Add specific cases to device specification #94
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aacuevas
commented
Mar 5, 2025
aacuevas
commented
- Add the specific special case of the NULL device
- Add a specification for detachable devices
- Fixes Create spec for "detachable devices" #77
- Add the specific special case of the NULL device - Add a specification for detachable devices
| (e.g.: a circuit driving an active probe that can be swapped). | ||
| In these cases: | ||
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| - The driver MUST check for the presence of all required hardware elements |
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on reset? Detect when its detacted?
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Good point. On soft reset (as defined in #91), before sending the device table. I'll clarify this.
| @@ -22,3 +22,11 @@ Device ID. Devices sharing an ID are assumed to be the same and share the same | |||
| optionally be divided in two 8-bit values so long as the resulting 16-bit | |||
| integer is unique within a particular “Company” (there is no need for unary | |||
| or monotonic increments when new devices are introduced). | |||
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| .. _null-dev-id: | |||
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Should this go into special devices?
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This is a very good point. I did not think of it as this is not really a device per se, but an indicator of a lack of device.
But on the register map file I mentioned that null devices are the sole exception to devices requiring a register interface.
So maybe it would be better to add all the requirements as a "special device". I would still mention here the special meaning of devid = 0, as it is important enough.
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After reading the current text, I am not so sure right now. The special devices page starts with "There are ... devices that are required to exist". The page defines a couple of things that MUST be present.
However, the null device is a special case to declare a non-device. but it might not necessarily appear.
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maybe its just "special" should be replaced with "required" then.
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I think that we should change "Special Devices" to "Required Devices". I think there should be a short page called Null Device with this description in it. In addition, the text from the Device descriptor page can be moved there as well:
Null Devices
In the special case of :ref:
null devices <null-dev-id>, represented by adevice_id
of 0, all other fields MUST be 0 as these devices MUST NOT produce or consume any kind
of data.
The information on the registers page
.. _null-dev-reg:
Null Devices
An exception to the previously stated register map are :ref:`null devices<null-dev-desc>`, those with a ``device_id`` of :ref:`all zeros <null-dev-id>`. A null device MUST NOT implement any register interface. Any attempt to access a null device MUST return the same error as accessing a non-existing register.
Can be turned into an admonition that references this new null device page.
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I made some edits the the detachable devices page, please review and change as you wish. |
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Ok, I think it should be done now. Please review the last changes, I followed the earlier comments. On the detachable devices page, I do reference the soft reset, we need to link it to the appropriate tag once #91 is merged |
