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Diffstat (limited to 'Documentation/core-api/xarray.rst')
| -rw-r--r-- | Documentation/core-api/xarray.rst | 10 |
1 files changed, 7 insertions, 3 deletions
diff --git a/Documentation/core-api/xarray.rst b/Documentation/core-api/xarray.rst index 42bb1a62650f..e90c4925cd37 100644 --- a/Documentation/core-api/xarray.rst +++ b/Documentation/core-api/xarray.rst @@ -131,17 +131,21 @@ If you use :c:func:`DEFINE_XARRAY_ALLOC` to define the XArray, or initialise it by passing ``XA_FLAGS_ALLOC`` to :c:func:`xa_init_flags`, the XArray changes to track whether entries are in use or not. -You can call :c:func:`xa_alloc` to store the entry at any unused index +You can call :c:func:`xa_alloc` to store the entry at an unused index in the XArray. If you need to modify the array from interrupt context, you can use :c:func:`xa_alloc_bh` or :c:func:`xa_alloc_irq` to disable interrupts while allocating the ID. -Using :c:func:`xa_store`, :c:func:`xa_cmpxchg` or :c:func:`xa_insert` -will mark the entry as being allocated. Unlike a normal XArray, storing +Using :c:func:`xa_store`, :c:func:`xa_cmpxchg` or :c:func:`xa_insert` will +also mark the entry as being allocated. Unlike a normal XArray, storing ``NULL`` will mark the entry as being in use, like :c:func:`xa_reserve`. To free an entry, use :c:func:`xa_erase` (or :c:func:`xa_release` if you only want to free the entry if it's ``NULL``). +By default, the lowest free entry is allocated starting from 0. If you +want to allocate entries starting at 1, it is more efficient to use +:c:func:`DEFINE_XARRAY_ALLOC1` or ``XA_FLAGS_ALLOC1``. + You cannot use ``XA_MARK_0`` with an allocating XArray as this mark is used to track whether an entry is free or not. The other marks are available for your use. |