[PATCH 2/4] hw/block/fdc: Remove the check_media_rate property

[John Snow]

On 2/5/21 1:37 AM, Thomas Huth wrote:
> On 05/02/2021 01.40, John Snow wrote:
>> On 2/3/21 12:18 PM, Thomas Huth wrote:
>>> This was only required for the pc-1.0 and earlier machine types.
>>> Now that these have been removed, we can also drop the corresponding
>>> code from the FDC device.
>>>
>>> Signed-off-by: Thomas Huth <thuth at redhat.com>
>>> ---
>>>   hw/block/fdc.c             | 17 ++---------------
>>>   tests/qemu-iotests/172.out | 35 -----------------------------------
>>>   2 files changed, 2 insertions(+), 50 deletions(-)
>>>
>>> diff --git a/hw/block/fdc.c b/hw/block/fdc.c
>>> index 292ea87805..198940e737 100644
>>> --- a/hw/block/fdc.c
>>> +++ b/hw/block/fdc.c
>>> @@ -874,7 +874,6 @@ struct FDCtrl {
>>>           FloppyDriveType type;
>>>       } qdev_for_drives[MAX_FD];
>>>       int reset_sensei;
>>> -    uint32_t check_media_rate;
>>
>> I am a bit of a dunce when it comes to the compatibility properties... 
>> does this mess with the migration format?
>>
>> I guess it doesn't, since it's not in the VMSTATE declaration.
>>
>> Hmmmm, alright.
> 
> I think that should be fine, yes.
> 
>>>       FloppyDriveType fallback; /* type=auto failure fallback */
>>>       /* Timers state */
>>>       uint8_t timer0;
>>> @@ -1021,18 +1020,10 @@ static const VMStateDescription 
>>> vmstate_fdrive_media_changed = {
>>>       }
>>>   };
>>> -static bool fdrive_media_rate_needed(void *opaque)
>>> -{
>>> -    FDrive *drive = opaque;
>>> -
>>> -    return drive->fdctrl->check_media_rate;
>>> -}
>>> -
>>>   static const VMStateDescription vmstate_fdrive_media_rate = {
>>>       .name = "fdrive/media_rate",
>>>       .version_id = 1,
>>>       .minimum_version_id = 1,
>>> -    .needed = fdrive_media_rate_needed,
>>>       .fields = (VMStateField[]) {
>>>           VMSTATE_UINT8(media_rate, FDrive),
>>>           VMSTATE_END_OF_LIST()
>>> @@ -1689,8 +1680,7 @@ static void fdctrl_start_transfer(FDCtrl 
>>> *fdctrl, int direction)
>>>       /* Check the data rate. If the programmed data rate does not match
>>>        * the currently inserted medium, the operation has to fail. */
>>> -    if (fdctrl->check_media_rate &&
>>> -        (fdctrl->dsr & FD_DSR_DRATEMASK) != cur_drv->media_rate) {
>>> +    if ((fdctrl->dsr & FD_DSR_DRATEMASK) != cur_drv->media_rate) {
>>>           FLOPPY_DPRINTF("data rate mismatch (fdc=%d, media=%d)\n",
>>>                          fdctrl->dsr & FD_DSR_DRATEMASK, 
>>> cur_drv->media_rate);
>>>           fdctrl_stop_transfer(fdctrl, FD_SR0_ABNTERM, FD_SR1_MA, 0x00);
>>> @@ -2489,8 +2479,7 @@ static void fdctrl_result_timer(void *opaque)
>>>           cur_drv->sect = (cur_drv->sect % cur_drv->last_sect) + 1;
>>>       }
>>>       /* READ_ID can't automatically succeed! */
>>> -    if (fdctrl->check_media_rate &&
>>> -        (fdctrl->dsr & FD_DSR_DRATEMASK) != cur_drv->media_rate) {
>>> +    if ((fdctrl->dsr & FD_DSR_DRATEMASK) != cur_drv->media_rate) {
>>>           FLOPPY_DPRINTF("read id rate mismatch (fdc=%d, media=%d)\n",
>>>                          fdctrl->dsr & FD_DSR_DRATEMASK, 
>>> cur_drv->media_rate);
>>>           fdctrl_stop_transfer(fdctrl, FD_SR0_ABNTERM, FD_SR1_MA, 0x00);
>>> @@ -2895,8 +2884,6 @@ static Property isa_fdc_properties[] = {
>>>       DEFINE_PROP_UINT32("dma", FDCtrlISABus, dma, 2),
>>>       DEFINE_PROP_DRIVE("driveA", FDCtrlISABus, 
>>> state.qdev_for_drives[0].blk),
>>>       DEFINE_PROP_DRIVE("driveB", FDCtrlISABus, 
>>> state.qdev_for_drives[1].blk),
>>> -    DEFINE_PROP_BIT("check_media_rate", FDCtrlISABus, 
>>> state.check_media_rate,
>>> -                    0, true),
>>
>> Could you theoretically set this via QOM commands in QMP, and claim 
>> that this is a break in behavior?
>>
>> Though, it's ENTIRELY undocumented, so ... it's probably fine, I 
>> think. Probably. (Please soothe my troubled mind.)
> 
> A user actually could mess with this property even on the command line, 
> e.g. by using:
> 
>   qemu-system-x86_64 -global isa-fdc.check_media_rate=false
> 
> ... but, as you said, it's completely undocumented, the property is 
> really just there for the internal use of machine type compatibility. 
> We've done such clean-ups in the past already, see e.g. 
> c6026998eef382d7ad76 or 2a4dbaf1c0db2453ab78f, so I think this should be 
> fine. But if you disagree, I could replace this by a patch that adds 
> this property to the list of deprecated features instead, so we could at 
> least remove it after it has been deprecated for two releases?
> 

I don't think it's necessary, personally -- just wanted to make sure I 
knew the exact stakes here.

Reviewed-by: John Snow <jsnow at redhat.com>
Acked-by: John Snow <jsnow at redhat.com>