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

[John Snow <jsnow@redhat.com>]

On 2/13/21 5:41 PM, Laurent Vivier wrote:
> Le 08/02/2021 à 08:05, Thomas Huth a écrit :
>> On 05/02/2021 21.15, John Snow wrote:
>>> 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@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@redhat.com>
>>> Acked-by: John Snow <jsnow@redhat.com>
>>
>> Thanks! ... since the first patch has already been merged through Michael's tree, could you then
>> please take this patch here through your floppy / block branch, John? Or maybe it could also go via
>> qemu-trivial?
> 
> Applied to my trivial-patches branch.
> 
> Thanks,
> Laurent
> 

Thank you, Laurent!

--js