[PATCH 1/1] blk: simplify blk_get_devnum_by_typename()

[Heinrich Schuchardt]

On 10/25/21 19:29, Simon Glass wrote:
> Hi Heinrich,
> 
> On Mon, 25 Oct 2021 at 09:44, Heinrich Schuchardt
> <heinrich.schuchardt at canonical.com> wrote:
>>
>> On 10/25/21 17:18, Simon Glass wrote:
>>> Hi Heinrich,
>>>
>>> On Mon, 25 Oct 2021 at 02:00, Heinrich Schuchardt
>>> <heinrich.schuchardt at canonical.com> wrote:
>>>>
>>>> On 10/25/21 09:54, Heinrich Schuchardt wrote:
>>>>> On 10/24/21 21:54, Simon Glass wrote:
>>>>>> Hi Heinrich,
>>>>>>
>>>>>> On Sat, 23 Oct 2021 at 08:06, Heinrich Schuchardt
>>>>>> <heinrich.schuchardt at canonical.com> wrote:
>>>>>>>
>>>>>>> The block descriptor contains the if_type. There is no need to first
>>>>>>> look
>>>>>>> up the uclass for the if_type and then to check the parent device's
>>>>>>> uclass
>>>>>>> to know if the device has the correct if_type.
>>>>>>>
>>>>>>> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
>>>>>>> ---
>>>>>>>     drivers/block/blk-uclass.c | 35 +----------------------------------
>>>>>>>     1 file changed, 1 insertion(+), 34 deletions(-)
>>>>>>
>>>>>> This seems to be heading in the wrong direction though.
>>>>>>
>>>>>> The IF_TYPE should really go away and be replaced with the UCLASS ID,
>>>>>> I think.
>>>>>>
>>>>>> At present we have lots of calls to blk_create_device_f() which
>>>>>> specify the type. I think we should drop the IF_TYPE_.. arg to that
>>>>>> function and have it figured out from the uclass, in the interim.
>>>>>>
>>>>>> But why do we need IF_TYPE now?
>>>>>
>>>>> I admit that this patch is just an intermediate step.
>>>>>
>>>>> We can replace IF_TYPE by ULASS ID once SPL block devices are always
>>>>> using the driver model. Have we reached this point yet? I have not seen
>>>>> drivers/block/blk_legacy.c being deleted.
>>>>
>>>> qemu_malta64, qemu_malta64el, qemu_malta, qemu_maltael are examples of
>>>> defconfigs requiring drivers/block/blk_legacy.c
>>>
>>> Yes, we seem to have BLK on only for MMC and USB, but malta64 (for
>>> example) uses IDE.
>>>
>>> The problem seems to be HAVE_BLOCK_DEVICE which should not be used.
>>>
>>> +Tom Rini
>>>
>>> Should we remove HAVE_BLOCK_DEVICE at this point, or make it depend on BROKEN?
>>>
>>>>
>>>> Best regards
>>>>
>>>> Heinrich
>>>>
>>>>>
>>>>> Removing if_type_uclass_id[] is anyway on the right path.
>>>
>>> Are you sure? Instead, could we use the uclass ID in more places?
>>
>> Yes, you want to get rid of if_type. This means the table will become
>> obsolete.
> 
> Yes.
> 
>> Once the legacy drivers are removed we can replace all occurrences of
>> if_type by uclass_id. That uclass_id we should not take from blk_desc
>> but from udevice.
> 
> How do we get from a blk_desc to a udevice, though?
> 
> Could you instead look at moving from using blk_desc to using udevice?
> If we had that, I think I can see your point with this patch. At
> present, it looks like a backwards step because you are reducing the
> usage of the uclass and in fact removing it altogether.
> 
> Can you see what I am getting at? Let's move towards migration
> incrementally, not destroy the bridges we have built towards the goal.

Once you move from if_type to uclass_id you will simply replace

   if (desc->if_type != if_type)

by

   if (device_get_uclass_id(dev->uclass->uclass_id) != uclass_id)

Except for this line this patch brings you to the final code.

Best regards

Heinrich