PCI: liveupdate: Document driver binding responsibilities

Document how driver binding works during a Live Update and what the PCI
core expects of drivers and users. Note that this is only a description
of the current division of responsibilities. These can change in the
future if we decide.

Reviewed-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Samiullah Khawaja <skhawaja@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
Link: https://patch.msgid.link/20260918200640.887030-5-dmatlack@google.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/pci/liveupdate.c b/drivers/pci/liveupdate.c
index 00776260ad6f..ec8db86ed66d 100644
--- a/drivers/pci/liveupdate.c
+++ b/drivers/pci/liveupdate.c
@@ -123,6 +123,20 @@
  *
  *  * The device cannot be a Virtual Function (VF).
  *  * The device cannot be behind a PCI-to-PCI bridge.
+ *
+ * Driver Binding
+ * ==============
+ *
+ * In the outgoing kernel, the driver must ensure that it does not release a
+ * device between pci_liveupdate_preserve() and pci_liveupdate_unpreserve().
+ *
+ * In the incoming kernel, the driver must ensure that it does not release a
+ * preserved device between probe() and pci_liveupdate_finish().
+ *
+ * It is the user's responsibility to ensure that incoming preserved devices are
+ * bound to the correct driver. The PCI core does not protect against a device
+ * getting preserved by driver A in the outgoing kernel and then getting bound
+ * to driver B in the incoming kernel.
  */
 
 #define pr_fmt(fmt) "PCI: liveupdate: " fmt