dm: Introduce device sequence numbering

In U-Boot it is pretty common to number devices from 0 and access them
on the command line using this numbering. While it may come to pass that
we will move away from this numbering, the possibility seems remote at
present.

Given that devices within a uclass will have an implied numbering, it
makes sense to build this into driver model as a core feature. The cost
is fairly small in terms of code and data space.

With each uclass having numbered devices we can ask for SPI port 0 or
serial port 1 and receive a single device.

Devices typically request a sequence number using aliases in the device
tree. These are resolved when the device is probed, to deal with conflicts.
Sequence numbers need not be sequential and holes are permitted.

At present there is no support for sequence numbers using static platform
data. It could easily be added to 'struct driver_info' if needed, but it
seems better to add features as we find a use for them, and the use of -1
to mean 'no sequence' makes the default value somewhat painful.

Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/include/dm/uclass-internal.h b/include/dm/uclass-internal.h
index 1434db3..f718f37 100644
--- a/include/dm/uclass-internal.h
+++ b/include/dm/uclass-internal.h
@@ -82,4 +82,27 @@ struct uclass *uclass_find(enum uclass_id key);
  */
 int uclass_destroy(struct uclass *uc);
 
+/**
+ * uclass_find_device_by_seq() - Find uclass device based on ID and sequence
+ *
+ * This searches for a device with the given seq or req_seq.
+ *
+ * For seq, if an active device has this sequence it will be returned.
+ * If there is no such device then this will return -ENODEV.
+ *
+ * For req_seq, if a device (whether activated or not) has this req_seq
+ * value, that device will be returned. This is a strong indication that
+ * the device will receive that sequence when activated.
+ *
+ * The device is NOT probed, it is merely returned.
+ *
+ * @id: ID to look up
+ * @seq_or_req_seq: Sequence number to find (0=first)
+ * @find_req_seq: true to find req_seq, false to find seq
+ * @devp: Returns pointer to device (there is only one per for each seq)
+ * @return 0 if OK, -ve on error
+ */
+int uclass_find_device_by_seq(enum uclass_id id, int seq_or_req_seq,
+			      bool find_req_seq, struct udevice **devp);
+
 #endif