Flash API: new information getter

[de-nordic]

First commit in this PR proposes change to flash API that introduces API calls for obtaining information about flash, like size, page count and page information.

This change, contrary to flash_api_pages_layout, is non optional addition and does not allow directly returning objects from drivers, instead allows to query the driver to fill in information.

The addition of API calls:

ssize_t flash_get_page_count(const struct device *dev);
ssize_t flash_get_size(const struct device *dev);
int flash_get_page_info(const struct device *dev, off_t offset, struct flash_page_info *fpi);

allows access to information on flash size and page count, and information on single page.
The commit changes also the flash_parameters structure with addition of flags and max_page_size;
there is one flag defined so far: FPF_NON_UNIFORM_LAYOUT that is set for devices with non-uniform layout and should allow code using the flash device to decide how to work with the device.

The second commit is test of changes.

This is proposed implementation of: #36485

Rationale for changes
Original idea has been to implement "virtual" flash device, but the idea has been dropped. Nevertheless the API change allows more efficient checking for device layout.
The main goal of the change is to simplify obtaining information on flash devices, and to be able to define "virtual" devices that could be placed over the other flash devices to perform some actions, which existence of flash_api_pages_layout does allow, as the "virtual" device is not able to easily override values returned by the call.
This change should allow to, for example, define partition or encryption device, that will use the same flash API calls, which means that any function that is able to perform actions on a device of flash type, will be usable with the "virtual" device, without knowing that it is not working on a real device.

Example of the "virtual" device that defines partitions over real device: #36487

TODO:

• test cases;
• apply to all drivers.

[nvlsianpu]

copy from: #36487 (comment)
nvlsianpu:
isn't this similar to flash_get_page_info_by_offs()
de-nordic:
I have added the flash_get_page_info, as a part of #36485, so that it would be possible to override results returned by such call, which is not possible with the current flash_api_get_layout, because it gives direct access to objects defined within driver.
I have not removed the original calls that do layout checks, because this is proposal and I did not want to remove them yet.
The flash_get_page_info_by_offs and the flash_get_page_info_by_idx, and the foreachs, in case of the #36485, would be reimplemented as non-system util library, and the CONFIG that enables them would be still available.
All these functions would be reimplemented around the new flash_get_page_info, flash_get_page_count and flash_get_size.
nvlsianpu:
Ok, understood

[nvlsianpu]

This is all fine to me.

[nvlsianpu]

copy from: #36487 (comment)
nvlsianpu:
this is similar to flash-layout-get implementation api. Shouldn't it be optional?

de-nordic:
I was considering adding this as constant addition as the info is needed anyway, for example you can not do erase without knowing the page info, also this can be used to get alignment as it always returns info for aligned page that contains the offset.
In case of most drivers, the implementation will be quite efficient, because drivers that know about uniform layout will just do something like this:

if (offset < TOTAL_FLASH_SIZE) {
   fpi->offset = offset & ~(CONSTANT_PAGE_SIZE -1);
   fpi->size = CONSTANT_PAGE_SIZE);
}

On the other side the non uniform layout is also quick to obtain:

if (offset < HUGE_PAGE_OFFSET) {
   fpi->offset = offset & ~(CONSTANT_PAGE_SIZE -1);
   fpi->size = CONSTANT_PAGE_SIZE);
} else (offset < TOTAL_FLASH_SIZE) {
   fpi->offset = HUGE_PAGE_OFFSET;
   fpi->size = HUGE_PAGE_SIZE;
}

Because driver exactly knows the layout, in most cases, it does not have to iterate through all pages to get to the offset that is interesting for it.

[nvlsianpu]

I think you are right. Option was introduced when not all devices implements the flash-get-layout API. Nowday it is almost mandatory.

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This pull request has been marked as stale because it has been open (more than) 60 days with no activity. Remove the stale label or add a comment saying that you would like to have the label removed otherwise this pull request will automatically be closed in 14 days. Note, that you can always re-open a closed pull request at any time.