lib: Provide a platform hook to implement vendor specific SBI extensions.

SBI v0.2 specification allows vendor extensions and it should be
implemented in a independent of the core sbi library.

Introduce a single platform callback that will let platforms handle
all vendor extensions in platform specific code if they want.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>

include/sbi/sbi_ecall_interface.h

@@ -38,6 +38,8 @@ enum sbi_ext_base_fid {
 #define SBI_SPEC_VERSION_MAJOR_OFFSET	24
 #define SBI_SPEC_VERSION_MAJOR_MASK	0x7f
 #define SBI_SPEC_VERSION_MINOR_MASK	0xffffff
+#define SBI_EXT_VENDOR_START		0x09000000
+#define SBI_EXT_VENDOR_END		0x09FFFFFF
 /* clang-format on */
 
 #endif

include/sbi/sbi_platform.h

@@ -43,6 +43,8 @@
 
 #include <sbi/sbi_version.h>
 #include <sbi/sbi_scratch.h>
+#include <sbi/sbi_ecall.h>
+#include <sbi/sbi_error.h>
 
 /** Possible feature flags of a platform */
 enum sbi_platform_features {
@@ -112,6 +114,14 @@ struct sbi_platform_operations {
 	int (*system_reboot)(u32 type);
 	/** Shutdown or poweroff the platform */
 	int (*system_shutdown)(u32 type);
+
+	/** platform specific SBI extension implementation probe function */
+	int (*vendor_ext_check)(long extid);
+	/** platform specific SBI extension implementation provider */
+	int (*vendor_ext_provider)(long extid, long funcid,
+			unsigned long *args, unsigned long *out_value,
+			unsigned long *out_trap_cause,
+			unsigned long *out_trap_val);
 } __packed;
 
 /** Representation of a platform */
@@ -506,6 +516,54 @@ static inline int sbi_platform_system_shutdown(const struct sbi_platform *plat,
 	return 0;
 }
 
+/**
+ * Check if a vendor extension is implemented or not.
+ *
+ * @param plat pointer to struct sbi_platform
+ * @param extid	vendor SBI extension id
+ *
+ * @return 0 if extid is not implemented and 1 if implemented
+ */
+static inline int sbi_platform_vendor_ext_check(const struct sbi_platform *plat,
+						long extid)
+{
+	if (plat && sbi_platform_ops(plat)->vendor_ext_check)
+		return sbi_platform_ops(plat)->vendor_ext_check(extid);
+
+	return 0;
+}
+
+/**
+ * Invoke platform specific vendor SBI extension implementation.
+ *
+ * @param plat pointer to struct sbi_platform
+ * @param extid	vendor SBI extension id
+ * @param funcid SBI function id within the extension id
+ * @param args pointer to arguments passed by the caller
+ * @param out_value output value that can be filled the callee
+ * @param out_tcause trap cause that can be filled the callee
+ * @param out_tvalue possible trap value that can be filled the callee
+ *
+ * @return 0 on success and negative error code on failure
+ */
+static inline int sbi_platform_vendor_ext_provider(const struct sbi_platform *plat,
+						   long extid, long funcid,
+						   unsigned long *args,
+						   unsigned long *out_value,
+						   unsigned long *out_tcause,
+						   unsigned long *out_tval)
+{
+	if (plat && sbi_platform_ops(plat)->vendor_ext_provider) {
+		return sbi_platform_ops(plat)->vendor_ext_provider(extid,
+								   funcid, args,
+								  out_value,
+								  out_tcause,
+								  out_tval);
+	}
+
+	return SBI_ENOTSUPP;
+}
+
 #endif
 
 #endif

lib/sbi/sbi_ecall.c

@@ -12,6 +12,7 @@
 #include <sbi/sbi_ecall_interface.h>
 #include <sbi/sbi_error.h>
 #include <sbi/sbi_ipi.h>
+#include <sbi/sbi_platform.h>
 #include <sbi/sbi_system.h>
 #include <sbi/sbi_timer.h>
 #include <sbi/sbi_tlb.h>
@@ -47,14 +48,30 @@ int sbi_check_extension(struct sbi_scratch *scratch, unsigned long extid,
 	 */
 
 	if ((extid >= SBI_EXT_0_1_SET_TIMER &&
-	    extid <= SBI_EXT_0_1_SHUTDOWN) || (extid == SBI_EXT_BASE))
+	    extid <= SBI_EXT_0_1_SHUTDOWN) || (extid == SBI_EXT_BASE)) {
 		*out_val = 1;
-	else
+	} else if (extid >= SBI_EXT_VENDOR_START &&
+		   extid <= SBI_EXT_VENDOR_END) {
+		*out_val = sbi_platform_vendor_ext_check(
+						sbi_platform_ptr(scratch),
+						extid);
+	} else
 		*out_val = 0;
 
 	return 0;
 }
 
+int sbi_ecall_vendor_ext_handler(struct sbi_scratch *scratch,
+				 unsigned long extid, unsigned long funcid,
+				 unsigned long *args, unsigned long *out_val,
+				 unsigned long *out_tcause,
+				 unsigned long *out_tval)
+{
+	return sbi_platform_vendor_ext_provider(sbi_platform_ptr(scratch),
+					       extid, funcid, args, out_val,
+					       out_tcause, out_tval);
+}
+
 int sbi_ecall_base_handler(struct sbi_scratch *scratch, unsigned long extid,
 			   unsigned long funcid, unsigned long *args,
 			   unsigned long *out_val, unsigned long *out_tcause,
@@ -195,8 +212,14 @@ int sbi_ecall_handler(u32 hartid, ulong mcause, struct sbi_trap_regs *regs,
 		ret = sbi_ecall_base_handler(scratch, extension_id, func_id,
 					     args, &out_val,
 					     &out_tval, &out_tcause);
-	else
+	else if (extension_id >= SBI_EXT_VENDOR_START &&
+		extension_id <= SBI_EXT_VENDOR_END) {
+		ret = sbi_ecall_vendor_ext_handler(scratch, extension_id,
+						   func_id, args, &out_val,
+						   &out_tval, &out_tcause);
+	} else {
 		ret = SBI_ENOTSUPP;
+	}
 
 	if (ret == SBI_ETRAP) {
 		sbi_trap_redirect(regs, scratch, regs->mepc,