lib: add iomem emulation (logic_iomem)

Add IO memory emulation that uses callbacks for read/write to
the allocated regions. The callbacks can be registered by the
users using logic_iomem_alloc().

To use, an architecture must 'select LOGIC_IOMEM' in Kconfig
and then include <asm-generic/logic_io.h> into asm/io.h to get
the __raw_read*/__raw_write* functions.

Optionally, an architecture may 'select LOGIC_IOMEM_FALLBACK'
in which case non-emulated regions will 'fall back' to the
various real_* functions that must then be provided.

Cc: Arnd Bergmann <arnd@kernel.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>

1 files changed, 62 insertions, 0 deletions

diff --git a/include/linux/logic_iomem.h b/include/linux/logic_iomem.h
new file mode 100644
index 000000000000..3fa65c964379
--- /dev/null
+++ b/include/linux/logic_iomem.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2021 Intel Corporation
+ * Author: johannes@sipsolutions.net
+ */
+#ifndef __LOGIC_IOMEM_H
+#define __LOGIC_IOMEM_H
+#include <linux/types.h>
+#include <linux/ioport.h>
+
+/**
+ * struct logic_iomem_ops - emulated IO memory ops
+ * @read: read an 8, 16, 32 or 64 bit quantity from the given offset,
+ *	size is given in bytes (1, 2, 4 or 8)
+ *	(64-bit only necessary if CONFIG_64BIT is set)
+ * @write: write an 8, 16 32 or 64 bit quantity to the given offset,
+ *	size is given in bytes (1, 2, 4 or 8)
+ *	(64-bit only necessary if CONFIG_64BIT is set)
+ * @set: optional, for memset_io()
+ * @copy_from: optional, for memcpy_fromio()
+ * @copy_to: optional, for memcpy_toio()
+ * @unmap: optional, this region is getting unmapped
+ */
+struct logic_iomem_ops {
+	unsigned long (*read)(void *priv, unsigned int offset, int size);
+	void (*write)(void *priv, unsigned int offset, int size,
+		      unsigned long val);
+
+	void (*set)(void *priv, unsigned int offset, u8 value, int size);
+	void (*copy_from)(void *priv, void *buffer, unsigned int offset,
+			  int size);
+	void (*copy_to)(void *priv, unsigned int offset, const void *buffer,
+			int size);
+
+	void (*unmap)(void *priv);
+};
+
+/**
+ * struct logic_iomem_region_ops - ops for an IO memory handler
+ * @map: map a range in the registered IO memory region, must
+ *	fill *ops with the ops and may fill *priv to be passed
+ *	to the ops. The offset is given as the offset into the
+ *	registered resource region.
+ *	The return value is negative for errors, or >= 0 for
+ *	success. On success, the return value is added to the
+ *	offset for later ops, to allow for partial mappings.
+ */
+struct logic_iomem_region_ops {
+	long (*map)(unsigned long offset, size_t size,
+		    const struct logic_iomem_ops **ops,
+		    void **priv);
+};
+
+/**
+ * logic_iomem_add_region - register an IO memory region
+ * @resource: the resource description for this region
+ * @ops: the IO memory mapping ops for this resource
+ */
+int logic_iomem_add_region(struct resource *resource,
+			   const struct logic_iomem_region_ops *ops);
+
+#endif /* __LOGIC_IOMEM_H */