dmaengine: ste_dma40: turn d40_base phy_chans into a flexible array

Convert the separately-offset phy_chans pointer to a C99 flexible array
member at the end of struct d40_base, and switch the allocation to
struct_size(). The log_chans and memcpy_chans slots continue to live
in the same allocation immediately after phy_chans, indexed via
base->log_chans. This removes the hand-rolled pointer fixup that
recomputed phy_chans from base + ALIGN(sizeof(struct d40_base), 4).

The ALIGN(sizeof(struct d40_base), 4) requirement is met implicitly by the
C compiler when using a flexible array member. With struct d40_chan
phy_chans[] as the last member, the C standard guarantees
sizeof(struct d40_base) includes trailing padding to satisfy the alignment
of the flexible array element type (struct d40_chan). Since struct d40_chan
contains members like spinlock_t, pointers, and struct dma_chan — all with
alignment ≥ 4 — the compiler ensures sizeof(struct d40_base) is already a
multiple of _Alignof(struct d40_chan) >= 4. The struct_size() macro then
computes sizeof(struct d40_base) + sizeof(struct d40_chan) * num_phy_chans,
so phy_chans[0] lands at a properly aligned offset without needing the manual
ALIGN.

Assisted-by: Claude:Opus-4.7
Signed-off-by: Rosen Penev <rosenp@gmail.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Link: https://patch.msgid.link/20260531020843.594892-1-rosenp@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

0 files changed, 0 insertions, 0 deletions