch v2.

You mean max_track = 0 isn't a good value to work with? How can a real
drive position the head correctly when it doesn't have a media (and
therefore doesn't know its geometry)?

But if you have a good default value for max_track that we should use
when no medium is present, go ahead.

Kevin