dmaengine: Allow drivers to assign static channel IDs

The dmaengine core assigns channel IDs in registration order. If a driver
skips a hardware channel, chan_id can differ from the hardware numbering
and a client cannot reliably correlate a requested channel with hardware
resources.

Let a driver request an exact channel ID before device registration.
Reserve static IDs through the existing IDA so they remain unique, while
retaining automatic IDA allocation as the default.

For example, idma32 uses chan_id to select DMA_CTL_CH() and
DMA_XBAR_SEL(), so it relies on ascending registration order to match
chan_id with the hardware channel number.

Use direction-flattened IDs for dw-edma channels. Unlike the
direction-local hardware channel number, these IDs are unique within the
DMA device.

Suggested-by: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Koichiro Den <den@valinux.co.jp>
Link: https://lore.kernel.org/r/lm7tadnxsyrypu4mypptlkx5qkytex4qxsijdr5ydud2n3anvf@yakjfjg5ng4u/
Link: https://lore.kernel.org/r/20260813063757.3131865-2-den@valinux.co.jp/
Link: https://lore.kernel.org/r/an4TXwT37vWYEzCn@SMW015318/
Link: https://patch.msgid.link/20260912174023.1227397-2-den@valinux.co.jp
Signed-off-by: Vinod Koul <vkoul@kernel.org>

0 files changed, 0 insertions, 0 deletions