cxl: Introduce implementation-specific API

The backend API (in cxl.h) lists some low-level functions whose
implementation is different on bare-metal and in a guest. Each
environment implements its own functions, and the common code uses
them through function pointers, defined in cxl_backend_ops

Co-authored-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Signed-off-by: Frederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: Christophe Lombard <clombard@linux.vnet.ibm.com>
Reviewed-by: Manoj Kumar <manoj@linux.vnet.ibm.com>
Acked-by: Ian Munsie <imunsie@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
index 783337d..b8ce29b 100644
--- a/drivers/misc/cxl/file.c
+++ b/drivers/misc/cxl/file.c
@@ -79,7 +79,7 @@
 	if (!afu->current_mode)
 		goto err_put_afu;
 
-	if (!cxl_adapter_link_ok(adapter)) {
+	if (!cxl_ops->link_ok(adapter)) {
 		rc = -EIO;
 		goto err_put_afu;
 	}
@@ -210,8 +210,8 @@
 
 	trace_cxl_attach(ctx, work.work_element_descriptor, work.num_interrupts, amr);
 
-	if ((rc = cxl_attach_process(ctx, false, work.work_element_descriptor,
-				     amr))) {
+	if ((rc = cxl_ops->attach_process(ctx, false, work.work_element_descriptor,
+							amr))) {
 		afu_release_irqs(ctx, ctx);
 		goto out;
 	}
@@ -222,6 +222,7 @@
 	mutex_unlock(&ctx->status_mutex);
 	return rc;
 }
+
 static long afu_ioctl_process_element(struct cxl_context *ctx,
 				      int __user *upe)
 {
@@ -259,7 +260,7 @@
 	if (ctx->status == CLOSED)
 		return -EIO;
 
-	if (!cxl_adapter_link_ok(ctx->afu->adapter))
+	if (!cxl_ops->link_ok(ctx->afu->adapter))
 		return -EIO;
 
 	pr_devel("afu_ioctl\n");
@@ -289,7 +290,7 @@
 	if (ctx->status != STARTED)
 		return -EIO;
 
-	if (!cxl_adapter_link_ok(ctx->afu->adapter))
+	if (!cxl_ops->link_ok(ctx->afu->adapter))
 		return -EIO;
 
 	return cxl_context_iomap(ctx, vm);
@@ -336,7 +337,7 @@
 	int rc;
 	DEFINE_WAIT(wait);
 
-	if (!cxl_adapter_link_ok(ctx->afu->adapter))
+	if (!cxl_ops->link_ok(ctx->afu->adapter))
 		return -EIO;
 
 	if (count < CXL_READ_MIN_SIZE)
@@ -349,7 +350,7 @@
 		if (ctx_event_pending(ctx))
 			break;
 
-		if (!cxl_adapter_link_ok(ctx->afu->adapter)) {
+		if (!cxl_ops->link_ok(ctx->afu->adapter)) {
 			rc = -EIO;
 			goto out;
 		}