On Thu, Aug 22, 2024 at 03:41:10PM -0500, Wei Huang wrote:

Linux has some basic, but incomplete, definition for the TPH Requester
capability registers. Also the definitions of TPH Requester control
register and TPH Completer capability, as well as the ST fields of
MSI-X entry, are missing. Add all required definitions to support TPH
without changing the existing Linux UAPI.

 /* TPH Requester */
 #define PCI_TPH_CAP		4	/* capability register */
-#define  PCI_TPH_CAP_LOC_MASK	0x600	/* location mask */
-#define   PCI_TPH_LOC_NONE	0x000	/* no location */
-#define   PCI_TPH_LOC_CAP	0x200	/* in capability */
-#define   PCI_TPH_LOC_MSIX	0x400	/* in MSI-X */
-#define PCI_TPH_CAP_ST_MASK	0x07FF0000	/* ST table mask */
-#define PCI_TPH_CAP_ST_SHIFT	16	/* ST table shift */
-#define PCI_TPH_BASE_SIZEOF	0xc	/* size with no ST table */
+#define  PCI_TPH_CAP_NO_ST	0x00000001 /* No ST Mode Supported */
+#define  PCI_TPH_CAP_INT_VEC	0x00000002 /* Interrupt Vector Mode Supported */
+#define  PCI_TPH_CAP_DEV_SPEC	0x00000004 /* Device Specific Mode Supported */

I think these modes should all include "ST" to clearly delineate
Steering Tags from the Processing Hints.  E.g.,

  PCI_TPH_CAP_ST_NO_ST       or maybe PCI_TPH_CAP_ST_NONE
  PCI_TPH_CAP_ST_INT_VEC
  PCI_TPH_CAP_ST_DEV_SPEC

+#define  PCI_TPH_CAP_EXT_TPH	0x00000100 /* Ext TPH Requester Supported */
+#define  PCI_TPH_CAP_LOC_MASK	0x00000600 /* ST Table Location */
+#define   PCI_TPH_LOC_NONE	0x00000000 /* Not present */
+#define   PCI_TPH_LOC_CAP	0x00000200 /* In capability */
+#define   PCI_TPH_LOC_MSIX	0x00000400 /* In MSI-X */

These are existing symbols just being tidied, so can't really add "ST"
here unless we just add aliases.  Since they're just used internally,
not by drivers, I think they're fine as-is.

+#define  PCI_TPH_CAP_ST_MASK	0x07FF0000 /* ST Table Size */
+#define  PCI_TPH_CAP_ST_SHIFT	16	/* ST Table Size shift */
+#define PCI_TPH_BASE_SIZEOF	0xc	/* Size with no ST table */
+
+#define PCI_TPH_CTRL		8	/* control register */
+#define  PCI_TPH_CTRL_MODE_SEL_MASK	0x00000007 /* ST Mode Select */
+#define   PCI_TPH_NO_ST_MODE		0x0 /* No ST Mode */
+#define   PCI_TPH_INT_VEC_MODE		0x1 /* Interrupt Vector Mode */
+#define   PCI_TPH_DEV_SPEC_MODE		0x2 /* Device Specific Mode */

These are also internal, but they're new and I think they should also
include "ST" to match the CAP #defines.

Even better, maybe we only add these and use them for both CAP and
CTRL since they're defined with identical values.