[RFC 12/22] dm: add a hidden link to efi object

[Heinrich Schuchardt]

On 10/11/21 16:54, Simon Glass wrote:
> Hi Takahiro,
>
> On Mon, 11 Oct 2021 at 00:43, AKASHI Takahiro
> <takahiro.akashi at linaro.org> wrote:
>>
>> Simon,
>>
>> On Sun, Oct 10, 2021 at 08:14:18AM -0600, Simon Glass wrote:
>>> Hi Takahiro,
>>>
>>> On Thu, 30 Sept 2021 at 23:04, AKASHI Takahiro
>>> <takahiro.akashi at linaro.org> wrote:
>>>>
>>>> This member field in udevice will be used to dereference from udevice
>>>> to efi_object (or efi_handle).
>>>>
>>>> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
>>>> ---
>>>>   include/dm/device.h | 4 ++++
>>>>   1 file changed, 4 insertions(+)
>>>
>>> I think this should be generalised.
>>>
>>> Can we add a simple API for attaching things to devices? Something like:
>>
>> Ok.
>>
>>
>>> config DM_TAG
>>>     bool "Support tags attached to devices"
>>>
>>> enum dm_tag_t {
>>>      DM_TAG_EFI = 0,
>>>
>>>      DM_TAG_COUNT,
>>> };
>>>
>>> ret = dev_tag_set_ptr(dev, DM_TAG_EFI, ptr);
>>>
>>> void *ptr = dev_tag_get_ptr(dev, DM_TAG_EFI);
>>>
>>> ulong val = dev_tag_get_val(dev, DM_TAG_EFI);
>>>
>>> Under the hood I think for now we could have a simple list of tags for
>>> all of DM:
>>>
>>> struct dmtag_node {
>>>     struct list_head sibling;
>>>     struct udevice *dev;
>>>     enum dm_tag_t tag;
>>>     union {
>>>        void *ptr;
>>>        ulong val;
>>>    };
>>> };
>>
>> Just let me make sure; Do you intend that we have a *single* list of tags
>> in the system instead of maintaining a list *per udevice*?
>
> Yes I would prefer not to have a list per udevice, although the API
> could be adjusted to iterate through all tags for a particular
> udevice, if that is needed (dev_tag_first...() dev_tag_next...().

There will never be more than one UEFI handle for one udevice.
We need a single field that points to the the handle if such a handle
exists. But there will be devices for which UEFI protocols don't exist
and where we need no handle. In this case the value can be NULL.

Why should we complicate the picture with a list of tags?

Best regards

Heinrich

>
> Looking at some of your other patches I think you might need to
> support multiple tags for EFI, if there are different things. But
> perhaps a list is necesary.
>
>>
>> -Takahiro Akashi
>>
>>
>>> This can be useful in other situations, for example I think we need to
>>> be able to send an event when a device is probed so that other devices
>>> (with tags attached) can take action. But in any case, it makes the
>>> API separate from the data structure, so aids refactoring later.
>>>
>>> If we find that this is slow we can change the impl, but I doubt it
>>> will matter fornow.
>>>
> [..]
>
> Regards,
> Simon
>